https://gsawg.wiki.ast.cam.ac.uk/api.php?action=feedcontributions&user=Jure.Japelj&feedformat=atomGaia Science Alerts Working Group - User contributions [en]2024-03-29T09:31:02ZUser contributionsMediaWiki 1.35.14https://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=993Triggers:Flares2011-09-11T14:03:34Z<p>Jure.Japelj: /* Spectrum examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]<br />
<br />
[[File:M_star_spectrum.png|thumb|450px|border|center|Spectrum of an M6 dwarf is extremely red. From [http://www.sdss3.org/dr8/data_access.php SDSS DR8]]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=992Triggers:Flares2011-09-11T14:03:00Z<p>Jure.Japelj: /* Spectrum examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]<br />
<br />
[[File:M_star_spectrum.png|thumb|450px|border|right|Spectrum of an M6 dwarf is extremely red. From [http://www.sdss3.org/dr8/data_access.php SDSS DR8]]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=991Triggers:Flares2011-09-11T14:02:44Z<p>Jure.Japelj: /* Spectrum examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]<br />
<br />
[[File:M_flare_spectrum.png|thumb|450px|border|right|Spectrum of an M6 dwarf is extremely red. From [http://www.sdss3.org/dr8/data_access.php SDSS DR8]]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=990Triggers:Flares2011-09-11T14:02:25Z<p>Jure.Japelj: /* Spectrum examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]<br />
<br />
[[File:m_flare_spectrum.png|thumb|450px|border|right|Spectrum of an M6 dwarf is extremely red. From [http://www.sdss3.org/dr8/data_access.php SDSS DR8]]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=989Triggers:Flares2011-09-11T14:01:55Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]<br />
<br />
[[File:m_flare_spectrum.png|thumb|450px|border|right|Spectrum of an M6 dwarf is extremely red. From [http://www.sdss3.org/dr8/data_access.php SDSS DR8]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:M_star_spectrum.png&diff=988File:M star spectrum.png2011-09-11T13:59:35Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=987Triggers:Flares2011-09-08T10:05:27Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|center|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=986Triggers:Flares2011-09-08T10:03:55Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
\vspace{5.0cm}<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=985Triggers:Flares2011-09-08T10:01:35Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
== Spectrum examples ==<br />
<br />
[[File:yzcmi_spec.png|thumb|450px|border|left|Example of a flare spectrum with an excess of radiation at short wavelengths and pronounced Balmer emission lines. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Yzcmi_spec.png&diff=984File:Yzcmi spec.png2011-09-08T09:58:57Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=983Triggers:Flares2011-09-08T09:54:59Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|550px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|350px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Yzcmi.png&diff=982File:Yzcmi.png2011-09-08T09:54:03Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=981Triggers:Flares2011-09-08T09:52:44Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|450px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:yzcmi.png|thumb|450px|border|right|The YZ Cmi U-band flare. From [http://adsabs.harvard.edu/abs/2010ApJ...714L..98K Kowalski 2010]]]<br />
<br />
[[File:cn_leo.png|thumb|450px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=980Triggers:Flares2011-09-08T09:48:25Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|450px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:cn_leo.png|thumb|450px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|450px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=979Triggers:Flares2011-09-08T09:48:00Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|400px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B Bopp & Moffett 1973.]]]<br />
<br />
[[File:cn_leo.png|thumb|400px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=978Triggers:Flares2011-09-08T09:47:18Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:uv_ceti.png|thumb|400px|border|left|High temporal resolution observations of a flare from UV Cet star. From [http://adsabs.harvard.edu/abs/1973ApJ...185..239B] Bopp & Moffett 1973.]]<br />
<br />
[[File:cn_leo.png|thumb|400px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=977Triggers:Flares2011-09-08T09:43:52Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:cn_leo.png|thumb|400px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=976Triggers:Flares2011-09-08T09:43:24Z<p>Jure.Japelj: /* Light curve examples */</p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:FlareCNLeo-PioftheSky.png|400px]] Example flare detected by Pi of the Sky project. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:cn_leo.png|thumb|400px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=975Triggers:Flares2011-09-08T09:43:02Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:FlareCNLeo-PioftheSky.png|400px]] Example flare detected by Pi of the Sky project. