Multiwavelength JWST and HST observations of the off-nuclear TDE AT 2025abcr

This is HST Phase I submission for the accepted joint JWST+HST DD proposal 12485 -1494632470 Assigned ID: 6938 ----- Attempting Submission 1 (Wed Nov 26 10:05:42 GMT 2025) ----- HST Phase I Proposal 6938 successfully submitted. Receipt: # 6938-1 This target is not used in this proposal. V2: updated exposure time for offset star -1418281753 ----- Attempting Submission 1 (Fri Nov 28 09:25:27 GMT 2025) ----- HST Phase II Proposal 18220 successfully submitted. Receipt: # 18220-1 ----- Attempting Submission 2 (Fri Nov 28 12:12:57 GMT 2025) ----- Optional offset star to consider for target acquistion Multiwavelength JWST and HST observations of the off-nuclear TDE AT 2025abcr Tidal disruption events (TDEs) are luminous, multiwavelength flares that occur when a star is torn apart by a massive black hole (MBH). Most TDEs originate in galactic nuclei, where MBHs typically reside, but galaxy-merger simulations predict a substantial population of off-nuclear, wandering MBHs. AT 2025abcr is only the second optically selected off-nuclear TDE, and initial estimates suggest it may be powered by an intermediate-mass black hole (IMBH). We propose multiwavelength JWST+HST Director's Discretionary observations using JWST NIRSpec IFU and MIRI LRS, alongsideHST STIS UV spectroscopy and WFC3 imaging, with three primary science goals: (1) robustly measure the BH mass and test for the presence of a nuclear star cluster (NSC) around the wandering BH; (2) probe early-time accretion physics and outflows via UV spectroscopy; and (3) use spatially resolved stellar kinematics to determine the origin of the off-nuclear BH. These observations will address fundamental questions about the demographics of wandering BHs (including IMBHs) the origin of offset MBHs, and the evolutionary fate of their accompanying NSCs. We will use 3 orbits for STIS FUV and NUV MAMA spectroscopy with the following set up: 1) 2 orbits for STIS/FUV-MAMA, TIME-TAG, 52x0.2" slit, G140L 2) 1 orbit for STIS/NUV-MAMA, TIME-TAG, 52x0.2" slit, G230L Target Acquisition will be done with an offset star. We will use 1 orbit for WFC3/UVIS imaging in F336W, F621M, F775W. This team has performed extensive observational and theoretical work in the area of black hole and stellar astrophysics, especially TDEs, AGN physics, and supernovae. PI Dr. Kishore Patra is an expert observer who has extensive experience in time-domain astronomy. He has lead several HST/JWST programs as a PI and has authored several papers on supernovae, TDEs and related nuclear transient events. He will lead the data analysis and timely publication of results. CoI Prof. Ryan Foley is an expert observer and previous PI/CoI of multiple HST and JWST programs. He is a coauthor on several TDE papers. CoIs Prof. Ashley Villar, Prof. Sebastian Gomez, and Prof. Decker French are experts on theory and multi-wavelength observations of extragalactic transients, including TDEs, core-collapse supernovae, and kilonovae. They are also experts in X-ray, UV, optical and IR astronomy. CoIs Dr. Kirsty Taggart and Dr. Prasiddha Arunachalam are postdocs and expert observers with extensive experience with transients and JWST data. They have also led successful JWST and HST programs. CoIs Dr. Phillip Macias and Prof. Enrico Ramirez-Ruiz are theoretical astrophysicists focusing on high-energy phenomena. CoI Dr. Samaporn Tinyanont is an expert on infrared astronomy. CoIs Kyle Davis, Ravjit Kaur, and Nicholas Earl are graduate students. They are observers with expertise in multi-wavelength, time-domain astronomy. All CoIs will assist PI Patra with data analysis and timely publication of results. Supermassive Black Holes and Active Galaxies Stellar Populations and the Interstellar Medium 0 false SUPPORTED UNIDENTIFIED ACCRETION DISK INFRARED EMITTER OPTICAL EMITTER ULTRAVIOLET EMITTER X-RAY EMITTER NO J2000 J2000 UV flux expected to be 19 +/- 0.4 AB mag STAR M III-I NO Offset star 1 for TA GAIA-DR3-2452799545790172672 J2000 STAR F0-F2 M III-I NO Offset star 2 for TA GAIA-DR3-2452799545790205312 J2000 The scheduling data was generated by CASM 33.1. CASM was run in Phase I mode. STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 The scheduling data was generated by CASM 33.1. CASM was run in Phase I mode. WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F621M WFC3/UVIS Imaging No No F775W POS-TARG DITHER 0.145 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE 1

false

1764330685376 /private/var/folders/4m/9jswqm216v34lr2yv9yv43340000gn/T/OPVisit15209103664995877142.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18220 :visit-id "01" :proposal-version -1 :trans-version "20250929" :date "28-Nov-2025 03:51:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 1252880 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18220 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18220 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 0 :internal-dur-at-end 178 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18220 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 0 :internal-dur-at-end 2299 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18220 :visit-id "01" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 0 :internal-dur-at-end 582 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) true 3 0 This is an offset star for target acquistion 1764330714811 /private/var/folders/4m/9jswqm216v34lr2yv9yv43340000gn/T/OPVisit6177729691512228150.xml The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 18220 :visit-id "02" :proposal-version -1 :trans-version "20250929" :date "28-Nov-2025 03:51:54.0" :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 160432 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18220 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18220 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2596 :al-overhead-at-end 84 :internal-dur-at-end 212 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2976 :pcs-gap 0 ) true 1 0