0 Assigned ID: 5282 ----- Attempting Submission 1 (Tue Mar 26 00:42:15 GMT 2024) ----- HST Phase I Proposal 5282 successfully submitted. Receipt: # 5282-1 ----- Attempting Submission 2 (Tue Mar 26 17:15:19 GMT 2024) ----- FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser FLASH level may be too high for this exposure or a long subexposure. See extended explanation in the diagnostic browser Resubmission 5: changing the exposure time for Visit 10 from 140 --> 120 sec, based on source being brighter in Visit 06 than Visits 01-05. ==================================================================================================== Resubmission 5: changing the exposure time for Visit 08 and 09 from 140 --> 120 sec, based on source being brighter in Visit 06 than Visits 01-05. ==================================================================================================== Resubmission 4: changing the exposure time for Visit 07 from 140 --> 120 sec, based on source being brighter in Visit 06 than Visits 01-05. ==================================================================================================== Resubmission 3: changing the exposure times for Visit 03 through 10 from 120 sec --> 140 sec, based on 2st epoch of data. ==================================================================================================== Resubmission 2: changing the exposure times for Visit 02 from 120 sec --> 140 sec, based on 1st epoch of data. ==================================================================================================== Resubmission: fixing the visit windows. ==================================================================================================== 1. Regarding "Warning (Form) FLASH level may be too high for this exposure or a long subexposure.": We have two targets, one bright (F606W = 17.57) and one faint (F606W = 20.17) of which we are trying to obtain astrometric precision of 0.1 - 0.2 mas. We set the FLASH to the maximum of 40e- because we care more about the correct shape of stars for optimal ePSF fitting rather than extra noise in the image. The high FLASH is particularly important for the fainter target. 2. The exposure times we chose are conservative, as these targets have not been observed in this particular configuration before (WFC3-UVIS, F606W filter). We anticipate increasing the exposure times after the first visit, when we know exactly how bright our targets are after the first visit. 445474383 ----- Attempting Submission 1 (Thu Aug 08 16:50:18 GMT 2024) ----- ----- Attempting Submission 2 (Thu Sep 19 17:08:11 GMT 2024) ----- ----- Attempting Submission 3 (Fri Nov 22 23:05:53 GMT 2024) ----- ----- Attempting Submission 4 (Tue Dec 17 18:21:50 GMT 2024) ----- ----- Attempting Submission 5 (Fri Jun 13 23:34:13 GMT 2025) ----- ----- Attempting Submission 6 (Mon Jul 21 19:15:51 GMT 2025) ----- HST Phase II Proposal 17820 successfully submitted. Receipt: # 17820-6 ----- Attempting Submission 7 (Mon Jul 21 20:19:31 GMT 2025) ----- Regarding "Warning (Form) FLASH level may be too high for this exposure or a long subexposure.": We have two targets, one bright (F606W = 17.57) and one faint (F606W = 20.17) of which we are trying to obtain astrometric precision of 0.1 - 0.2 mas. We set the FLASH to the maximum of 40e- because we care more about the correct shape of stars for optimal ePSF fitting rather than extra noise in the image. The high FLASH is particularly important for the fainter target. First mass measurement of black holes in a globular cluster We propose to perform astrometric follow-up of two black hole candidates in the Galactic globular cluster NGC 3201. Globular clusters are dense and dynamic stellar systems that are expected to harbor populations of stellar mass black holes. These black holes play an important role in the evolution of the cluster, as well as sourcing a variety of high-energy phenomena, such as binary black hole mergers. Two black hole candidates were identified through a radial velocity survey of the nearby globular cluster NGC 3201. However, because of a degeneracy between the orbital inclination and mass, only a lower limit on the black hole candidate masses can be derived from the existing radial velocities. In contrast, an astrometric orbit can break this degeneracy and enable a direct mass measurement of these black holes. We propose to use HST WFC3-UVIS imaging to obtain 10 measurements with an astrometric precision of 0.1 - 0.2 mas in order to map out the orbits of the two black hole candidates, measure their orbital inclinations, and most importantly, their masses. This will lead to the first mass measurement of black holes in a globular cluster, which will enable comparisons to the properties of black holes in field environments, insight into gravitational wave sources, and the dynamical evolution of globular clusters. We will obtain 10 epochs of WFC3-UVIS imaging of NGC 3201 BH1 and BH2 in order to measure their orbital motions and their masses. We will use the F606W filter and the UVIS2-2K2C-SUB subarray. For the observations, we wil dither small amounts (approximately 10 pixels) to sample the pixel phase, mitigate the effect of bad pixels, and maximize the SNR without saturating our brighter target (F606W = 17.57). Co-PI Casey Lam is a Carnegie Fellow at Carnegie Observatories. She is an an expert in astrometric microlensing, and led the discovery of the first isolated stellar-mass black hole performed using astrometric measurements from HST WFC3-UVIS imaging. Co-PI Kyle Kremer is a NASA Einstein Fellow at Caltech. He is an expert in N-body simulations of dense star clusters and compact objects. In particular, he has conducted extensive theoretical work on the role of black holes in the dynamics and evolution of globular clusters. Co-I Andrea Bellini is a Principal Staff Scientist at Space Telescope Science Institute. He is an expert in high-precision astrometry and photometry with HST, and has led many projects measuring proper motions of stars in globular clusters. In addition, he has made significant contributions to the software and solutions needed to perform these analyses, such as geometric distortion corrections and empirical PSF models. Co-I Mattia Libralato is an IAF Fellow at the Istituto Nazionale Di Astrofisica - Osservatorio Astronomico di Padova. He is also an expert in high-precision astrometry and photometry with HST, and has led many projects measuring proper motions of stars in globular clusters. In particular he has led the analysis of the archival NGC 3201 astrometry. Co-I Kareem El-Badry is an Assistant Professor of Astronomy at Caltech. He is an expert in binary stars and stellar-mass black holes. He led the discovery and confirmation of the first two black holes found by Gaia. Stellar Physics and Stellar Types 6 false false false false false false SUPPORTED STELLAR CLUSTER GLOBULAR CLUSTER J2000 J2000 WFC3/UVIS Imaging No No F606W POS-TARG DITHER 0.38 LINE false false 8 45 SPIRAL 1 false The scheduling data was generated by CASM 33.1. 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