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:cn:leo.png|thumb|400px|border|left|Outburst of the flare star CN Leo. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Cn_leo.png&diff=974File:Cn leo.png2011-09-08T09:41:12Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=973Triggers:Flares2011-09-08T09:38:20Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:FlareCNLeo-PioftheSky.png|400px]] Example flare detected by Pi of the Sky project. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:FlareGJ3331A-PioftheSky.png|400px]] High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:gj3332.png|thumb|400px|border|right|High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].]]</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Uv_ceti.png&diff=972File:Uv ceti.png2011-09-08T09:36:09Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Gj3332.png&diff=971File:Gj3332.png2011-09-08T09:35:54Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=970Triggers:GRBs2011-09-08T09:34:28Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occurring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the light curve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow light curves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow light curves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical light curves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F5.png|thumb|400px|border|right|GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitudes. In the case of OAs, the results are given for two different circumburst environments.]]<br />
<br />
[[File:F6.png|thumb|400px|border|right|Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results are given for a time of five years.]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occurring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details on the simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top figure for the case of on-axis and orphan afterglows. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, right figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the left. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (though it will be smaller for brighter sources [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected GRB optical afterglow detections with Gaia satellite during it's five years of expected operation is of the order of a few tens. Most of the expected detections are of the orphan afterglows, while the possibility of an on-axis afterglow detection is small (less than 10). The problem of afterglow recognition and poor time sampling of the light curve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F10.png|thumb|400px|border|center|Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distribution of the change in magnitude in the time in which an orphan afterglow is in the field of view. Black distribution corresponds to detection after the peak in a light curve while red distribution corresponds to detection before the peak.]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, Gaia Alerts Workshop 2011, [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Talks/gaia_alerts_japelj.pdf presentation] and [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Movies/Japelj-GRBs.mov video recording] of the talk: The detectability of GRB optical counterparts with Gaia<br />
*J. Japelj, A. Gomboc, 2011, [http://arxiv.org/abs/1107.2858 arXiv:1107.2858]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure.Japelj]] 11:18, 15 July 2011 (BST)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=969Triggers:Flares2011-09-08T09:32:41Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
== Light curve examples == <br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:FlareCNLeo-PioftheSky.png|400px]] Example flare detected by Pi of the Sky project. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:FlareGJ3331A-PioftheSky.png|400px]] High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:Flares&diff=968Triggers:Flares2011-09-08T09:31:14Z<p>Jure.Japelj: </p>
<hr />
<div>=== M dwarf flares ===<br />
<br />
Statistical study of M dwarf flares in Stripe 82 is presented in [http://arxiv.org/abs/0906.2030 Kowalski et al. 2009].<br />
<br />
[[File:Flare_example_Stripe82.png|400px|right]]<br />
<br />
* Colour range for M-dwarfs (r − i) > 0.53 and (i − z) > 0.3 and (u-r) > 3<br />
* The most flaring are late type M-dwarfs (M4-M6), earlier types (M2-M3) flare half as often as late types and M0-M1 dwarfs flare only 20% as often as late types.<br />
* flares are the most pronounced in u-band<br />
* around 35% of M-dwarfs are in binary systems - these have bluer u-g. Most single M-dwarfs will have u-g > 1.8<br />
* g - K > 4 - significantly brighter in IR (2MASS cross-match) than Visual.<br />
* amplitude in u > 0.7 mag up to 5 mag.<br />
* large and small flares possible on the same star<br />
* flaring fraction: 0.0108%, i.e. 1 of every 10,000 observation of a M-dwarf in Stripe 82 resulted in a flare<br />
* Sloan (5yrs) flaring star probabilities for different types of Mdwarf: M0-M1: 38/35,000; M2-M3: 79/13,000; M4-M6: 119/2120. <br />
