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A Comprehensive X-Ray Report on AT2019wey

Yao, Yuhan and Kulkarni, S. R. and Gendreau, K. C. and Jaisawal, Gaurava K. and Enoto, Teruaki and Grefenstette, Brian W. and Marshall, Herman L. and García, Javier A. and Ludlam, R. M. and Pike, Sean N. and Ng, Mason and Zhang, Liang and Altamirano, Diego and Jaodand, Amruta and Cenko, S. Bradley and Remillard, Ronald A. and Steiner, James F. and Negoro, Hitoshi and Brightman, Murray and Lien, Amy and Wolff, Michael T. and Ray, Paul S. and Mukai, Koji and Wadiasingh, Zorawar and Arzoumanian, Zaven and Kawai, Nobuyki and Mihara, Tatehiro and Strohmayer, Tod E. (2021) A Comprehensive X-Ray Report on AT2019wey. Astrophysical Journal, 920 (2). Art. No. 121. ISSN 0004-637X. doi:10.3847/1538-4357/ac15f8.

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Here, we present MAXI, Swift, NICER, NuSTAR, and Chandra observations of the X-ray transient AT2019wey (SRGA J043520.9+552226, SRGE J043523.3+552234). From spectral and timing analyses we classify it as a Galactic low-mass X-ray binary (LMXB) with a black hole (BH) or neutron star (NS) accretor. AT2019wey stayed in the low/hard state (LHS) from 2019 December to 2020 August 21, and the hard-intermediate state (HIMS) from 2020 August 21 to 2020 November. For the first six months of the LHS, AT2019wey had a flux of ∼1 mCrab, and displayed a power-law X-ray spectrum with photon index Γ = 1.8. From 2020 June to August, it brightened to ∼20 mCrab. Spectral features characteristic of relativistic reflection became prominent. On 2020 August 21, the source left the "hard line" on the rms–intensity diagram, and transitioned from LHS to HIMS. The thermal disk component became comparable to the power-law component. A low-frequency quasi-periodic oscillation (QPO) was observed. The QPO central frequency increased as the spectrum softened. No evidence of pulsation was detected. We are not able to decisively determine the nature of the accretor (BH or NS). However, the BH option is favored by the position of this source on the Γ–L_X, L_(radio)–L_X, and L_(opt)–L_X diagrams. We find the BH candidate XTE J1752−223 to be an analog of AT2019wey. Both systems display outbursts with long plateau phases in the hard states. We conclude by noting the potential of SRG in finding new members of this emerging class of low luminosity and long-duration LMXB outbursts.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Yao, Yuhan0000-0001-6747-8509
Kulkarni, S. R.0000-0001-5390-8563
Gendreau, K. C.0000-0001-7115-2819
Jaisawal, Gaurava K.0000-0002-6789-2723
Enoto, Teruaki0000-0003-1244-3100
Grefenstette, Brian W.0000-0002-1984-2932
Marshall, Herman L.0000-0002-6492-1293
García, Javier A.0000-0003-3828-2448
Ludlam, R. M.0000-0002-8961-939X
Pike, Sean N.0000-0002-8403-0041
Ng, Mason0000-0002-0940-6563
Zhang, Liang0000-0003-4498-9925
Altamirano, Diego0000-0002-3422-0074
Jaodand, Amruta0000-0002-3850-6651
Cenko, S. Bradley0000-0003-1673-970X
Remillard, Ronald A.0000-0003-4815-0481
Steiner, James F.0000-0002-5872-6061
Negoro, Hitoshi0000-0003-0939-1178
Brightman, Murray0000-0002-8147-2602
Lien, Amy0000-0002-7851-9756
Wolff, Michael T.0000-0002-4013-5650
Ray, Paul S.0000-0002-5297-5278
Wadiasingh, Zorawar0000-0002-9249-0515
Kawai, Nobuyki0000-0001-9656-0261
Mihara, Tatehiro0000-0002-6337-7943
Strohmayer, Tod E.0000-0001-7681-5845
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 30; revised 2021 April 6; accepted 2021 April 14; published 2021 October 21. We thank the anonymous reviewer for providing comments that have largely improved this manuscript. We thank Belinda Wilkes and Patrick Slane for allocating DD time on Chandra, and Fiona Harrison for allocating NuSTAR DD time. We thank Kumiko Morihana for providing the cleaned MAXI light curve of MAXI J1305−704. Y.Y. thanks the Heising-Simons Foundation for support. R.M.L. acknowledges the support of NASA through the Hubble Fellowship Program grant HST-HF2-51440.001. J.A.G. acknowledges support from NASA grant 80NSSC17K0515 and from the Alexander von Humboldt Foundation. Z.W. acknowledges support from the NASA postdoctoral program. NICER research at NRL is supported by NASA. This work was partially supported under NASA contract No. NNG08FD60C and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (nustardas), jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Facilities: NICER - , NuSTAR - , CXO (ACIS-S) - , Swift (XRT - , BAT) - , MAXI. - Software: astropy (Astropy Collaboration et al. 2013), CIAO (Fruscione et al. 2006), HEASoft (v6.27; Heasarc 2014), HENDRICS (Bachetti 2015), isis (Houck & Denicola 2000), matplotlib (Hunter 2007), pandas (McKinney 2010), PRESTO (Ransom 2011); relxill (v1.3.10; García et al. 2014; Dauser et al. 2014) Stingray (Huppenkothen et al. 2019), xspec (v12.11.0; Arnaud 1996).
Group:Astronomy Department, Space Radiation Laboratory, NuSTAR
Funding AgencyGrant Number
Heising-Simons FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51440.001
Alexander von Humboldt FoundationUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
NASA Einstein FellowshipUNSPECIFIED
Subject Keywords:Accretion; Black holes; Low-mass x-ray binary stars; X-ray transient sources; Transient sources; X-ray sources; X-ray binary stars
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Accretion (14); Black holes (162); Low-mass x-ray binary stars (939); Xray transient sources (1852); Transient sources (1851); X-ray sources (1822); X-ray binary stars (1811)
Record Number:CaltechAUTHORS:20210106-131324406
Persistent URL:
Official Citation:Yuhan Yao et al 2021 ApJ 920 121
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107349
Deposited By: George Porter
Deposited On:08 Jan 2021 22:00
Last Modified:04 Nov 2021 20:34

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