The stellar content of wide-angle soft X-ray sky surveys

在今后两年内，盖亚卫星（2013年12月发射）目前收集的数据将可供广大天文学使用。这些数据可能会彻底改变天文学，也会改变恒星X射线天文学。盖亚数据的发布特别意味着一个完整的恒星目录包含三个波段的精确测光（两个在宽带，一个在窄带）将成为可用的，而且，精确的视差和自行信息将成为基本上所有较亮的恒星。就恒星X射线天文学而言，这意味着在ROSAT全天巡天、XMM-牛顿回转巡天和未来的eROSITA全天巡天框架内已经/将要探测到的基本上所有恒星（将于2017-2021年之间进行）将精确地知道松弛度，因此距离，从而允许X射线发光度的计算精确到大约10%或更好。这是第一次，包含成百上千颗X射线亮星的大样本将变得可用，从而可以评估与X射线源计数的任何定量评估相关的分布函数的高光度尾部。此外，在一般领域对年轻恒星的系统研究也将成为可能，因为它们已经从诞生区分散开来。在这项资助申请的框架内，我们要求支持开展一项努力，利用现有的高精度恒星目录和即将到来的盖亚数据，在光度学和光度计方面提取ROSAT全天巡天和XMM-牛顿回转巡天的恒星内容。有了这些输入，我们期望以高精度和可靠性识别这些X射线巡天中的恒星种群，并将使用结果来计算精确的X射线光度函数，活动恒星的空间密度，并识别该领域中的后T金牛座年轻恒星种群。

Within the next two years the data currently collected by the Gaia satellite (launched in December 2013) will become available for astronomical usage at large. This data is likely to revolutionise astronomy at large and also stellar X-ray astronomy. The Gaia data release specifically implies that a complete stellar catalog containing precise photometry in three bands (two in broad band, one in a narrow band) will become available, and, furthermore, precise parallax and proper motion information will become available for essentially all of the brighter stars. As far as stellar X-ray astronomy is concerned, this implies that basically all stars that have been/will be detected in the framework of the ROSAT all-sky survey, the XMM-Newton slew survey and the future eROSITA all-sky survey (to be conducted between 2017-2021) will have precisely known parallaxes and hence distances, thus allowing the computation of X-ray luminosities accurate to approximately 10% or better. For the first time large samples containing hundreds and thousands of X-ray bright stars will become available allowing an assessment of the high-luminosity tail of the distribution functions that is relevant for any quantitative assessment of the X-ray source counts. Furthermore, systematic studies of young stars in the general field will become possible, where they have dispersed from the birth regions. In the framework of this funding application we ask for support to carry out an effort to extract the stellar content of the ROSAT all-sky survey and the XMM-Newton slew survey using existing high-precision stellar catalogs and the upcoming Gaia data in terms of photometry and parallaxes. With these inputs we expect to identify the stellar population in these X-ray surveys with high accuracy and reliability and will use the results to compute accurate X-ray luminosity functions, space densities of active stars and identify the post T Tauri population of young stars in the field.