* 1.3 flares per hour sq.deg with <math>\Delta u > 0.7</math> mag, with slightly more flares towards the galactic plane.<br />
<br />
[[File:Mflares-rates.png|400px|left]]<br />
<br />
[[File:FlaresStripe82.png|400px|Ampitude distribution for Stripe82 flares.]]<br />
<br />
<br />
[[File:Mdwarf_flare_Gl234AB.png|600px]] Example of flares in Gl234AB (V577 Mon) from [http://ukads.nottingham.ac.uk/abs/1989A%26A...208..208D Doyle et al. 1989]<br />
<br />
[[File:FlareCNLeo-PioftheSky.png|400px]] Example flare detected by Pi of the Sky project. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].<br />
<br />
[[File:FlareGJ3331A-PioftheSky.png|400px]] High temporal resolution observations of a flare star by Pi of the Sky. From [http://arxiv.org/abs/0810.1179 Sokolowski 2008].</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=962Triggers:GRBs2011-07-15T10:18:30Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F5.png|thumb|400px|border|right|GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitudes. In the case of OAs, the results are given for two different circumburst environments.]]<br />
<br />
[[File:F6.png|thumb|400px|border|right|Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results are given for a time of five years.]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details on the simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top figure for the case of on-axis and orphan afterglows. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, right figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the left. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (though it will be smaller for brighter sources [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected GRB optical afterglow detections with Gaia satellite during it's five years of expected operation is of the order of a few tens. Most of the expected detections are of the orphan afterglows, while the possibility of an on-axis afterglow detection is small (less than 10). The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F10.png|thumb|400px|border|center|Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distribution of the change in magnitude in the time in which an orphan afterglow is in the field of view. Black distribution corresponds to detection after the peak in a lightcurve while red distribution corresponds to detection before the peak.]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, Gaia Alerts Workshop 2011, [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Talks/gaia_alerts_japelj.pdf presentation] and [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Movies/Japelj-GRBs.mov video recording] of the talk: The detectability of GRB optical counterparts with Gaia<br />
*J. Japelj, A. Gomboc, 2011, [http://arxiv.org/abs/1107.2858 arXiv:1107.2858]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure.Japelj]] 11:18, 15 July 2011 (BST)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=961Triggers:GRBs2011-07-15T10:14:24Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F5.png|thumb|400px|border|right|GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitudes. In the case of OAs, the results are given for two different circumburst environments.]]<br />
<br />
[[File:F6.png|thumb|400px|border|right|Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results are given for a time of five years.]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details on the simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top figure for the case of on-axis and orphan afterglows. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (though it will be smaller for brighter sources [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected GRB optical afterglow detections with Gaia satellite during it's five years of expected operation is of the order of a few tens. Most of the expected detections are of the orphan afterglows, while the possibility of an on-axis afterglow detection is small (less than 10). The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F10.png|thumb|400px|border|center|Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distribution of the change in magnitude in the time in which an orphan afterglow is in the field of view. Black distribution corresponds to detection after the peak in a lightcurve while red distribution corresponds to detection before the peak.]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, Gaia Alerts Workshop 2011, [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Talks/gaia_alerts_japelj.pdf presentation] and [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Movies/Japelj-GRBs.mov video recording] of the talk: The detectability of GRB optical counterparts with Gaia<br />
*J. Japelj, A. Gomboc, 2011, [http://arxiv.org/abs/1107.2858 arXiv:1107.2858]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=960Triggers:GRBs2011-07-15T10:13:42Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F5.jpg|thumb|400px|border|right|GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitudes. In the case of OAs, the results are given for two different circumburst environments.]]<br />
<br />
