18054( 5) - 02-Oct-2025 12:46:05 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18054 Version: 5 Check-in Time: 02-Oct-2025 12:46:05 STScI Edit Number: 1 Title Are 3XMM J2150 and EP240222a really off-nuclear tidal disruption events? ------------------------------------------------------------------------------------ Type Cycle GO 33 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Kishore C. Patra University of California - Santa Cruz Y CoI: Prof. Ryan Foley University of California - Santa Cruz Y ------------------------------------------------------------------------------------ Abstract Galaxy merger simulations predict a substantial population of off-nuclear massive black holes (MBHs). Tidal disruption events (TDEs) occurring around these wandering MBHs provide a rare window into studying these otherwise dormant black holes. Recently, AT 2024tvd was confirmed as the first optically selected off-nuclear TDE. Two other X-ray selected events have also been put forward as off-nuclear TDE candidates: 3XMM J2150 and EP240222a. However, their separation from the purported host galaxy is large (13 and 35 kpc, respectively). It is not clear that the two MBHs are even linked to the larger "host galaxy". Therefore, we request deep HST imaging of these 2 off-nuclear TDE candidates to 1) detect signatures of faint satellite galaxies that might host these TDEs, ii) detect UV emission from the TDe accretion disks. These deep and high spatial resolution images will help answer whether these are indeed off-nuclear MBHs like AT 2024tvd. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain imaging with WFC3/UVIS of 2 off-nuclear tidal disruption event candidates: Visit 1) 3XMMJ215: F225W (1 orbit) Visit 2) EP240222A: F225W (1 orbit) + F625W (1 orbit) ------------------------------------------------------------------------------------ 18054( 5) - 02-Oct-2025 12:46:05 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 3XMMJ215 GALAXY, ACCRETION DISK, RA=21H50M22.4000S, J2000 Z = V = 23 ELLIPTICAL, TIDAL TAIL DEC=-05D51'8.00" 0.055 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 ------------------------------------------------------------------------------------------------------------------------------------ 2 EP240222A GALAXY, ACCRETION DISK, RA=11H32M4.3204S, J2000 Z = V = 24 ELLIPTICAL, TIDAL TAIL DEC=+27D00'17.60" 0.03275 Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 18054( 5) - 02-Oct-2025 12:46:05 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 18054( 5) - 02-Oct-2025 12:46:05 - [ 4] Visit: 01 (3XMMJ215) 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 3XMMJ215 WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=21 1 500 S GS ACQ SCENARIO ONEB1OR; S 1C-CTE see below PATTERN 1 1 (2172 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 | ------------------------------------------------------------------------------------------------------------------------------------ 3XMMJ215 1 WFC3/UVI ACCUM UVIS2-C1 F225W 1 none none none 1 543.0 S S K1C-CTE 3XMMJ215 1 WFC3/UVI ACCUM UVIS2-C1 F225W 2 none none none 1 543.0 S S K1C-CTE 3XMMJ215 1 WFC3/UVI ACCUM UVIS2-C1 F225W 3 none none none 1 543.0 S S K1C-CTE 3XMMJ215 1 WFC3/UVI ACCUM UVIS2-C1 F225W 4 none none none 1 543.0 S S K1C-CTE 18054( 5) - 02-Oct-2025 12:46:05 - [ 5] Visit: 02 (EP240222A) 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 EP240222A WFC3/UVI ACCUM UVIS1 F225W FLASH=21 1 500 S GS ACQ SCENARIO ONEB1OR; S see below PATTERN 1 1-2 (2098 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 EP240222A WFC3/UVI ACCUM UVIS1 F625W FLASH=8 1 500 S S see below (2098 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 | ------------------------------------------------------------------------------------------------------------------------------------ EP240222A 1 WFC3/UVI ACCUM UVIS1 F225W 1 none none none 1 527.0 S S EP240222A 1 WFC3/UVI ACCUM UVIS1 F225W 2 none none none 1 527.0 S S EP240222A 1 WFC3/UVI ACCUM UVIS1 F225W 3 none none none 2 522.0 S S EP240222A 1 WFC3/UVI ACCUM UVIS1 F225W 4 none none none 2 522.0 S S EP240222A 2 WFC3/UVI ACCUM UVIS1 F625W 1 none none none 1 527.0 S S EP240222A 2 WFC3/UVI ACCUM UVIS1 F625W 2 none none none 1 527.0 S S EP240222A 2 WFC3/UVI ACCUM UVIS1 F625W 3 none none none 2 522.0 S S EP240222A 2 WFC3/UVI ACCUM UVIS1 F625W 4 none none none 2 522.0 S S 18054( 5) - 02-Oct-2025 12:46:05 - [ 6] Summary Form for Proposal 18054 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS1, UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=21, FLASH=8 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO ONEB1OR, PATTERN 1 1, PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F225W, F625W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3XMMJ215, EP240222A ------------------------------------------------------------------------------------------------------------------------------------