18220( 3) - 28-Nov-2025 12:31:35 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18220 Version: 3 Check-in Time: 28-Nov-2025 12:31:35 STScI Edit Number: 0 Title Multiwavelength JWST and HST observations of the off-nuclear TDE AT 2025abcr ------------------------------------------------------------------------------------ Type Cycle GO/DD 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Kishore C. Patra University of California - Santa Cruz Y CoI: Nicholas Earl University of Illinois at Urbana - N Champaign CoI: Prof. Ryan Foley University of California - Santa Cruz N CoI: Dr. Samaporn Tinyanont National Astronomical Research Institute N of Thailand CoI: Kyle Davis University of California - Santa Cruz N CoI: Dr. Enrico Ramirez-Ruiz University of California - Santa Cruz N CoI: Prof. Ashley Villar Harvard University N CoI: Dr. Sebastian Gomez University of Texas at Austin N CoI: Dr. K. Decker French University of Illinois at Urbana - N Champaign CoI: Dr. Kirsty Taggart University of California - Santa Cruz N CoI: Prasiddha Arunachalam University of California - Santa Cruz N CoI: Dr. Phillip Macias University of California - Santa Cruz N CoI: Ravjit Kaur University of California - Santa Cruz N ------------------------------------------------------------------------------------ Abstract 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. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will use 3 orbits for STIS FUV and NUV MAMA spectroscopy with the following set up: 18220( 3) - 28-Nov-2025 12:31:35 - [ 2] 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. ------------------------------------------------------------------------------------ 18220( 3) - 28-Nov-2025 12:31:35 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 2025ABCR UNIDENTIFIED, ACCRETION RA=01H46M55.3860S +/- 0.1", J2000 Z = 0.05 V = 19.5 +/- 0.4 UV flux expected to be DISK, INFRARED EMITTER, DEC=-15D22'15.60" +/- 0.1" 19 +/- 0.4 AB mag OPTICAL EMITTER, ULTRAVIOLET EMITTER, X-RAY EMITTER Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 2025ABCR-OFF STAR, M III-I RA=01H46M54.2745S, J2000 V = 16.5 +/- 0.05 SET-STAR1 DEC=-15D22'14.50" Reference Frame: ICRS Extended: NO Comments: Offset star 1 for TA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016 1.8890353759132948E-4 -0.0750691 0.0033 ------------------------------------------------------------------------------------------------------------------------------------ 3 2025ABCR-OFF STAR, F0-F2, M III-I RA=01H46M55.9573S, J2000 V = 14.83 +/- 0.05 SET-STAR2 DEC=-15D21'31.38" Reference Frame: ICRS Extended: NO Comments: Offset star 2 for TA Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2016 0.0032656201408023406 -0.00676602616 0.0032 ------------------------------------------------------------------------------------------------------------------------------------ 18220( 3) - 28-Nov-2025 12:31:35 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18220( 3) - 28-Nov-2025 12:31:35 - [ 5] Visit: 01 (STIS UV Spectroscopy) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2025ABCR-OF STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 5 S (5 S) FSET-STAR1 Comments: This is an offset star for target acquistion ------------------------------------------------------------------------------------------------------------------------------------ 2 2025ABCR STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=500 1 2000 S -MAMA G see below (2049 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2025ABCR STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=500 1 2000 S -MAMA G see below (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2025ABCR STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=500 1 2000 S -MAMA G see below (2568 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2025ABCR-OFFSET-STA 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A R1 2025ABCR 2 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 1 2049.0 S -MAMA G 2025ABCR 3 STIS/FUV TIME-TA 52X0.2 G140L 1425 none none none none 2 2568.0 S -MAMA G 2025ABCR 4 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 3 2568.0 S -MAMA G 18220( 3) - 28-Nov-2025 12:31:35 - [ 6] Visit: 02 (WFC3 Imaging) Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 2025ABCR WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=16 1 180 S PATTERN 1 1-3 S 1C-SUB see below (537 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 2025ABCR WFC3/UVI ACCUM UVIS2-C1K F621M FLASH=15 1 180 S (540 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2025ABCR WFC3/UVI ACCUM UVIS2-C1K F775W FLASH=13 1 180 S (540 S 1C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ 2025ABCR 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 177.0 S S K1C-SUB 2025ABCR 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 1 N/A S K1C-SUB 2025ABCR 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none none none 1 N/A S K1C-SUB 2025ABCR 2 WFC3/UVI ACCUM UVIS2-C1 F621M 1 none none none 1 N/A S K1C-SUB 2025ABCR 2 WFC3/UVI ACCUM UVIS2-C1 F621M 2 none none none 1 N/A S K1C-SUB 2025ABCR 2 WFC3/UVI ACCUM UVIS2-C1 F621M 3 none none none 1 N/A S K1C-SUB 2025ABCR 3 WFC3/UVI ACCUM UVIS2-C1 F775W 1 none none none 1 N/A S K1C-SUB 2025ABCR 3 WFC3/UVI ACCUM UVIS2-C1 F775W 2 none none none 1 N/A S K1C-SUB 2025ABCR 3 WFC3/UVI ACCUM UVIS2-C1 F775W 3 none none none 1 N/A S K1C-SUB 18220( 3) - 28-Nov-2025 12:31:35 - [ 7] Summary Form for Proposal 18220 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=500, FLASH=13, FLASH=15, FLASH=16 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W, F621M, F775W, G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2025ABCR, 2025ABCR-OFFSET-STAR1 ------------------------------------------------------------------------------------------------------------------------------------