0 Assigned ID: 6525 ----- Attempting Submission 1 (Thu Apr 10 16:45:29 GMT 2025) ----- ----- Attempting Submission 2 (Tue Apr 15 19:05:27 GMT 2025) ----- 0 ----- Attempting Submission 1 (Mon Aug 11 16:53:07 GMT 2025) ----- Using 35 year old tidal disruption events to test the fundamentals of accretion disk theory Tidal Disruption Events (TDEs) occur when stars pass too close to supermassive black holes and are torn apart by tidal forces and subsequently accreted. The oldest known TDE candidates are six sources discovered by the ROSAT X-ray satellite in the 1990's, which showed soft X-ray flares which decayed to unobservable X-ray flux levels over $\sim 5-10$ years. In the following 20 years our theoretical and observational understanding of TDEs has strengthened, and a substantial breakthrough has occurred: while significant uncertainties remain in the origin of the UV/optical light emitted during the initial flare, late-time optical/UV emission is known to originate from accretion disks in these events, and to last for at least $\gtrsim 2000$ days. This means, despite their X-ray emission having faded decades ago, all six ROSAT TDEs should be bright and detectable in the UV today, over 30 years after disruption. The detection with HST of bright UV emission from these six events would allow six black hole mass measurements to be performed, but the detection or non-detection of each of these systems will teach the disk theory community a great deal about black hole accretion disk stability at low luminosities, something which is observationally inaccessible to any other known massive black hole disk systems. The proposal aims to observe decade-old (1990s) tidal disruption events (TDEs) using multi-band UV/optical imaging. We will observe each of the 6 TDEs in 3 filters for 2 orbits each. The first orbit will be in F225W, and the second orbit will be split between F438W and F625W. Dr. Andy Mummery is an experienced theoretical astrophysicist who developed the accretion disk framework which will be used in interpreting these results. He will lead the analysis of this project. Dr. Suvi Gezari is the Project Scientist for Multi-Messenger Astrophysics and Time Domain Astronomy at the Space Telescope Science Institute, and is a world leader in the discovery and characterization of TDEs. Muryel Guolo is a graduate student at Johns Hopkins University. He is experienced in the reduction and analysis of X-ray and UV data from several missions, including HST. Supermassive Black Holes and Active Galaxies 6 false false false false false false SUPPORTED GALAXY ACCRETION DISK This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. J2000 J2000 GALAXY ACCRETION DISK J2000 J2000 GALAXY ACCRETION DISK J2000 J2000 GALAXY ACCRETION DISK J2000 J2000 GALAXY ACCRETION DISK J2000 J2000 GALAXY ACCRETION DISK J2000 J2000 WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F625W POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1 false POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 2 false The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:10:30.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2664 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3044 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2662 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3044 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:22:01.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2592 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "02" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2594 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2974 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "03" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:32:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2772 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3152 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "03" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2770 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3152 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "04" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:35:16.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2664 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3044 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "04" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2662 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3044 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "05" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:39:08.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "05" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2604 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "05" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2606 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18081 :visit-id "06" :proposal-version -1 :trans-version "20250624" :date "11-Aug-2025 11:39:01.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2310000 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18081 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18081 :visit-id "06" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2628 :al-overhead-at-end 125 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3011 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18081 :visit-id "06" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2630 :al-overhead-at-end 121 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3011 :pcs-gap 0 ) true 2 0