标题： AT2019wey的多波长观测：一个新的低质量X射线双星黑洞候选体 显示英文标题

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

摘要： AT2019wey（SRGA J043520.9+552226，SRGE J043523.3+552234）是一个首次由ATLAS光学调查在2019年12月报告的暂现源。 在三个月后，该源被Spektrum-Roentgen-Gamma（SRG）任务在其首次全天巡天中检测到而受到关注。 Yao等人报告的X射线观测表明，AT2019wey是一个银河系低质量X射线双星（LMXB），其中心天体可能是黑洞（BH）或中子星（NS）。 在这里，我们展示了该天体的紫外、光学、近红外和射电观测数据。 我们表明，伴星是一个短周期（P < 16小时）低质量（< 1 Msun）恒星。 我们认为AT2019wey是一个候选黑洞系统，因为其在L_radio--L_X和L_opt--L_X图上的位置更接近黑洞双星而非中子星双星。 我们证明，在2020年6月至8月期间，尽管射电和X射线波段的亮度增加了10倍以上，AT2019wey的光学光度仅增加了1.3至1.4倍。 我们将亮化前的紫外/光学辐射解释为热辐射来自热吸积流中的截断盘，而亮化后的紫外/光学辐射则是外吸积盘对X射线辐射的再处理。 AT2019wey表明，结合当前的广域光学调查和SRG可以提供一种发现具有微弱X射线爆发的短周期黑洞LMXB系统的途径。 显示英文摘要

摘要： 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 Msun) 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.