The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System
We present X-ray, UV, optical, and radio observations of the nearby (≈78 Mpc) tidal disruption event AT2021ehb/ZTF21aanxhjv during its first 430 days of evolution. AT2021ehb occurs in the nucleus of a galaxy hosting a≈107 M ⊙ black hole (M BH inferred from host galaxy scaling relations). High-cadenc...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Language: | English |
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IOP Publishing Ltd
2022
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| Online Access: | http://dx.doi.org/10.3847/1538-4357/ac898a http://hdl.handle.net/20.500.11937/97227 |
| _version_ | 1848766242537603072 |
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| author | Yao, Y. Lu, W. Guolo, M. Pasham, D.R. Gezari, S. Gilfanov, M. Gendreau, K.C. Harrison, F. Cenko, S.B. Kulkarni, S.R. Miller, J.M. Walton, D.J. García, J.A. Velzen, S.V. Alexander, K.D. Miller-Jones, James Nicholl, M. Hammerstein, E. Medvedev, P. Stern, D. Ravi, V. Sunyaev, R. Bloom, J.S. Graham, M.J. Kool, E.C. Mahabal, A.A. Masci, F.J. Purdum, J. Rusholme, B. Sharma, Y. Smith, R. Sollerman, J. |
| author_facet | Yao, Y. Lu, W. Guolo, M. Pasham, D.R. Gezari, S. Gilfanov, M. Gendreau, K.C. Harrison, F. Cenko, S.B. Kulkarni, S.R. Miller, J.M. Walton, D.J. García, J.A. Velzen, S.V. Alexander, K.D. Miller-Jones, James Nicholl, M. Hammerstein, E. Medvedev, P. Stern, D. Ravi, V. Sunyaev, R. Bloom, J.S. Graham, M.J. Kool, E.C. Mahabal, A.A. Masci, F.J. Purdum, J. Rusholme, B. Sharma, Y. Smith, R. Sollerman, J. |
| author_sort | Yao, Y. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We present X-ray, UV, optical, and radio observations of the nearby (≈78 Mpc) tidal disruption event AT2021ehb/ZTF21aanxhjv during its first 430 days of evolution. AT2021ehb occurs in the nucleus of a galaxy hosting a≈107 M ⊙ black hole (M BH inferred from host galaxy scaling relations). High-cadence Swift and Neutron Star Interior Composition Explorer (NICER) monitoring reveals a delayed X-ray brightening. The spectrum first undergoes a gradual soft → hard transition and then suddenly turns soft again within 3 days at δ t≈272 days during which the X-ray flux drops by a factor of 10. In the joint NICER+NuSTAR observation (δ t = 264 days, harder state), we observe a prominent nonthermal component up to 30 keV and an extremely broad emission line in the iron K band. The bolometric luminosity of AT2021ehb reaches a maximum of 6.0 − 3.8 + 10.4 % L Edd when the X-ray spectrum is the hardest. During the dramatic X-ray evolution, no radio emission is detected, the UV/optical luminosity stays relatively constant, and the optical spectra are featureless. We propose the following interpretations: (i) the soft → hard transition may be caused by the gradual formation of a magnetically dominated corona; (ii) hard X-ray photons escape from the system along solid angles with low scattering optical depth (∼a few) whereas the UV/optical emission is likely generated by reprocessing materials with much larger column density—the system is highly aspherical; and (iii) the abrupt X-ray flux drop may be triggered by the thermal-viscous instability in the inner accretion flow, leading to a much thinner disk. |
| first_indexed | 2025-11-14T11:48:02Z |
| format | Journal Article |
| id | curtin-20.500.11937-97227 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-14T11:48:02Z |
| publishDate | 2022 |
