We have not selected CVZ as an option since it imposes tight constraints on the schedulability. If possible, CVZ scheduling is desired because it will provide more individual frames, thus improving our S/N. However, the 8 requested orbits do not consider CVZ, so if iit s not granted it will not affect the mentioned calculations. -1436987615 Assigned ID: 2336 ----- Attempting Submission 1 (Fri Apr 09 22:08:23 GMT 2021) ----- We have shifted the pointing because of detector safety reasons, i.e. due to the presence of some bright stars in FUV. We used UVIT-FUV images to determine the best position that avoids 2 bright FUV sources. FUV sources inside the FOV have been determined to be safe for observation according to DS9-photometric analysis on UVIT images. Angles have been chosen according to the Aladin configuration shown on APT. The angles have been constrained to avoid other bright stars within the safety circle and to avoid the detector gap, however, there are many scheduling opportunities. FUV Images have been sent to our program scientist, who also added that there is NO re-review needed by him for our ORIENT updates. Giving the cooling that the detector needs to obtain optimal images, scheduling visits contiguously is not suggested. However, we strongly suggest to schedule at least 2 visits within the same day and/or consecutive days after the first observation. This is to optimize the search for coherent periodicity in the binary AM1, which is the aim of the program. This is especially important given that during phase 2 a few less exposures could be accomodated per orbit. If possible to schedule the observations in the CVZ that would further benefit the program. -846463326 ----- Attempting Submission 1 (Wed Jul 28 18:50:07 GMT 2021) ----- ----- Attempting Submission 2 (Fri Oct 22 22:48:44 GMT 2021) ----- ----- Attempting Submission 3 (Thu Nov 04 22:39:52 GMT 2021) ----- Confirming the first outbursting AM CVn in a globular cluster AM CVns are double white dwarf binaries with orbital periods ~5-65 mins. They have been predicted to exist in large amounts in globular clusters due to stellar interactions, but while binaries harboring neutron stars and even black holes have been previously identified, no single AM CVn has ever been confirmed to reside in any Galactic globular cluster. We propose to use 8 HST orbits to obtain FUV photometry and determine the sub-hour orbital period of a recently detected, He-rich, accreting binary in the globular cluster 47 Tuc. The system has multiwavelength characteristics that match well those expected for AM CVns. The confirmation of a sub-hour period, as expected for AM CVns, has profound implications for the dynamical evolution of globular clusters and whether they might be factories of SN Ia and ultracompact binaries that emit gravitational waves. For this program we are using imaging with ACS/SBC in the FUV filter F140LP to look for periodicities. We are pointing the center of the detector towards a region shifted from AM1 (the target of interest) for 2 reasons: 1) reduce the effects of dark currents in the FUV, which are worst at the center of the detector, 2) maximize the usage of HST by obtaining infomation of many other stars in the cluster that harbor stellar remnants. Note that AM1 is always within the FOV. We are considering only 2 orbits per visit to reduce the effects of temperature and dark currents on the detector. Giving the cooling that the detector needs to obtain optimal images, scheduling visits contiguously is not suggested. However, we suggest to schedule at least 2 visits within the same day and/or consecutive days after the first observation. This is to optimize the search for coherent periodicity in the binary AM1, which is the aim of the program. If possible to schedule the observations in the CVZ that would further benefit the program. We are not considering acquisition images previous to the science images, because we were informed that ACS/SBC does not require those. The team members of this proposal are experts on the study of compact binaries in globular clusters (GCs). They have made important contributions to the field using data taken at different wavelengths. All of them have several published papers on compact binaries in GCs, including several papers based on HST data. Dr. L.E. Rivera Sandoval has expertise reducing and analyzing UV HST data. She has carried out NUV tudies of compact binaries in 47 Tuc, leading to the discovery of the first AM CVn candidate in that cluster as well as doubled the number of cataclysmic variables known there. She is the PI of 3 HST proposals. Prof. T. J. Maccarone has expertise in X-ray observations for understanding the populations of X-ray binaries in the field and in star clusters, and in correlating X-ray source properties with multiwavelength properties. Prof. C. O. Heinke is an expert on X-ray observations of GCs. He has also been PI and Co-I of several succesful HST proposals. Prof. C. Knigge is an expert on cataclysmic variable stars and was involved in several further HST observing campaigns of GCs (e.g. M80 - GO-10183, M15 - GO-9792, 47 Tuc - GO-8219). Dr. D. R. Zurek is an expert in the reduction of data taken with all HST instruments. He has expertise on imaging and spectroscopy, and has been involved in various HST observing campaigns, both as a PI and Co-I. He has led the far-UV observations on the GC NGC 1851 (GO-10184 and GO-13394), where he identified the first AM CVn candidate in a GC. Prof. L. Althaus is an expert on WD evolutionary models. He has produced many cooling tracks for WDs with different compositions, masses and temperatures. Stellar Physics and Stellar Types Stellar Populations and the Interstellar Medium 6 false false true false false false false false SUPPORTED STELLAR CLUSTER ACCRETION DISK GLOBULAR CLUSTER NO pointing falls in a white part of the image, so the magnitude provided here is just to avoid a system error. J2000 J2000 ACS/SBC Imaging No No F140LP /private/var/folders/4z/t_bqgcq137j8sd4xmqs9vq0w0000gn/T/OPVisit20486947661358833.xml The scheduling data was generated by CASM 29.2. CASM was run in Phase II mode. 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CASM was run in Phase II mode. 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CASM was run in Phase II mode. (Tic-Visit :proposal-id 16694 :visit-id "03" :proposal-version -1 :trans-version "20210514" :date "04-Nov-2021 16:55:45.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 703568 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16694 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16694 :visit-id "03" :orbit-number 1 :pcs-time 383 :si-vis-utilization 3142 :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 3525 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16694 :visit-id "03" :orbit-number 2 :pcs-time 392 :si-vis-utilization 3133 :al-overhead-at-end 0 :internal-dur-at-end 320 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3525 :pcs-gap 0 ) true 2 0 /private/var/folders/4z/t_bqgcq137j8sd4xmqs9vq0w0000gn/T/OPVisit2804412515959579598.xml The scheduling data was generated by CASM 29.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 16694 :visit-id "04" :proposal-version -1 :trans-version "20210514" :date "04-Nov-2021 16:57:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "28" :si-bright-earth-limb-angle 20.0 :data-volume 703568 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16694 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16694 :visit-id "04" :orbit-number 1 :pcs-time 383 :si-vis-utilization 3142 :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 3525 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16694 :visit-id "04" :orbit-number 2 :pcs-time 392 :si-vis-utilization 3133 :al-overhead-at-end 0 :internal-dur-at-end 320 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3525 :pcs-gap 0 ) true 2 0