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Unusual Hard X-Ray Flares Caught in NICER Monitoring of the Binary Supermassive Black Hole Candidate AT2019cuk/Tick Tock/SDSS J1430+2303

Megan MastersonMIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected]Erin KaraMIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected]Dheeraj R. PashamMIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected]Daniel J. D’OrazioNiels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen, DenmarkD. J. WaltonCentre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UKA. C. FabianInstitute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UKMatteo LucchiniMIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected]Ronald A. RemillardMIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; [email protected]Zaven ArzoumanianX-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 662, Greenbelt, Maryland 20771, USAО. БурхоновUlugh Beg Astronomical Institute, Astronomy Street 33, Tashkent 100052, UzbekistanHyeonho ChoiSNU Astronomy Research Center, Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic Of KoreaSh. A. EhgamberdievNational University of Uzbekistan, Tashkent 100174, UzbekistanE. C. FerraraCenter for Exploration and Space Studies (CRESST), NASA/GSFC, Greenbelt, MD 20771, USAMuryel GuoloDepartment of Physics and Astronomy, Johns Hopkins University, 400 N. Charles Street, Baltimore, MD 21218, USAMyungshin ImSNU Astronomy Research Center, Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic Of KoreaYonggi KimDepartment of Astronomy and Space Science, Chungbuk National University Observatory, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic Of KoreaD. O. MirzaqulovUlugh Beg Astronomical Institute, Astronomy Street 33, Tashkent 100052, UzbekistanGregory S. H. PaekSNU Astronomy Research Center, Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Republic Of KoreaHyun-Il SungKorea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic Of KoreaJoh-Na YoonDepartment of Astronomy and Space Science, Chungbuk National University Observatory, Chungdae-ro 1, Seowon-Gu, Cheongju, Chungbuk 28644, Republic Of Korea

The Astrophysical Journal Lettersjournal2023en

ABI

Аннотация

Abstract The nuclear transient AT2019cuk/Tick Tock/SDSS J1430+2303 has been suggested to harbor a supermassive black hole (SMBH) binary near coalescence. We report results from high-cadence NICER X-ray monitoring with multiple visits per day from 2022 January to August, as well as continued optical monitoring during the same time period. We find no evidence of periodic/quasiperiodic modulation in the X-ray, UV, or optical bands; however, we do observe exotic hard X-ray variability that is unusual for typical active galactic nuclei (AGN). The most striking feature of the NICER light curve is repetitive hard (2–4 keV) X-ray flares that result in distinctly harder X-ray spectra compared to the nonflaring data. In its nonflaring state, AT2019cuk looks like a relatively standard AGN, but it presents the first case of day-long, hard X-ray flares in a changing-look AGN. We consider a few different models for the driving mechanism of these hard X-ray flares, including (1) corona/jet variability driven by increased magnetic activity, (2) variable obscuration, and (3) self-lensing from the potential secondary SMBH. We prefer the variable corona model, as the obscuration model requires rather contrived timescales and the self-lensing model is difficult to reconcile with a lack of clear periodicity in the flares. These findings illustrate how important high-cadence X-ray monitoring is to our understanding of the rapid variability of the X-ray corona and necessitate further high-cadence, multiwavelength monitoring of changing-look AGN like AT2019cuk to probe the corona-jet connection.

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Мавзулар

Astrophysical Phenomena and Observations Astrophysics and Cosmic Phenomena Pulsars and Gravitational Waves Research

Идентификаторлар

DOI: 10.3847/2041-8213/acbea9

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