Gaia Science Alerts Working Group - User contributions [en]

Triggers:GRBs

2009-12-09T11:46:34Z

Vojtechsimon:

[[File:GRB-schematic_lightcurve.png|300px|right]]

Short-lived optical transients associated with enormous gamma-ray outbursts GRBs.
A catalogue of GRBs is available [http://grad40.as.utexas.edu here].
Comprehensive recent review on GRBs and their physics can be found in [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

* Time-scales of the gamma-ray emission range from a fraction of second to several minutes. This emission is often accompanied by the so-called optical afterglow which can last for several days. Optical afterglows can be therefore detected with Gaia even several days after the GRB trigger.
* Optical afterglow can reach up to few mag in maximum, but the whole range of magnitudes observed at a given time elapsed from the GRB largely differs for the individual events (more than 3 mag). These optical afterglows often display specific color indices with negligible time evolution, which helps distinguish them from other kinds of transients by photometric observations using several color filters.
* Host galaxy of GRB can be visible, but its apprent magnitude is usually fainter than the detection limit of Gaia (about 20 mag). Nevertheless, this host galaxy can often be detected by large ground-based telescopes at the position of the optical afterglow.

[[File:GRB06-RAPTOR.png|400px]] from [http://ukads.nottingham.ac.uk/abs/2006ApJ...642L..99W Wozniak et al. 2006]

[[File:GRB08-PI.png|400px]] from [http://arxiv.org/abs/0903.2998 Sokolowski et al.2009]

== Detecting GRBs with Gaia ==

[[File:plot_grb_eff.png|400px|Thumb|right|Gaia detection efficiency for GRBs in per cents.]]

About 5% of GRBs is detectable by Gaia, with the highest efficiency close to the nodes. The main feature visible in the data is steady and rapid decline over AF CCDs. Time sampling at AF CCDs level is 4.4s per CCD.
We also demand the transient to be visible in the second FOV (after 105 min).

[[File:plot_grb_mag_15.png|400px|left]]

[[File:plot_grb_mag.png|400px|right]]

[[File:GRB-fraction.png|300px]] from [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

[[File:Color-oa.png|400px|left]]

Color-color (''B-V'' vs. ''V-R'') diagram of optical afterglows of long GRBs. 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 ([http://adsabs.harvard.edu/abs/2001A%26A...377..450S Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004]) 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 Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004], where a detailed information can be found.

Triggers:CVs

2009-12-08T14:58:54Z

Vojtechsimon:

Cataclysmic variables (CVs) are very active objects and their long-term activity is extremely complex. No two CVs display identical activity. The current state of art explains this variety as a result of two dominant physical processes – variations of the mass transfer rate d''m''/d''t'' with time (i.e. changes of the amount of matter which is being transferred from the companion star (donor) to the WD), and the thermal instability of the accretion disk. It emerges that the complicated profiles of the light curves basicly result from a combination of these two mechanisms (e.g. [http://adsabs.harvard.edu/abs/1995CAS....28.....W Warner, 1995]).

The basic systematics of the long-term activity in CVs, can be arranged in the following way, as shown in the following three panels. From top to bottom panel, the character of this activity changes from large-amplitude, isolated outbursts starting from the low baseline brightness to the dominant relatively small fluctuations in the high state.

[[File:Types-of-CVs.png|400px|]]

== Basic properties of the long-term activity in various kinds of CVs ==

The basic observable parameters of the long-term brightness variations can be summarized in the following way. Time-averaged d''m''/d''t'' increases in the sequence:

''Dwarf novae of U Gem type''

''Dwarf novae of Z Cam type''

''Novalike''

(Dwarf novae of SU UMa type are CVs with very short orbital period (mostly less than 2 hours). Their activity is similar to U Gem type, but they display two types of outburst - normal outbursts and superoutbursts.)

