前主序变量V2492 Cyg的2016-2017年峰值光度
The 2016-2017 peak luminosity of the pre-main sequence variable V2492 Cyg
摘要：
天鹅座V2492是一颗年轻的前主序星，呈现出明显的亮度变化（Δ R > 5等），其物理起源被认为是由消光（UXor型）和吸积（EXor型）的变化引起的，尽管它们之间的比例还没有得到澄清。最近，V2492 Cyg已经达到了其记录活动期间记录的亮度水平。2016年10月和2017年3月至7月期间获得了光学和近红外测光和光谱。直到2017年5月底，该源一直保持明亮，然后从6月初开始以约0.08 mag/天的速度迅速减弱。2017年7月中旬，该光源达到了与两年前相同的低亮度水平。消光率和质量吸积率是通过最亮谱线的光度，特别是H α和H β得到的。一对夫妇的光学高分辨率光谱也提出了推导信息的气体运动学。可见光消光的变化不会超过几个星等，而质量吸积速率的变化估计从小于10^-8到几个10^-7 M_sun/yr不等。后者与2010年之前的高状态估计相当，可能发生在更严重的灭绝条件下。光学和近红外（NIR）观测的综合分析扩展到目前的事件，原来的建议，V2492天鹅座的变化是一个不断变化的消光和吸积的组合。
英文摘要：
V2492 Cyg is a young pre-main sequence star presenting repetitive brightness variations of significant amplitude (Delta R > 5 mag) whose physical origin has been ascribed to both extinction (UXor-type) and accretion (EXor-type) variability, although their mutual proportion has not been clarified yet. Recently, V2492 Cyg has reached a level of brightness ever registered in the period of its documented activity. Optical and near-infrared photometry and spectroscopy have been obtained in October 2016 and between March and July 2017. The source has remained bright until the end of May 2017, then it started to rapidly fade since the beginning of June at a rate of about 0.08 mag/day. On mid-July 2017 the source has reached the same low-brightness level as two years before. Extinction and mass accretion rate were derived by means of the luminosity of the brightest lines, in particular Halpha and Hbeta. A couple of optical high-resolution spectra are also presented to derive information on the gas kinematics. Visual extinction variations do not exceed a few magnitudes, while the mass accretion rate is estimated to vary from less than 10^-8 up to a few 10^-7 M_sun/yr. This latter is comparable to that estimated on the previous high-state in 2010, likely occurred under more severe extinction conditions. The combined analysis of the optical and near-infrared (NIR) observations extends to the present event the original suggestion that the V2492 Cyg variability is a combination of changing extinction and accretion.
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