Unusual Hard X-Ray Flares Caught in NICER Monitoring of the Binary Supermassive Black Hole Candidate AT2019cuk/Tick Tock/SDSS J1430+2303
Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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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. / Masterson, Megan; Kara, Erin; Pasham, Dheeraj R.; D'Orazio, Daniel J.; Walton, Dominic J.; Fabian, Andrew C.; Lucchini, Matteo; Remillard, Ronald A.; Arzoumanian, Zaven; Burkhonov, Otabek; Choi, Hyeonho; Ehgamberdiev, Shuhrat A.; Ferrara, Elizabeth C.; Guolo, Muryel; Im, Myungshin; Kim, Yonggi; Mirzaqulov, Davron O.; Paek, Gregory S. H.; Sung, Hyun-Il; Yoon, Joh-Na.
I: Astrophysical Journal Letters, Bind 945, Nr. 2, 34, 01.03.2023.Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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TY - JOUR
T1 - Unusual Hard X-Ray Flares Caught in NICER Monitoring of the Binary Supermassive Black Hole Candidate AT2019cuk/Tick Tock/SDSS J1430+2303
AU - Masterson, Megan
AU - Kara, Erin
AU - Pasham, Dheeraj R.
AU - D'Orazio, Daniel J.
AU - Walton, Dominic J.
AU - Fabian, Andrew C.
AU - Lucchini, Matteo
AU - Remillard, Ronald A.
AU - Arzoumanian, Zaven
AU - Burkhonov, Otabek
AU - Choi, Hyeonho
AU - Ehgamberdiev, Shuhrat A.
AU - Ferrara, Elizabeth C.
AU - Guolo, Muryel
AU - Im, Myungshin
AU - Kim, Yonggi
AU - Mirzaqulov, Davron O.
AU - Paek, Gregory S. H.
AU - Sung, Hyun-Il
AU - Yoon, Joh-Na
PY - 2023/3/1
Y1 - 2023/3/1
N2 - 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.
AB - 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.
KW - ACTIVE GALACTIC NUCLEUS
KW - QUASI-PERIODIC ERUPTIONS
KW - TIDAL DISRUPTION
KW - SYSTEMATIC SEARCH
KW - LIGHT CURVES
KW - XMM-NEWTON
KW - DUAL AGNS
KW - NUSTAR
KW - SWIFT
KW - VARIABILITY
U2 - 10.3847/2041-8213/acbea9
DO - 10.3847/2041-8213/acbea9
M3 - Letter
VL - 945
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - 34
ER -
ID: 342497751