JWST and Keck observations of the off-nuclear tidal disruption event TDE 2025abcr: An evolving reprocessing layer
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| Main Authors: | , , , , , , , , , , , , , , , , |
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2026
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| author | Patra, Kishore C. Liepold, Emily R. Earl, Nicholas Foley, Ryan J. Ma, Chung-Pei Gomez, Sebastian Davis, Kyle W. Ramirez-Ruiz, Enrico French, K. Decker Walsh, Jonelle L. Kaur, Ravjit Taggart, Kirsty Candanoza, Joshua Villar, V. Ashley Arunachalam, Prasiddha Macias, Phillip Tinyanont, Samaporn |
| author_facet | Patra, Kishore C. Liepold, Emily R. Earl, Nicholas Foley, Ryan J. Ma, Chung-Pei Gomez, Sebastian Davis, Kyle W. Ramirez-Ruiz, Enrico French, K. Decker Walsh, Jonelle L. Kaur, Ravjit Taggart, Kirsty Candanoza, Joshua Villar, V. Ashley Arunachalam, Prasiddha Macias, Phillip Tinyanont, Samaporn |
| contents | Off-nuclear tidal disruption events (TDEs) provide a rare probe of massive black holes (MBHs) outside galactic nuclei. Only a handful are known, including five X-ray-selected candidates and two optically selected events. We present observations of TDE 2025abcr, the second optically selected off-nuclear TDE, discovered at a projected offset of $9.08 \pm 0.02$ kpc from the nucleus of its host galaxy. We analyze X-ray, UV, optical, and infrared (IR) data from Swift, Keck, ZTF, and JWST. Broad H and He emission lines in the optical and IR confirm a TDE-H-He classification. From luminosity scaling relations and MOSFiT modeling, we infer a BH mass of $10^{6}$-$10^{7}\,M_{\odot}$, substantially smaller than the $10^{8.35 \pm 0.41}\,M_{\odot}$ BH inferred for the host-galaxy nucleus. We observe velocity evolution in the N III + He II emission complex, shifting from $-500$ km s$^{-1}$ at day $-7$ to $+1000$ km s$^{-1}$ by day $+29$, which we interpret as radiative transfer effects in an evolving reprocessing layer. The IR SED deviates from a thermal blackbody, with $νL_ν \propto λ^{-2.13 \pm 0.04}$, significantly shallower than the Rayleigh-Jeans slope of $λ^{-3}$. We rule out dust as the source of this IR excess. Two possibilities remain: free-free emission from reprocessing gas, or an unresolved stellar cluster at the TDE location. Reprocessed emission provides a natural explanation for the IR excess but an underlying stellar cluster of mass $\log(M_{*}/M_{\odot}) = 7.57 \pm 0.02$ and age $<$2 Gyr is also consistent with the data. If interpreted as a stellar cluster, the inferred mass suggests a stripped remnant of a satellite galaxy. The wandering MBH most likely originated in a minor merger with a smaller galaxy, although dynamical ejection from the host nucleus cannot yet be ruled out. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_16093 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | JWST and Keck observations of the off-nuclear tidal disruption event TDE 2025abcr: An evolving reprocessing layer Patra, Kishore C. Liepold, Emily R. Earl, Nicholas Foley, Ryan J. Ma, Chung-Pei Gomez, Sebastian Davis, Kyle W. Ramirez-Ruiz, Enrico French, K. Decker Walsh, Jonelle L. Kaur, Ravjit Taggart, Kirsty Candanoza, Joshua Villar, V. Ashley Arunachalam, Prasiddha Macias, Phillip Tinyanont, Samaporn High Energy Astrophysical Phenomena Astrophysics of Galaxies Off-nuclear tidal disruption events (TDEs) provide a rare probe of massive black holes (MBHs) outside galactic nuclei. Only a handful are known, including five X-ray-selected candidates and two optically selected events. We present observations of TDE 2025abcr, the second optically selected off-nuclear TDE, discovered at a projected offset of $9.08 \pm 0.02$ kpc from the nucleus of its host galaxy. We analyze X-ray, UV, optical, and infrared (IR) data from Swift, Keck, ZTF, and JWST. Broad H and He emission lines in the optical and IR confirm a TDE-H-He classification. From luminosity scaling relations and MOSFiT modeling, we infer a BH mass of $10^{6}$-$10^{7}\,M_{\odot}$, substantially smaller than the $10^{8.35 \pm 0.41}\,M_{\odot}$ BH inferred for the host-galaxy nucleus. We observe velocity evolution in the N III + He II emission complex, shifting from $-500$ km s$^{-1}$ at day $-7$ to $+1000$ km s$^{-1}$ by day $+29$, which we interpret as radiative transfer effects in an evolving reprocessing layer. The IR SED deviates from a thermal blackbody, with $νL_ν \propto λ^{-2.13 \pm 0.04}$, significantly shallower than the Rayleigh-Jeans slope of $λ^{-3}$. We rule out dust as the source of this IR excess. Two possibilities remain: free-free emission from reprocessing gas, or an unresolved stellar cluster at the TDE location. Reprocessed emission provides a natural explanation for the IR excess but an underlying stellar cluster of mass $\log(M_{*}/M_{\odot}) = 7.57 \pm 0.02$ and age $<$2 Gyr is also consistent with the data. If interpreted as a stellar cluster, the inferred mass suggests a stripped remnant of a satellite galaxy. The wandering MBH most likely originated in a minor merger with a smaller galaxy, although dynamical ejection from the host nucleus cannot yet be ruled out. |
| title | JWST and Keck observations of the off-nuclear tidal disruption event TDE 2025abcr: An evolving reprocessing layer |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2604.16093 |