[[File:F6.jpg|thumb|400px|border|right|Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results are given for a time of five years.]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details on the simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top figure for the case of on-axis and orphan afterglows. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (though it will be smaller for brighter sources [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected GRB optical afterglow detections with Gaia satellite during it's five years of expected operation is of the order of a few tens. Most of the expected detections are of the orphan afterglows, while the possibility of an on-axis afterglow detection is small (less than 10). The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F10.jpg|thumb|400px|border|center|Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distribution of the change in magnitude in the time in which an orphan afterglow is in the field of view. Black distribution corresponds to detection after the peak in a lightcurve while red distribution corresponds to detection before the peak.]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, Gaia Alerts Workshop 2011, [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Talks/gaia_alerts_japelj.pdf presentation] and [http://www.ast.cam.ac.uk/~wyrzykow/GAIA/GSAW2011/Movies/Japelj-GRBs.mov video recording] of the talk: The detectability of GRB optical counterparts with Gaia<br />
*J. Japelj, A. Gomboc, 2011, [http://arxiv.org/abs/1107.2858 arXiv:1107.2858]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:F10.png&diff=959File:F10.png2011-07-15T10:02:33Z<p>Jure.Japelj: Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distrib</p>
<hr />
<div>Left: Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change of magnitude in the time in which an afterglow is in the entire field of view (red) for the on-axis case. Right: Distribution of the change in magnitude in the time in which an orphan afterglow is in the field of view. Black distribution corresponds to detection after the peak in a lightcurve while red distribution corresponds to detection before the peak.</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:F6.png&diff=958File:F6.png2011-07-15T10:01:53Z<p>Jure.Japelj: Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results</p>
<hr />
<div>Distribution of magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (grey) and magnitudes of afterglows detected by the second telescope (red) in the case of on-axis simulation. The results are given for a time of five years.</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:F5.png&diff=957File:F5.png2011-07-15T10:00:56Z<p>Jure.Japelj: GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitude. In the case of OAs, the results are given for two different circumburst environments.</p>
<hr />
<div>GRB on-axis and OAs detection rate in five years of Gaia's operation as a function of limiting magnitude. In the case of OAs, the results are given for two different circumburst environments.</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=851Triggers:GRBs2011-04-05T13:14:06Z<p>Jure.Japelj: /* Simulation references */</p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, [http://www.fmf.uni-lj.si/~gomboc/report.pdf The estimation of detectability of on-axis GRB optical afterglows with Gaia]<br />
*J. Japelj, A. Gomboc, 2011, [http://www.fmf.uni-lj.si/~gomboc/reportOA.pdf The estimation of detectability of GRB optical orphan afterglows with Gaia]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=850Triggers:GRBs2011-04-05T13:13:28Z<p>Jure.Japelj: /* Simulation references */</p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, [http://www.fmf.uni-lj.si/~gomboc/report.pdf The estimation of detectability of on-axis GRB optical afterglows with Gaia]<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia <br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=849Triggers:GRBs2011-04-05T13:10:53Z<p>Jure.Japelj: /* Simulation references */</p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/report.pdf download]<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia <br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=848Triggers:GRBs2011-04-05T13:10:30Z<p>Jure.Japelj: /* Simulation references */</p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
[http://www.fmf.uni-lj.si/~gomboc/report.pdf download]<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia <br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=847Triggers:GRBs2011-04-05T12:07:44Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia <br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=846Triggers:GRBs2011-04-05T12:06:59Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia [http://www.rssd.esa.int/index.php?project=GAIA&page=index<br />
download]<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/reportOA.pdf<br />
download]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=845Triggers:GRBs2011-04-05T12:05:57Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/report.pdf<br />
download]<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/reportOA.pdf<br />