* '''Dwarf novae of U Gem type – rare outbursts'''
**Typical duration of outburst: days to weeks
**Typical recurrence time (cycle-length) of outbursts: weeks to years
**Typical amplitude of outburst: 2-7 mag

*'''Dwarf novae of SU UMa type'''
**Typical duration of a normal outburst: days
**Typical recurrence time (cycle-length) of normal outbursts: weeks to years
**Typical amplitude of a normal outburst: 2-3 mag
**Typical duration of a superoutburst: two weeks
**Typical recurrence time (cycle-length) of superoutbursts: weeks to years
**Typical amplitude of a superoutburst: 3-5 mag

*'''Dwarf novae of Z Cam type'''
**Typical duration of outburst: days to 1 week
**Typical recurrence time (cycle-length) of outbursts: weeks
**Typical amplitude of outburst: 2-3 mag

*'''Novalike and VY Scl type systems'''
**Typical timescale of fluctuations: days to weeks
**Typical amplitude of fluctuations: 0.5-1 mag
**Typical amplitude of high/low state transitions: 1-4 mag

== VY Sculptoris ==
A subclass of cataclysmic variables exhibiting occasional drops by several magnitudes at irregular intervals. The prototype of the class had shown a deep low-state in 2008, first since 1983 ([http://uk.arxiv.org/abs/0910.0475 Greiner et al. 2009]).

[[File:CV-VYScl.png|300px|right]]

* amplitude: several magnitudes
* drop time scale: 10-30 days
* low state lasts for about 100 days
* some periodicity (P about 10 days) is present
* mechanism not well understood
* some of VY Scl stars are supersoft X-ray sources during optical low-states.
* V504 Cen has period of 4.21h and went down by 6 mag in 2006 and remained in it for nearly a year.

Triggers:CVs

2009-12-08T14:34:29Z

Vojtechsimon:

Triggers:CVs

2009-12-08T14:15:00Z

Vojtechsimon:

Triggers:CVs

2009-12-08T13:00:44Z

Vojtechsimon:

There is a very large variety of behaviours of CVs.

[[File:Types-of-CVs.png|400px|]]

== VY Sculptoris ==
A subclass of cataclysmic variables exhibiting occasional drops by several magnitudes at irregular intervals. The prototype of the class had shown a deep low-state in 2008, first since 1983 ([http://uk.arxiv.org/abs/0910.0475 Greiner et al. 2009]).

[[File:CV-VYScl.png|300px|right]]

* amplitude: several magnitudes
* drop time scale: 10-30 days
* low state lasts for about 100 days
* some periodicity (P about 10 days) is present
* mechanism not well understood
* some of VY Scl stars are supersoft X-ray sources during optical low-states.
* V504 Cen has period of 4.21h and went down by 6 mag in 2006 and remained in it for nearly a year.

File:Types-of-CVs.png

2009-12-08T12:57:59Z

Vojtechsimon: Types of CVs according to the increasing mass transfer rate

Types of CVs according to the increasing mass transfer rate

Triggers

2009-12-08T10:31:46Z

Vojtechsimon:

''' Please expand this section with your favourite types of possible alerts. The most useful information would be the number statistics, amplitude and timescale, example light curve, spectrum and the reasoning for an rapid alert.'''

===Possible triggers for Science Alerts===

* [[Triggers:Supernovae | Supernovae]]

* [[Triggers:LensedSNe | Gravitationally lensed supernovae]]

* [[Triggers:GRBs | Gamma Ray Bursts Optical Counterparts]]

* [[Triggers:LBVs | Luminous Blue Variables]]

* [[Triggers:CNe | Classical novae]]

* [[Triggers:DNe | Dwarf novae]]

* [[Triggers:Microlensing | Microlensing events]]

* [[Triggers:Flares | M-dwarf flares]]

* [[Triggers:RCrB | R Coronae Borealis type variables (dimming objects)]]

* [[Triggers:CVs | Cataclysmic Variables (CVs)]]

* [[Triggers:XBs | X-ray binaries (XBs)]]

* [[Triggers:FUOri | FU Orionis-type eruptive stars]]

* [[Triggers:TTau | T Tauri type pre-main sequence stars]]

* [[Triggers:Other | Other rare transients]]

== Table of transients ==
This table is based on [http://arxiv.org/abs/0906.5355 Rau et al. 2009] on Palomar Transient Factory (PTF).
MR is an absolute magnitude in R, tau is time of a decline by 2 mag.
Note, these are not all the types of transites Gaia will detect.

