Triggers:RCrB

R Corona Borealis stars

Only around 50 known in the Galaxy and Magellanic Clouds.

Characteristics:

• sudden and non-periodic drops in magnitude
• drops by up to 8 magnitudes
• some small variation in the baseline
• the "dark" stage can last from days to years
• recovers slowly to the baseline

Example of RCrB star in the LMC as seen by OGLE-II

DY Persei

Some people claim it is a similar type to RCrB, however the drops in magnitude are much smaller and seem to be periodical (P~1000d).

Example light curve of DY Per-type candidate