Be/X射线双星V850 Cen/GX 304-1在弱X射线周期活动期间的光谱学
Optical spectroscopy of the Be/X-ray Binary V850 Cen/GX 304-1 during faint X-ray periodical activity
摘要：
Be/X射线双星是大质量X射线双星中数量最多的一类。它们的X射线占空比与光学伴风活动密切相关，而光学伴风活动又可以通过专门的光学光谱观测进行研究。我们研究了Be星周盘的光谱特征，以检验其长期变化及其与X射线活动的关系。特别注意的是H $α$发射线，这是最好的示踪剂的磁盘条件之一。我们从2014-2015年的英澳望远镜和南部非洲大型望远镜的专门活动中获得了光学宽带中分辨率光谱。数据跨越整个双星轨道，涵盖X射线静止期和中等活跃期。我们用巴耳末辐射线来跟踪星周盘的演化。我们观察到突出的光谱特征，如双峰H $α$和H $β$发射线。H $α$ V/R比在约一年的时间尺度上显著变化。我们的观测结果与在大倾角（$i\gtrsim60^{\circ}$）下观测到的系统一致。导出的拱星盘的大小表明，磁盘从一个配置，防止吸积到中子星，一个只允许适度的吸积。这与当时观测到的X射线活动是一致的。我们的研究结果被解释的背景下，低效的潮汐截断的拱盘，预期这个源的二进制配置。我们推导出H $β$发射区的大小，这导致大约一半的相应的H $α$发射盘，并限制V850 Cen的光度类别为III-V，与先前提出的类别一致。
英文摘要：
Be/X-ray binaries are the most populous class of High Mass X-ray Binaries. Their X-ray duty cycle is tightly related to the optical companion wind activity, which in turn can be studied through optical spectroscopical dedicated observations. We study optical spectral features of the Be circumstellar disk to test their long-term variability and their relation with the X-ray activity. Special attention has been given to the H$α$ emission line, that is one of the best tracers of the disk conditions. We obtained optical broadband medium resolution spectra from a dedicated campaign with the Anglo-Australian Telescope and the Southern African Large Telescope in 2014-2015. Data span over one entire binary orbit, and cover both X-ray quiescent and moderately active periods. We used Balmer emission lines to follow the evolution of the circumstellar disk. We observe prominent spectral features, like double-peaked H$α$ and H$β$ emission lines. The H$α$ V/R ratio significantly changes over a time scale of about one year. Our observations are consistent with a system observed at a large inclination angle ($i\gtrsim60^{\circ}$). The derived circumstellar disk size shows that the disk evolves from a configuration that prevents accretion onto the neutron star, to one that allows only moderate accretion. This is in agreement with the contemporary observed X-ray activity. Our results are interpreted within the context of inefficient tidal truncation of the circumstellar disk, as expected for this source's binary configuration. We derived the H$β$-emitting region size, which results about half of the corresponding H$α$-emitting disk, and constrain the luminosity class of V850 Cen as III-V, consistent with the previously proposed class.}
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