Detecting Isolated Black Holes through Astrometric Microlensing

Visit 7 ready, which needs to execute between Sep 1 and Sep 15, 2012. This is the second of the two orbits that TTRB had approved to be exchanged from 12586. ----- Attempting Submission 3 (Wed Apr 11 16:49:51 GMT 2012) ----- ----- Attempting Submission 4 (Wed Apr 25 15:41:44 GMT 2012) ----- ----- Attempting Submission 5 (Tue Aug 07 14:35:07 GMT 2012) ----- Already run. Detecting Isolated Black Holes through Astrometric Microlensing This proposal aims to make the first detection of isolated stellar-mass black holes (BHs) in the Milky Way, and to determine their masses. Until now, the only directly measured BH masses have come from radial-velocity measurements of X-ray binaries. Our proposed method uses the astrometric shifts that occur when a Galactic-bulge microlensing event is caused by a BH lens. Out of the hundreds of bulge microlensing events found annually by the OGLE and MOA surveys, a few are found to have very long durations (>200 days). It is generally believed that the majority of these long-duration events are caused by lenses that are isolated BHs. To test this hypothesis, we will carry out high-precision astrometry of 5 long-duration events, using the ACS/HRC camera. The expected astrometric signal from a BH lens is >1.4 mas, at least 7 times the demonstrated astrometric precision attainable with the HRC. This proposal will thus potentially lead to the first unambiguous detection of isolated stellar-mass BHs, and the first direct mass measurement for isolated stellar-mass BHs through any technique. Detection of several BHs will provide information on the frequency of BHs in the Galaxy, with implications for the slope of the IMF at high masses, the minimum mass of progenitors that produce BHs, and constraints on theoretical models of BH formation. We will select long-duration events which do not show any light contribution from the lens. In addition, the events should have reasonably high amplifications which will ensure that the centroid shift is close to zero at the peak amplification, and will facilitate detection of the parallax signal and hence the distance estimate for the lens. It is easy to identify long-duration events and to determine their time of peak amplification well before the actual peak. Our group includes members of the microlensing survey teams who have access to the survey data for proper selection of such events. To guard against the possibility that the geometric distortion may be dependeant on the location on the detector; we will position the target at different locations along close-to-central-x-axis of the of the detector. We will take most images in a single filter, but also take a small number of images in a different filter to check the color dependenacy, if any, of the astrometric shift. We will try to take as many images as possible in a single ORIENT for better astrometri accuracy. However, maintaining a single ORIENT may not be possible for all the observations. Since almost all of our targets are close to the ecliptic, we plan to use the same orient for nearly half of the year, and then flip it by 180 deg. HOT STARS 12 false 0.0 0.0 false false false false SUPPORTED STAR BULGE GRAVITATIONAL LENS J2000 J2000 EXT-STAR G V-IV J2000 STAR GRAVITATIONAL LENS J2000 J2000 STAR GRAVITATIONAL LENS J2000 ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F555W The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 1320057379000 98.8158702984997 (Tic-Visit :proposal-id 12670 :visit-id "01" :proposal-version -1 :trans-version "20110509" :date "18-Oct-2011 14:29:39.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 774256 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2917 :al-overhead-at-end 167 :internal-dur-at-end 269 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 19.3. 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CASM was run in Phase II mode. 1320025193000 96.47845305547821 (Tic-Visit :proposal-id 12670 :visit-id "06" :proposal-version -1 :trans-version "20110509" :date "18-Oct-2011 17:32:08.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 492704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2779 :al-overhead-at-end 165 :internal-dur-at-end 577 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 1320033758000 96.04857978508647 (Tic-Visit :proposal-id 12670 :visit-id "04" :proposal-version -1 :trans-version "20110509" :date "18-Oct-2011 18:42:42.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 492704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2779 :al-overhead-at-end 165 :internal-dur-at-end 577 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 20.0. CASM was run in Phase II mode. 1334162475633 1335271111000 275.9894739686599 (Tic-Visit :proposal-id 12670 :visit-id "05" :proposal-version -1 :trans-version "20120125" :date "11-Apr-2012 18:41:15.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 492704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2899 :al-overhead-at-end 165 :internal-dur-at-end 575 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 20.0. CASM was run in Phase II mode. 1335368385143 1336352101000 278.14213952230614 (Tic-Visit :proposal-id 12670 :visit-id "06" :proposal-version -1 :trans-version "20120125" :date "25-Apr-2012 17:39:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 633488 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2843 :al-overhead-at-end 167 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 1344349844563 /private/var/folders/vq/vqHvVK0yGlWAHXOSHPkI9U++4D2/-Tmp-/OPVisit3060737386587403673.xml (Tic-Visit :proposal-id 12670 :visit-id "07" :proposal-version -1 :trans-version "20120712" :date "07-Aug-2012 16:30:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 492704 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12670 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12670 :visit-id "07" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2783 :al-overhead-at-end 167 :internal-dur-at-end 575 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3253 :pcs-gap 0 ) true 1 0