{| border="1" cellspacing="0" cellpadding="5" align="center"
! Class
! MR
! tau
! Universal rate
! Gaia rate
|-
| Dwarf Novae
| 9..4
| 3..20
| <math>3\times10^{-5} \textrm{pc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Classical Novae
| -5..-10
|2..100
|<math>2\times10^{-10} \textrm{yr}^{-1}\textrm{L}_{\odot,K}^{-1}</math>
|
|-
|Luminous Red Novae
| -10..-14
|20..60
|<math>1.5\times10^{-13} \textrm{yr}^{-1}\textrm{L}_{\odot,K}^{-1}</math>
|
|-
|Fallback SNe
| -4..-21
|0.5..2
|<math>10^{-13} \textrm{yr}^{-1}\textrm{L}_{\odot,K}^{-1}</math>
|
|-
|Macronovae
| -13..-15
|0.3..3
|<math>10^{-4..-8} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|SN .Ia
| -15..-17
|2..5
|<math>(4..10)\times 10^{-6} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|SNe Ia
| -17..-19.5
|30..70
|<math>3\times 10^{-5} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Tidal disruption flares
| -15..-19
|30..350
|<math>10^{-6} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Core-collapse SNe
| -14..-21
|20..300
|<math>5\times 10^{-5} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Luminous SNe
| -19..-23
|50..400
|<math>10^{-7} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Orphan afterglows (SGRB)
| -14..-18
|5..15
|<math>3\times 10^{-7..-9} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|Orphan afterglows (LGRB)
| -22..-26
|2..15
|<math>3\times 10^{-7..-9} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|On-axis LGRB afterglows
| ..-37
|1..15
|<math>4\times 10^{-10} \textrm{Mpc}^{-3} \textrm{yr}^{-1}</math>
|
|-
|}

----
== CMD of selected variables and transients ==
CMD paths of various types of variable stars, including Be stars, R CrB and V4334 Sgr. From [http://arxiv.org/abs/0907.4090 Spano et al. 2009]

[[File:VariablesPathsCMDLMC.png|650px]]

----
== Time scales and amplitudes ==
[[File:Kulkarni-absmag-timescale.png|400px|left|thumb|Absolute magnitude vs timescale of novae, supernovae and some of new transients. From Kulkarni (2009).]]

[[File:plot_transients_tau_ampl.png|400px]]
[[File:plot_transients_trise_ampl.png|400px]]
[[File:plot_transients_tdecline_ampl.png|400px]]
[[File:plot_transients_trise_tdecline.png|400px]]

Triggers:GRBs

2009-12-08T10:27:00Z

Vojtechsimon:

[[File:GRB-schematic_lightcurve.png|300px|right]]

Short-lived optical transients associated with enormous gamma-ray outbursts GRBs.
A catalogue of GRBs is available [http://grad40.as.utexas.edu here].
Comprehensive recent review on GRBs and their physics can be found in [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

* Time-scales of the gamma-ray emission range from a fraction of second to several minutes. This emission is often accompanied by the so-called optical afterglow which can last for several days.
* Optical afterglow can reach up to few mag in maximum, but the whole range of magnitudes observed at a given time elapsed from the GRB largely differs for the individual events (more than 3 mag). These optical afterglows often display specific color indices with negligible time evolution, which helps distinguish them from other kinds of transients.
* Host galaxy of GRB can be visible, but its apprent magnitude is usually fainter than the detection limit of Gaia (about 20 mag). Nevertheless, this host galaxy can often be detected by large ground-based telescopes at the position of the optical afterglow.

[[File:GRB06-RAPTOR.png|400px]] from [http://ukads.nottingham.ac.uk/abs/2006ApJ...642L..99W Wozniak et al. 2006]

[[File:GRB08-PI.png|400px]] from [http://arxiv.org/abs/0903.2998 Sokolowski et al.2009]

== Detecting GRBs with Gaia ==

[[File:plot_grb_eff.png|400px|Thumb|right|Gaia detection efficiency for GRBs in per cents.]]

About 5% of GRBs is detectable by Gaia, with the highest efficiency close to the nodes. The main feature visible in the data is steady and rapid decline over AF CCDs. Time sampling at AF CCDs level is 4.4s per CCD.
We also demand the transient to be visible in the second FOV (after 105 min).

[[File:plot_grb_mag_15.png|400px|left]]

[[File:plot_grb_mag.png|400px|right]]

[[File:GRB-fraction.png|300px]] from [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

[[File:Color-oa.png|400px|left]]

Color-color (''B-V'' vs. ''V-R'') diagram of optical afterglows of long GRBs. 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 ([http://adsabs.harvard.edu/abs/2001A%26A...377..450S Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004]) 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. Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004], where a detailed information can be found.

