During A01-7 we found >16 Black Hole X-ray Novae (BHXN) in M31 using Chandra, and with HST followup have estimated orbital periods for 6 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 the NS Eddington limit. Only uninterrupted monitoring can yield the duty cycles and long-term lightcurves of BHXN (and other variables) in M31. Our GO+GTO programs have accumulated 300ks (ACIS) near the M31 bulge, and total ACIS exposure on M31 is now 620ks. Our monitoring program alone can amass 500ks on the bulge if continued through AO12, and combined with other programs will reach >1Msec ACIS exposure on the bulge.

We will use the WFPC2 camera to obtain images of an active Black Hole X-ray Nova (BHXN) in M31. This BHXNe will be chosen from one of 6 Chandra-ACIS observations from the AO9. We will wait until a super-Eddington source is detected (Lx > 3e38 erg/s) to trigger the first HST observation, which will take place ~4 weeks later; this will capture the counterpart in a bright optical state. A second HST observation will be carried out ~6 months later to study the source in quiesence. 12 false 0.0 0.0 false false false false false false SUPPORTED UNIDENTIFIED OPTICAL EMITTER ULTRAVIOLET EMITTER X-RAY EMITTER J2000 00 42 44.3000 +41 16 9.00 J2000 WFPC2 Imaging No WFPC2 Imaging No POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 2 false (Tic-Visit :proposal-id 11338 :visit-id "15" :proposal-version -1 :trans-version "20090130" :date "19-May-2009 10:57:50.0" :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 2273792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11338 :visit-id "15" :obset-id "15" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11338 :visit-id "15" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2834 :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 3169 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11338 :visit-id "15" :orbit-number 2 :pcs-time 195 :si-vis-utilization 2752 :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 3169 :pcs-gap 0 ) false 2 0 (Tic-Visit :proposal-id 11338 :visit-id "16" :proposal-version -1 :trans-version "20090130" :date "19-May-2009 10:57:58.0" :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 2273792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11338 :visit-id "16" :obset-id "16" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11338 :visit-id "16" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2834 :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 3169 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11338 :visit-id "16" :orbit-number 2 :pcs-time 195 :si-vis-utilization 2752 :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 3169 :pcs-gap 0 ) false 2 0