Статья

The Curious Case of ASASSN-20hx: A Slowly Evolving, UV- and X-Ray-Luminous, Ambiguous Nuclear Transient

Jason T. HinkleInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAT. W. S. HoloienThe Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101, USAB. J. ShappeeInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAJack M. M. NeustadtDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAKatie AuchettlARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), AustraliaPatrick J. VallelyDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAMelissa ShahbandehDepartment of Physics, Florida State University, 77 Chieftan Way, Tallahassee, FL 32306, USAMatthias KlugeMax Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, D-85748 Garching, GermanyC. S. KochanekCenter for Cosmology and Astroparticle Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USAK. Z. StanekCenter for Cosmology and Astroparticle Physics, The Ohio State University, 191 W. Woodruff Avenue, Columbus, OH 43210, USAM. E. HuberInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAR. S. PostPost Observatory, Lexington, MA 02421, USAD. BersierAstrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UKC. AshallInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAM. A. TuckerInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAJonathan P. WilliamsInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAThomas de JaegerInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAA. DoInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAMichael FausnaughDepartment of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USAD. GruenUniversity-Observatory, Ludwig-Maximilians-University, Scheinerstrasse 1, D-81679 Munich, GermanyU. HoppUniversity-Observatory, Ludwig-Maximilians-University, Scheinerstrasse 1, D-81679 Munich, GermanyJ. MylesDepartment of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94305, USAChristian ObermeierMax Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, D-85748 Garching, GermanyA. V. PayneInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USATodd A. ThompsonDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA

2022en

ABI

Аннотация

Abstract We present observations of ASASSN-20hx, a nearby ambiguous nuclear transient (ANT) discovered in NGC 6297 by the All-Sky Automated Survey for Supernovae (ASAS-SN). We observed ASASSN-20hx from −30 to 275 days relative to the peak UV/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From Transiting Exoplanet Survey Satellite data, we determine that the ANT began to brighten on 2020 June 22.8 with a linear rise in flux for at least the first week. ASASSN-20hx peaked in the UV/optical 30 days later on 2020 July 22.8 (MJD = 59052.8) at a bolometric luminosity of L = (3.15 ± 0.04) × 10 43 erg s −1 . The subsequent decline is slower than any TDE observed to date and consistent with many other ANTs. Compared to an archival X-ray detection, the X-ray luminosity of ASASSN-20hx increased by an order of magnitude to L x ∼ 1.5 × 10 42 erg s −1 and then slowly declined over time. The X-ray emission is well fit by a power law with a photon index of Γ ∼ 2.3–2.6. Both the optical and near-infrared spectra of ASASSN-20hx lack emission lines, unusual for any known class of nuclear transient. While ASASSN-20hx has some characteristics seen in both tidal disruption events and active galactic nuclei, it cannot be definitively classified with current data.

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Идентификаторы

DOI: 10.3847/1538-4357/ac5f54

Цитирования и источники

Цитирований: 2Использованных источников: 0

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