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Multi-wavelength Observations of AT2019wey: a New Candidate Black Hole Low-mass X-ray Binary

Yao, Yuhan and Kulkarni, S. R. and Burdge, Kevin B. and Caiazzo, Ilaria and De, Kishalay and Dong, Dillon and Fremling, C. and Kasliwal, Mansi M. and Kupfer, Thomas and van Roestel, Jan and Sollerman, Jesper and Bagdasaryan, Ashot and Bellm, Eric C. and Cenko, S. Bradley and Drake, Andrew J. and Duev, Dmitry A. and Graham, Matthew J. and Kaye, Stephen and Masci, Frank J. and Miranda, Nicolas and Prince, Thomas A. and Riddle, Reed and Rusholme, Ben and Soumagnac, Maayane T. (2021) Multi-wavelength Observations of AT2019wey: a New Candidate Black Hole Low-mass X-ray Binary. Astrophysical Journal, 920 (2). Art. No. 120. ISSN 0004-637X. doi:10.3847/1538-4357/ac15f9.

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AT2019wey (SRGA J043520.9+552226, SRGE J043523.3+552234) is a transient first reported by the ATLAS optical survey in 2019 December. It rose to prominence upon detection, three months later, by the Spektrum-Roentgen-Gamma (SRG) mission in its first all-sky survey. X-ray observations reported in Yao et al. suggest that AT2019wey is a Galactic low-mass X-ray binary (LMXB) with a black hole (BH) or neutron star (NS) accretor. Here we present ultraviolet, optical, near-infrared, and radio observations of this object. We show that the companion is a short-period (P ≲ 16 hr) low-mass (<1 M_⊙) star. We consider AT2019wey to be a candidate BH system since its locations on the L_(radio)–L_X and L_(opt)–L_X diagrams are closer to BH binaries than NS binaries. We demonstrate that from 2020 June to August, despite the more than 10 times brightening at radio and X-ray wavelengths, the optical luminosity of AT2019wey only increased by 1.3–1.4 times. We interpret the UV/optical emission before the brightening as thermal emission from a truncated disk in a hot accretion flow and the UV/optical emission after the brightening as reprocessing of the X-ray emission in the outer accretion disk. AT2019wey demonstrates that combining current wide-field optical surveys and SRG provides a way to discover the emerging population of short-period BH LMXB systems with faint X-ray outbursts.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Yao, Yuhan0000-0001-6747-8509
Kulkarni, S. R.0000-0001-5390-8563
Burdge, Kevin B.0000-0002-7226-836X
Caiazzo, Ilaria0000-0002-4770-5388
De, Kishalay0000-0002-8989-0542
Dong, Dillon0000-0001-9584-2531
Fremling, C.0000-0002-4223-103X
Kasliwal, Mansi M.0000-0002-5619-4938
Kupfer, Thomas0000-0002-6540-1484
van Roestel, Jan0000-0002-2626-2872
Sollerman, Jesper0000-0003-1546-6615
Bellm, Eric C.0000-0001-8018-5348
Cenko, S. Bradley0000-0003-1673-970X
Duev, Dmitry A.0000-0001-5060-8733
Graham, Matthew J.0000-0002-3168-0139
Masci, Frank J.0000-0002-8532-9395
Miranda, Nicolas0000-0001-6070-7540
Prince, Thomas A.0000-0002-8850-3627
Riddle, Reed0000-0002-0387-370X
Rusholme, Ben0000-0001-7648-4142
Soumagnac, Maayane T.0000-0001-6753-1488
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 30; revised 2021 July 2; accepted 2021 July 16; published 2021 October 21. We thank the anonymous reviewer for providing comments that have significantly improved this manuscript. We thank Mark McKinnon and Amy Mioduszewski for allocating DD time on VLA. We thank Jie Lin and Stephen Smartt for helpful comments. Y.Y. is supported in part by the Heising-Simons Foundation. M.M.K. acknowledges generous support from the David and Lucille Packard Foundation. E.C.B. is supported in part by the NSF AAG grant 1812779 and grant #2018-0908 from the Heising-Simons Foundation. This work is based on observations obtained with the 48-inch Samuel Oschin Telescope and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. The ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. This work was supported by the GROWTH project funded by the National Science Foundation under grant No. 1545949. The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queens University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. We acknowledge ESA Gaia, DPAC, and the Photometric Science Alerts Team ( Facilities: PO:1.2 m (ZTF - , iPTF - , POSS) - , PO:1.5 m (SEDM) - , Gaia - , Hale (DBSP - , CHIMERA) - , Keck:I (LRIS) - , Keck:II (ESI - , NIRES) - , VLA - , MAXI - , Swift (UVOT - , XRT) - , NICER - , Sloan - , PS1 - . Software: astropy (Astropy Collaboration et al. 2013), CASA (v5.6.1; McMullin et al. 2007), diskir (Gierliński et al. 2008, 2009), emcee (Foreman-Mackey et al. 2013), FPipe (Fremling et al. 2016), HEASoft (v6.27; Heasarc 2014), LPipe (Perley 2019), makee (, matplotlib (Hunter 2007), pandas (McKinney 2010), pyraf-dbsp pipeline (Bellm & Sesar 2016), scipy (Virtanen et al. 2020), spextool (Cushing et al. 2004), XRB-LrLx_pub (Bahramian et al. 2018,, xspec (v12.11.0; Arnaud 1996) xtellcor (Vacca et al. 2003).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Heising-Simons Foundation2018-0908
David and Lucile Packard FoundationUNSPECIFIED
ZTF partner institutionsUNSPECIFIED
Heising-Simons Foundation12540303
Science and Technology Facilities Council (STFC)ST/T000198/1
Science and Technology Facilities Council (STFC)ST/S006109/1
Subject Keywords:Low-mass x-ray binary stars; Accretion; Astrophysical black holes; Sky surveys
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Low-mass x-ray binary stars (939); Accretion (14); Astrophysical black holes (98); Sky surveys (1464)
Record Number:CaltechAUTHORS:20210106-131320879
Persistent URL:
Official Citation:Yuhan Yao et al 2021 ApJ 920 120
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107348
Deposited By: George Porter
Deposited On:08 Jan 2021 22:10
Last Modified:04 Nov 2021 16:05

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