18237( 3) - 30-Apr-2026 10:57:45 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18237 Version: 3 Check-in Time: 30-Apr-2026 10:57:45 STScI Edit Number: 1 Title Late-time spectral energy distribution of the first off-nuclear tidal disruption event AT 2024tvd ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Kishore C. Patra University of California - Santa Cruz Y CoI: Dr. Samaporn Tinyanont National Astronomical Research Institute N of Thailand CoI: Nicholas Earl University of Illinois at Urbana - N Champaign CoI: Prof. Ryan Foley University of California - Santa Cruz N 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 Universities Space Research Association 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 flares produced when a star is torn apart and accreted by a massive black hole (MBH). More than 100 TDEs have been discovered so far, almost all originating from galactic nuclei where MBHs typically reside. However, galaxy-merger simulations predict a substantial population of wandering MBHs outside galactic centers--yet no TDE had ever been associated with one until now. The discovery of AT 2024tvd, the first confirmed off-nuclear TDE, opens an entirely new window on this phenomenon. Its location, offset from the bright stellar background of the galactic nucleus, offers a uniquely clean view of accretion physics in action and a chance to test the long-standing idea that TDEs arise from stars bound in nuclear star clusters (NSCs). We propose coordinated multiwavelength observations with JWST (infrared; NIRSpec IFU + NIRCam), HST (UV + optical imaging), and XMM-Newton (X-ray) to obtain a late-time (>700 days after optical peak) spectral energy distribution (SED) spanning X-ray to infrared wavelengths. The SED will be modeled with three components--the accretion disk, an NSC, and a dust echo--to constrain the MBH mass, accretion rate, and disk size. The NSC component will directly test the presence of a bound stellar cluster and measure its mass, age, and metallicity, testing whether the wandering MBH was delivered through a past galaxy merger. The dust component will characterize the temperature and luminosity of the surrounding dust. These observations will provide unique insights into the progression of accretion in TDEs, in addition to the demographics and growth pathways of wandering MBHs. ------------------------------------------------------------------------------------ 18237( 3) - 30-Apr-2026 10:57:45 - [ 2] Observations Description ------------------------ One orbit will be used for ACS/SBC imaging in F140LP and F165LP (for red-leak correction). Two orbits for WFC3 imaging in F225W, F336W, F621M, and F775W. ------------------------------------------------------------------------------------ 18237( 3) - 30-Apr-2026 10:57:45 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 2024TVD UNIDENTIFIED, ACCRETION RA=17H10M42.5700S +/- 0.1", J2000 Z = V = 22 DISK, INFRARED EMITTER, DEC=+28D50'14.99" +/- 0.1" 0.045 OPTICAL EMITTER, ULTRAVIOLET EMITTER, X-RAY EMITTER Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 18237( 3) - 30-Apr-2026 10:57:45 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-SBC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.179 Line_Spacing 0.116 Coordinate_Frame POS-TARG Pattern_Orient 20.02 Angle_Between_Sides 63.65 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18237( 3) - 30-Apr-2026 10:57:45 - [ 5] Visit: 01 (ACS-SBC visit) Visit Requirements: GROUP 01, 02 WITHIN 30D On Hold Comments: Additional Comments: Far-UV observation of 2024tvd 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 2024TVD ACS/SBC ACCUM SBC F140LP 1 200 S GS ACQ SCENARIO BASE1OR; see below PATTERN 1 1-2 (992 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 2024TVD ACS/SBC ACCUM SBC F165LP 1 200 S see below (992 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2024TVD 1 ACS/SBC ACCUM SBC F140LP 1 none none none 1 248.0 S 2024TVD 1 ACS/SBC ACCUM SBC F140LP 2 none none none 1 248.0 S 2024TVD 1 ACS/SBC ACCUM SBC F140LP 3 none none none 1 248.0 S 2024TVD 1 ACS/SBC ACCUM SBC F140LP 4 none none none 1 248.0 S 2024TVD 2 ACS/SBC ACCUM SBC F165LP 1 none none none 1 248.0 S 2024TVD 2 ACS/SBC ACCUM SBC F165LP 2 none none none 1 248.0 S 2024TVD 2 ACS/SBC ACCUM SBC F165LP 3 none none none 1 248.0 S 2024TVD 2 ACS/SBC ACCUM SBC F165LP 4 none none none 1 248.0 S 18237( 3) - 30-Apr-2026 10:57:45 - [ 6] Visit: 02 (WFC3 visit) Visit Requirements: On Hold Comments: Additional Comments: Near-UV and optical observations of 2024tvd 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 2024TVD WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=16 1 300 S GS ACQ SCENARIO BASE1OR; S 1C-SUB see below PATTERN 2 1-4 (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 2024TVD WFC3/UVI ACCUM UVIS2-C1K F621M FLASH=12 1 300 S S 1C-SUB see below (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 2024TVD WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=15 1 300 S S 1C-SUB see below (1005 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 2024TVD WFC3/UVI ACCUM UVIS2-C1K F775W FLASH=10 1 300 S S 1C-SUB see below (1005 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2024TVD 1 WFC3/UVI ACCUM UVIS2-C1 F225W 1 none none none 1 335.0 S S K1C-SUB 2024TVD 1 WFC3/UVI ACCUM UVIS2-C1 F225W 2 none none none 1 335.0 S S K1C-SUB 2024TVD 1 WFC3/UVI ACCUM UVIS2-C1 F225W 3 none none none 2 335.0 S S K1C-SUB 2024TVD 2 WFC3/UVI ACCUM UVIS2-C1 F621M 1 none none none 1 335.0 S S K1C-SUB 2024TVD 2 WFC3/UVI ACCUM UVIS2-C1 F621M 2 none none none 1 335.0 S S K1C-SUB 2024TVD 2 WFC3/UVI ACCUM UVIS2-C1 F621M 3 none none none 2 335.0 S S K1C-SUB 2024TVD 3 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 335.0 S S K1C-SUB 2024TVD 3 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 2 335.0 S S K1C-SUB 2024TVD 3 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none none none 2 335.0 S S K1C-SUB 2024TVD 4 WFC3/UVI ACCUM UVIS2-C1 F775W 1 none none none 1 335.0 S S K1C-SUB 18237( 3) - 30-Apr-2026 10:57:45 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2024TVD 4 WFC3/UVI ACCUM UVIS2-C1 F775W 2 none none none 2 335.0 S S K1C-SUB 2024TVD 4 WFC3/UVI ACCUM UVIS2-C1 F775W 3 none none none 2 335.0 S S K1C-SUB 18237( 3) - 30-Apr-2026 10:57:45 - [ 8] Summary Form for Proposal 18237 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures SBC, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/SBC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=10, FLASH=12, FLASH=15, FLASH=16 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 01, 02 WITHIN 30D, GS ACQ SCENARIO BASE1OR, PATTERN 1 1-2, PATTERN 2 1-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F140LP, F165LP, F225W, F336W, F621M, F775W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2024TVD ------------------------------------------------------------------------------------------------------------------------------------