download]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=844Triggers:GRBs2011-04-05T12:04:55Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/report.pdf<br />
(download)]<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia [http://www.fmf.uni-lj.si/~gomboc/reportOA.pdf<br />
(download)]<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=843Triggers:GRBs2011-03-31T19:08:37Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<br />
<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=842Triggers:GRBs2011-03-31T19:07:35Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle [[File:thetaobs.png]] between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when [[File:theta1.png]]. In the case of [[File:theta2.png]], we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Theta2.png&diff=841File:Theta2.png2011-03-31T19:06:23Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Theta1.png&diff=840File:Theta1.png2011-03-31T19:06:10Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Thetaobs.png&diff=839File:Thetaobs.png2011-03-31T19:05:56Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=838Triggers:GRBs2011-03-31T19:02:59Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle [[File:theta.png]]. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle $\theta_{\rm obs}$ between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when $\theta_{\rm obs} < \theta_{\rm j}$. In the case of $\theta_{\rm obs} > \theta_{\rm j}$, we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=File:Theta.png&diff=837File:Theta.png2011-03-31T19:02:15Z<p>Jure.Japelj: </p>
<hr />
<div></div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=836Triggers:GRBs2011-03-31T19:01:32Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle \theta_{j}. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle $\theta_{\rm obs}$ between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when $\theta_{\rm obs} < \theta_{\rm j}$. In the case of $\theta_{\rm obs} > \theta_{\rm j}$, we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=835Triggers:GRBs2011-03-31T18:58:53Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle \theta_{j}. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle $\theta_{\rm obs}$ between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when $\theta_{\rm obs} < \theta_{\rm j}$. In the case of $\theta_{\rm obs} > \theta_{\rm j}$, we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<math>T \propto R^{-3/4}</math><br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japeljhttps://gsawg.wiki.ast.cam.ac.uk/index.php?title=Triggers:GRBs&diff=834Triggers:GRBs2011-03-31T18:58:31Z<p>Jure.Japelj: </p>
<hr />
<div>=== Gamma-Ray Burst Optical Afterglows ===<br />
<br />
[[File:GRB-schematic_lightcurve.png|350px|border|right]]<br />
<br />
Gamma-ray bursts (GRBs) are extremely energetic, brief and unpredictable explosions occuring on cosmological distances. They represent the most luminous events in the gamma-ray part of the electromagnetic spectrum known in the universe. Often, the prompt gamma-ray emission is followed by an afterglow emitted at longer wavelengths (from X-rays to radio), which can last for several days. Comprehensive review on GRBs and their physics can be found in [http://adsabs.harvard.edu/abs/2004RvMP...76.1143P Piran 2004] or [http://adsabs.harvard.edu/abs/2006RPPh...69.2259M Meszaros 2006].<br />
<br />
GRB explosions are believed to be collimated, rather than spherical [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007]. Thus the material, ejected by the explosion, is expanding in the form of a bimodal jet, characterized by an initial half-opening angle \theta_{j}. The shape of the lightcurve depends on the relative position of the observer's line-of-sight and the axis of the jet cone. We can describe that with an angle $\theta_{\rm obs}$ between both directions. We talk about an on-axis GRB and a 'regular' optical afterglow when $\theta_{\rm obs} < \theta_{\rm j}$. In the case of $\theta_{\rm obs} > \theta_{\rm j}$, we can not observe the prompt gamma-ray emission. Due to the beaming effect, we could still observe the so called orphan afterglow (details in [http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] or ). A schematic afterglow lightcurves for different jet half-opening angles and viewing angles are shown in figure on the right.<br />
<br />
[[File:kann.png|thumb|350px|border|left|A large sample of regular (on-axis) optical afterglow lightcurves, corrected for Galactic extinction [http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010].]]<br />
<br />
A large sample of observed optical lightcurves of regular 'on-axis' afterglows is shown in figure on the left ([http://adsabs.harvard.edu/abs/2010ApJ...720.1513K Kann et al. 2010]).<br />
<br />
Observations made by the Swift satellite imply that there are approximately 300 on-axis GRBs per year for which we could observe an optical afterglow. <br />
<br />
[[File:Color-oa.png|thumb|325px|border|right|Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]..]]<br />
<br />
