Preprint article · Journal article
A Comprehensive X-Ray Report on AT2019wey
California Institute of Technology1
Naval Research Laboratory2
University of Maryland, Baltimore County3
Tokyo Institute of Technology4
NASA Goddard Space Flight Center5
National Space Institute, Technical University of Denmark6
Astrophysics and Atmospheric Physics, National Space Institute, Technical University of Denmark7
RIKEN8
Massachusetts Institute of Technology9
University of Southampton10
Harvard University11
Nihon University12
...and 2 moreHere, 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–LX, Lradio–LX, and Lopt–LX 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.
Language: | English |
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Publisher: | American Astronomical Society |
Year: | 2021 |
Pages: | 121 |
ISSN: | 15384357 and 0004637x |
Types: | Preprint article and Journal article |
DOI: | 10.3847/1538-4357/ac15f8 |
ORCIDs: | 0000-0001-6747-8509 , 0000-0001-5390-8563 , 0000-0001-7115-2819 , Jaisawal, Gaurava K. , 0000-0003-1244-3100 , 0000-0002-1984-2932 , 0000-0002-6492-1293 , 0000-0003-3828-2448 , 0000-0002-8961-939X , 0000-0002-8403-0041 , 0000-0002-0940-6563 , 0000-0003-4498-9925 , 0000-0002-3422-0074 , 0000-0002-3850-6651 , 0000-0003-1673-970X , 0000-0003-4815-0481 , 0000-0003-0939-1178 , 0000-0002-8147-2602 , 0000-0002-4013-5650 , 0000-0002-5297-5278 , 0000-0002-8286-8094 , 0000-0002-9249-0515 , 0000-0001-9656-0261 , 0000-0002-6337-7943 and 0000-0001-7681-5845 |