X-ray binaries observed in M31 with Chandra

We have 174 Chandra observations spaced at ~1 month intervals due to our transient monitoring program, deeper observations of the M31 nucleus, and some public data from other surveys. We created 0.5-4.5keV structure functions (SFs) for each source for comparison with the ensemble SF of active galactic nuclei (AGN).

We find 220 X-ray sources with luminosities >~10^35^erg/s that have SFs with significantly more variability than the ensemble AGN SF, and which are likely X-ray binaries (XBs). A further 30 X-ray sources were identified as XBs using other methods. We therefore have 250 probable XBs in total, including ~200 new identifications.