AROUND 200 NEW X-RAY BINARY IDs FROM 13 YR OF CHANDRA OBSERVATIONS OF THE M31 CENTER

We have created 0.3-10 keV, 13 yr, unabsorbed luminosity lightcurves for 528 X-ray sources in the central 20' of M31. We have 174 Chandra observations spaced at similar to 1 month intervals due to our transient monitoring program, deeper observations of the M31 nucleus, and some public data from other surveys. We created 0.5-4.5 keV 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 greater than or similar to 10(35) erg s(-1) 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 similar to 200 new identifications. This result represents great progress over the similar to 50 XBs and similar to 40 XB candidates previously identified out of the similar to 2000 X-ray sources within the D-25 region of M31; it also demonstrates the power of SF analysis for identifying XBs in external galaxies. We also identify a new transient black hole candidate, associated with the M31 globular cluster B128.