During A01-8 we found ~20 Black Hole X-ray Novae (BHXNe) in M31 using Chandra, and with HST follow-up have estimated orbital periods for 8 of these. Observations are underway with HST to attempt to estimate additional periods. We propose to continue this program concentrating our scarce HST resources on a single transient which exceeds 1e38 erg/s. Only uninterrupted monitoring can yield the duty cycles and long-term light curves of BHXNe (and other variables) in M31. Our GO+GTO programs will have accumulated 790ks (ACIS+HRC) near the M31 bulge by the end of AO9, and total Chandra exposure on M31 is now 940ks. By continuing our monitoring program through AO12 we will reach ~950ks on the bulge and >1Msec total Chandra M31 exposure.

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