We have been carring out a Chandra (GO+GTO) and HST (GO) program to find Black Hole X-ray Nova (BHXN) and their optical counterparts in M31 for several years. To date we have found >2 dozen BHXN and 3 HST optical counterparts for these BHXN. Our results suggest a rather high ratio of BH to neutron star (NS) binaries, or a high duty cycle for the BHXN. We propose to continue this program, with the goal of determining the orbital period distribution and duty cycles of these BHXN. Current results yield 3 orbital periods and 3 upper limits. Our proposed observations will ~double the total number of periods and therefore yield sufficient numbers to make a first approximation of the orbital period distribution. The orbital period distribution is the fundamental observable parameter any binary stellar evolution models must match, and the duty cycle is very poorly known but directly influences the binary lifetime. M31 is the only galaxy in which this extra-galactic study of BHXN is feasible. Furthermore, the 2 HST observations will allow us to estimate the orbital period of a single super-Eddington source.

We will use the ACS 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 (5 from the AO8, plus the last observation from AO7). 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. As we will not know the exact location of our target until a Chandra observation is completed, we cannot provide final coordinates for our object until about 3 weeks prior to the first observation. As a result, we have currently supplied the coordinates of the nucleus of M31 as a hold position, to be corrected to the final position when we detect the BHXN. This detection will be within 1 degree of the M31 nucleus. 12 false 0.0 0.0 false false false false false false SUPPORTED UNIDENTIFIED OPTICAL EMITTER ULTRAVIOLET EMITTER X-RAY EMITTER J2000 00 00 0.0000 +00 00 0.00 J2000 UNIDENTIFIED OPTICAL EMITTER ULTRAVIOLET EMITTER X-RAY EMITTER J2000 00 00 0.0000 +00 00 0.00 J2000 POS-TARG DITHER 0.559017 LINE 0.559017 false false 143.1301 4 26.56505 WFPC2-BOX 1 false POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 2 false 1235289731000 40.58415618586599 (Tic-Visit :proposal-id 11013 :visit-id "15" :proposal-version -1 :trans-version "20070709" :date "15-Oct-2007 14:34:04.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 179264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11013 :visit-id "15" :obset-id "15" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11013 :visit-id "15" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2780 :al-overhead-at-end 100 :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 11013 :visit-id "15" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :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 11013 :visit-id "16" :proposal-version -1 :trans-version "20090130" :date "19-May-2009 10:15:13.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 179264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11013 :visit-id "16" :obset-id "16" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11013 :visit-id "16" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2780 :al-overhead-at-end 100 :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 11013 :visit-id "16" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :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 11013 :visit-id "17" :proposal-version -1 :trans-version "20090130" :date "19-May-2009 10:15:50.0" :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 11013 :visit-id "17" :obset-id "17" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11013 :visit-id "17" :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 11013 :visit-id "17" :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