| publisher | IOP Publishing Ltd |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-972272025-04-30T01:33:13Z The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System Yao, Y. Lu, W. Guolo, M. Pasham, D.R. Gezari, S. Gilfanov, M. Gendreau, K.C. Harrison, F. Cenko, S.B. Kulkarni, S.R. Miller, J.M. Walton, D.J. García, J.A. Velzen, S.V. Alexander, K.D. Miller-Jones, James Nicholl, M. Hammerstein, E. Medvedev, P. Stern, D. Ravi, V. Sunyaev, R. Bloom, J.S. Graham, M.J. Kool, E.C. Mahabal, A.A. Masci, F.J. Purdum, J. Rusholme, B. Sharma, Y. Smith, R. Sollerman, J. Science & Technology Physical Sciences Astronomy & Astrophysics X-RAY SOURCES SUPERMASSIVE BLACK-HOLES GALACTIC NUCLEI ACCRETION FLOWS FUNDAMENTAL PLANE EDDINGTON RATIO ENERGY-SPECTRA BINARY-SYSTEMS LOW-RESOLUTION LINE SPECTRA astro-ph.HE astro-ph.HE We present X-ray, UV, optical, and radio observations of the nearby (≈78 Mpc) tidal disruption event AT2021ehb/ZTF21aanxhjv during its first 430 days of evolution. AT2021ehb occurs in the nucleus of a galaxy hosting a≈107 M ⊙ black hole (M BH inferred from host galaxy scaling relations). High-cadence Swift and Neutron Star Interior Composition Explorer (NICER) monitoring reveals a delayed X-ray brightening. The spectrum first undergoes a gradual soft → hard transition and then suddenly turns soft again within 3 days at δ t≈272 days during which the X-ray flux drops by a factor of 10. In the joint NICER+NuSTAR observation (δ t = 264 days, harder state), we observe a prominent nonthermal component up to 30 keV and an extremely broad emission line in the iron K band. The bolometric luminosity of AT2021ehb reaches a maximum of 6.0 − 3.8 + 10.4 % L Edd when the X-ray spectrum is the hardest. During the dramatic X-ray evolution, no radio emission is detected, the UV/optical luminosity stays relatively constant, and the optical spectra are featureless. We propose the following interpretations: (i) the soft → hard transition may be caused by the gradual formation of a magnetically dominated corona; (ii) hard X-ray photons escape from the system along solid angles with low scattering optical depth (∼a few) whereas the UV/optical emission is likely generated by reprocessing materials with much larger column density—the system is highly aspherical; and (iii) the abrupt X-ray flux drop may be triggered by the thermal-viscous instability in the inner accretion flow, leading to a much thinner disk. 2022 Journal Article http://hdl.handle.net/20.500.11937/97227 10.3847/1538-4357/ac898a English http://dx.doi.org/10.3847/1538-4357/ac898a http://purl.org/au-research/grants/arc/DP200102471 http://creativecommons.org/licenses/by/4.0/ IOP Publishing Ltd fulltext |
| spellingShingle | Science & Technology Physical Sciences Astronomy & Astrophysics X-RAY SOURCES SUPERMASSIVE BLACK-HOLES GALACTIC NUCLEI ACCRETION FLOWS FUNDAMENTAL PLANE EDDINGTON RATIO ENERGY-SPECTRA BINARY-SYSTEMS LOW-RESOLUTION LINE SPECTRA astro-ph.HE astro-ph.HE Yao, Y. Lu, W. Guolo, M. Pasham, D.R. Gezari, S. Gilfanov, M. Gendreau, K.C. Harrison, F. Cenko, S.B. Kulkarni, S.R. Miller, J.M. Walton, D.J. García, J.A. Velzen, S.V. Alexander, K.D. Miller-Jones, James Nicholl, M. Hammerstein, E. Medvedev, P. Stern, D. Ravi, V. Sunyaev, R. Bloom, J.S. Graham, M.J. Kool, E.C. Mahabal, A.A. Masci, F.J. Purdum, J. Rusholme, B. Sharma, Y. Smith, R. Sollerman, J. The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title | The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title_full | The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title_fullStr | The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title_full_unstemmed | The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title_short | The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk-Corona System |
| title_sort | tidal disruption event at2021ehb: evidence of relativistic disk reflection, and rapid evolution of the disk-corona system |
| topic | Science & Technology Physical Sciences Astronomy & Astrophysics X-RAY SOURCES SUPERMASSIVE BLACK-HOLES GALACTIC NUCLEI ACCRETION FLOWS FUNDAMENTAL PLANE EDDINGTON RATIO ENERGY-SPECTRA BINARY-SYSTEMS LOW-RESOLUTION LINE SPECTRA astro-ph.HE astro-ph.HE |
| url | http://dx.doi.org/10.3847/1538-4357/ac898a http://dx.doi.org/10.3847/1538-4357/ac898a http://hdl.handle.net/20.500.11937/97227 |