During A01-9 we found ~25 Black Hole X-ray Novae (BHXNe) in M31 using Chandra, and with HST follow-up have estimated orbital periods for 9 of these. Observations are under way 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 over 800ks (ACIS+HRC) near the M31 bulge by the end of A10, and total Chandra exposure on M31 is now almost 1Msec. By continuing our monitoring program through AO12 we will reach ~950ks on the bulge and >1Msec total Chandra M31 exposure.

we will observe for 2 orbits 'on', and then 6 months later 2 orbits 'off', in a mode to get the max s/n for a faint point source in a crowded, bright field (=M31) 12 false 0.0 0.0 false false false false SUPPORTED STAR X-RAY NOVAE J2000 J2000 STAR X-RAY NOVAE Visit 1 holding position, to be updated 3 to 4 weeks before execution. J2000 J2000 POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 1 false Timing link suitability includes constraints ([06 After 01 by 180.0 to 210.0 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. visit 1 for chandra c11, only to be activated if a bright transient is found by Chandra 3 to 4 weeks in advance of this visit 1291875126000 87.63083576104111 (Tic-Visit :proposal-id 12014 :visit-id "01" :proposal-version -1 :trans-version "20090702" :date "22-Oct-2009 15:16:22.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12014 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12014 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3018 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3351 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12014 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3128 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3351 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. visit2 for chandra c11, only to be activated if a bright transient is found by Chandra 3 to 4 weeks in advance of this visit (Tic-Visit :proposal-id 12014 :visit-id "02" :proposal-version -1 :trans-version "20110509" :date "22-Jun-2011 11:17:26.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12014 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12014 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2858 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3341 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12014 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2976 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3341 :pcs-gap 0 ) true 2 0