Even though orphan afterglows have not been conclusively detected yet, they have been studied a great deal over the last 15 years and various estimations on their detectability have been made ([http://adsabs.harvard.edu/abs/2007RMxAC..27..140G Granot 2007] and references therein).<br />
<br />
It has been observed, that the color indices (R - I), (V -R) and (B - V) of a sample of observed afterglows are roughly constant in the first 10 days of observation, i.e. their time evolution is negligible. This property could serve as a mean to recognize an afterglow and to distinguish it from other possible sources [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004]. Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs is shown in figure on the right. All the color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for E(B-V) = 0.5 mag are shown; they show how much and where the observed data point would move without proper correction (even erroneous correction would thus shift the point only slightly and in predictable direction). Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Šimon et al. 2001] [http://adsabs.harvard.edu/abs/2004AIPC..727..487S Šimon et al. 2004] where a detailed information can be found.<br />
<br />
== Detecting GRBs with Gaia ==<br />
<br />
[[File:F1.jpg|thumb|400px|border|right|The average GRB on-axis afterglow detection rate in respect to limiting magnitude in five years.]]<br />
<br />
[[File:F2.jpg|thumb|400px|border|right|The average GRB orphan-afterglow detection rate in five years in the case of two different circumburst environments.]]<br />
<br />
[[File:F4.jpg|thumb|400px|border|right|Distribution of the change in magnitude in 4.4 s (corresponding to an observation with 2 successive CCDs) (black) and the change during the afterglow presence in the field of view (gray).]]<br />
<br />
In order to predict the number of optical afterglow detections with Gaia in five years of it's time of operation, a simulation was performed. The simulation took into account a scanning law of Gaia, it's field of view, etc. It consists of two parts: one for regular 'on-axis' afterglows and the other for orphan afterglows. In the former the observational data were used to constrain the parameters needed in the simulation (i.e. initial afterglow magnitude distribution, number of afterglows occuring in five years, etc.), while in the latter the parameters were obtained from theoretical predictions. Details of on-axis and orphan afterglow simulation are given in [[#Simulation references|simulation references]]. <br />
<br />
Number of detections in respect to limiting magnitude are shown on the the right in the top and the middle figure for the case of on-axis and orphan afterglows, respectively. The average GRB orphan-afterglow detection rate has been simulated for two different circumburst environments.<br />
<br />
Bottom, left figure shows initial magnitude distribution of detected on-axis afterglows (black), same distribution at the time of the first detection (gray) and the distribution of detections with the second telescope. Similar plot for orphan afterglows is given in [[#Simulation references|references]].<br />
<br />
Since GRB afterglows are initially rapidly fading and they will be observed for 4.4 seconds by each CCD camera, the change of magnitude in that time could in principle be observable. For all detected afterglows in our simulations, we therefore calculated the change of magnitude in 4.4 s, corresponding to observations by two successive CCDs, and also for observations lasting as long as a specific afterglow is in the telescope's field of view. The distribution of the change of magnitude for both cases is shown in the bottom figure on the right. Since the expected photometric error of Gaia at $M_{\rm lim} = 20$ mag will be 10 mmag at best (but probably bigger [http://www.rssd.esa.int/index.php?project=GAIA&page=index ESA]), the chances of observing the change in magnitudes will be small.<br />
<br />
To summarize: the number of expected orphan afterglow detections with the Gaia satellite during it's five years of expected operation is of the order of 10. Adding the results of the on-axis afterglows simulation, the number of expected optical afterglow detections in five years is slightly increased. The problem of afterglow recognition and poor time sampling of the lightcurve, in addition to the small number of expected detections, makes the study of GRB optical afterglows with Gaia difficult. On the other hand, since orphan afterglows have not been conclusively detected yet, a possible detection would provide valuable new data.<br />
<br />
[[File:F3.jpg|thumb|400px|border|center|Distribution of initial magnitudes, which are associated with detected afterglows (black), same magnitudes at the time of the first detection (gray) and magnitudes of afterglows detected also by the second telescope (red).]]<br />
<br />
== Simulation references ==<br />
<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of on-axis GRB optical afterglows with Gaia<br />
*J. Japelj, A. Gomboc, 2011, The estimation of detectability of GRB optical orphan afterglows with Gaia<br />
<math>T \propto R^{-3/3}</math><br />
<br />
[[User:Jure.Japelj|Jure Japelj]] 18:09, 31 March 2011 (UTC)</div>Jure.Japelj