Finding a consistent explanation for the behavior of all the kinds of transient behavior observed is an active area of astronomical research. Such systems have helped us gain knowledge about fundamental astrophysical parameters such as stellar sizes and masses. Such objects have provided us with knowledge of stellar structure, dynamics, and evolution. The timescales can range from milliseconds to years. Some of the variations are regularly spaced in time, such as those due to the rotation period of the compact object in a binary or the revolution period of one star around another.
Some variations are completely aperiodic, that is they recur at random times.
This might be due to a sudden variation in the stellar wind from the normal star or a sudden mass ejection from the normal star. Typically, transients reach their maximum intensity in about a week and decline back to undetectability in a month or two. The change in intensity is typically a factor of 1000 or more. The recurrence timescale is years. Show me a printable version of this page.