People

2009-12-08T09:59:26Z

Vojtechsimon:

==People contributing to the Science Alerts Working Group==
''Add your name here if you contribute.''

* Institute of Astronomy, Cambridge, UK
** [[user:Lukasz|Lukasz Wyrzykowski]]
** [[user:STH | Simon Hodgkin]]
** [[user:Vasily | Vasily Belokurov]]
* Astronomical Institute, AS CR, Czech Republic
** [[Vojtech Simon]]

Triggers:GRBs

2009-12-08T09:56:01Z

Vojtechsimon:

[[File:GRB-schematic_lightcurve.png|300px|right]]

Very short-lived optical transients associated with enormous gamma-ray outbursts.
A catalogue of GRBs is available [http://grad40.as.utexas.edu here].
Comprehensive recent review on GRBs and their physics can be found in [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

* time-scales from seconds to minutes
* in maximum can reach up to few mag, but the whole range observed
* host galaxy can be visible

[[File:GRB06-RAPTOR.png|400px]] from [http://ukads.nottingham.ac.uk/abs/2006ApJ...642L..99W Wozniak et al. 2006]

[[File:GRB08-PI.png|400px]] from [http://arxiv.org/abs/0903.2998 Sokolowski et al.2009]

== Detecting GRBs with Gaia ==

[[File:plot_grb_eff.png|400px|Thumb|right|Gaia detection efficiency for GRBs in per cents.]]

About 5% of GRBs is detectable by Gaia, with the highest efficiency close to the nodes. The main feature visible in the data is steady and rapid decline over AF CCDs. Time sampling at AF CCDs level is 4.4s per CCD.
We also demand the transient to be visible in the second FOV (after 105 min).

[[File:plot_grb_mag_15.png|400px|left]]

[[File:plot_grb_mag.png|400px|right]]

[[File:GRB-fraction.png|300px]] from [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

[[File:Color-oa.png|400px|left]]

Color-color (''B-V'' vs. ''V-R'') diagram of optical afterglows of long GRBs. 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 ([http://adsabs.harvard.edu/abs/2001A%26A...377..450S Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004]) 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. Adapted from [http://adsabs.harvard.edu/abs/2001A%26A...377..450S Simon et al., 2001], [http://adsabs.harvard.edu/abs/2004AIPC..727..487S 2004], where a detailed information can be found.

Triggers:GRBs

2009-12-08T09:44:26Z

Vojtechsimon:

[[File:GRB-schematic_lightcurve.png|300px|right]]

Very short-lived optical transients associated with enormous gamma-ray outbursts.
A catalogue of GRBs is available [http://grad40.as.utexas.edu here].
Comprehensive recent review on GRBs and their physics can be found in [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

* time-scales from seconds to minutes
* in maximum can reach up to few mag, but the whole range observed
* host galaxy can be visible

[[File:GRB06-RAPTOR.png|400px]] from [http://ukads.nottingham.ac.uk/abs/2006ApJ...642L..99W Wozniak et al. 2006]

[[File:GRB08-PI.png|400px]] from [http://arxiv.org/abs/0903.2998 Sokolowski et al.2009]

== Detecting GRBs with Gaia ==

[[File:plot_grb_eff.png|400px|Thumb|right|Gaia detection efficiency for GRBs in per cents.]]

About 5% of GRBs is detectable by Gaia, with the highest efficiency close to the nodes. The main feature visible in the data is steady and rapid decline over AF CCDs. Time sampling at AF CCDs level is 4.4s per CCD.
We also demand the transient to be visible in the second FOV (after 105 min).

[[File:plot_grb_mag_15.png|400px|left]]

[[File:plot_grb_mag.png|400px|right]]

[[File:GRB-fraction.png|300px]] from [http://prola.aps.org/abstract/RMP/v76/i4/p1143_1 Piran,2005]

[[File:Color-oa.png|400px|left]]

Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs. 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 (Simon , Sim04} 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. Adapted from Simon et al. (2001, 2004), where a detailed information can be found.

File:Color-oa.png

2009-12-08T08:58:34Z

Vojtechsimon: Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs. 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

Color-color (B-V vs. V-R) diagram of optical afterglows of long GRBs. 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 (Simon et al. 2001, 2004} 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. Adapted from Simon et al. (2001, 2004), where a detailed information can be found.