从ROSAT全天巡天和斯隆数字巡天识别的X射线发射星
X-Ray-Emitting Stars Identified from the ROSAT All-Sky Survey and the Sloan Digital Sky Survey
摘要：
ROSAT全天巡天（RASS）是第一次对整个天空进行成像X射线巡天。虽然X射线源对应物的范围从遥远的类星体到附近的M矮星，但RASS数据本身往往不足以确定X射线源的性质。因此，需要大规模的后续程序来构建已知X射线发射器的样品。我们使用斯隆数字巡天（SDSS）产生的光学数据，以确定709恒星X射线发射器编目的RASS和属于SDSS数据发布1足迹。其中大部分是明亮的恒星，其日冕X射线发射不适合SDSS光谱学，SDSS光谱学是为较暗的物体（g > 15等）设计的。相反，我们使用SDSS测光，与2微米全天巡天和其他目录的相关性，以及来自Apache Point天文台3.5米望远镜的光谱学来识别这些恒星X射线对应物。我们的707个X射线发射F、G、K和M星的样本是此类恒星中最大的X射线选择样本之一。我们使用适合于主序星上的矮星的光度视差关系推导出这些恒星的距离，并使用这些距离计算LX。我们还确定了一个以前未知的激变变量（CV）作为RASS对应。另外，我们使用相关的RASS和SDSS光谱目录的CV和白矮星（WD）的研究这些罕见的X射线发射恒星的性质。我们检查之间的关系（fX/fg）和46 X射线发射CV的Hbeta发射线的等效宽度，并讨论了基于这些数量的子集的暂定分类。我们确定了17个新的X射线发射DA（氢）WD，其中三个是新确定的WD。（节略）
英文摘要：
The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. While X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient to determine the nature of an X-ray source. As a result, large-scale follow-up programs are required to construct samples of known X-ray emitters. We use optical data produced by the Sloan Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters cataloged in the RASS and falling within the SDSS Data Release 1 footprint. Most of these are bright stars with coronal X-ray emission unsuitable for SDSS spectroscopy, which is designed for fainter objects (g > 15 mag). Instead, we use SDSS photometry, correlations with the Two Micron All Sky Survey and other catalogs, and spectroscopy from the Apache Point Observatory 3.5 m telescope to identify these stellar X-ray counterparts. Our sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest X-ray-selected samples of such stars. We derive distances to these stars using photometric parallax relations appropriate for dwarfs on the main sequence, and use these distances to calculate LX. We also identify a previously unknown cataclysmic variable (CV) as a RASS counterpart. Separately, we use correlations of the RASS and the SDSS spectroscopic catalogs of CVs and white dwarfs (WDs) to study the properties of these rarer X-ray-emitting stars. We examine the relationship between (fX/fg) and the equivalent width of the Hbeta emission line for 46 X-ray-emitting CVs and discuss tentative classifications for a subset based on these quantities. We identify 17 new X-ray-emitting DA (hydrogen) WDs, of which three are newly identified WDs. (abridged)
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