12 years of X-ray variability in M31 globular clusters, including 8 black hole candidates, as seen by Chandra

Understand

We examined 134 Chandra observations of the population of X-ray sources associated with globular clusters (GCs) in the central region of M31.

• These are expected to be X-ray binary systems (XBs), consisting of a neutron star or black hole accreting material from a close companion.
• We created long-term lightcurves for these sources, correcting for background, interstellar absorption and instrumental effects.
• We tested for variability by examining the goodness of fit for the best fit constant intensity.