Sco-Cen OB星协的X射线观测：eROSITA揭示的低质量恒星星族
X-raying the Sco-Cen OB association: The low-mass stellar population revealed by eROSITA
摘要：
我们提出了第一次X射线全天巡天（eRASS 1）的结果进行的eROSITA仪器上的光谱伦琴伽马（SRG）天文台的Sco-Cen OB协会。Bona fide Sco-Cen成员星很年轻，因此预计会在饱和水平发射X射线。eRASS 1的灵敏度极限使这些恒星可以探测到太阳质量的十分之一。通过将eRASS 1源目录与Gaia EDR 3目录进行交叉相关，我们得到了恒星的完整识别（即，日冕）源的内容，特别是第一次获得了探测到的恒星X射线源的三维视图。把注意力集中在低质量的星群上，并把以这种方式确定的光学对应物放在色星等图中，我们就可以从探测到的X射线源中分离出年轻的恒星，并获得各种Sco-Cen星群的年龄估计。联合分析的2D和3D空间运动，后者只适用于一个较小的子集检测到的恒星X射线源，揭示了选定的人口的空间运动显示出高度的平行性，但也有一个额外的人口的年轻，X射线发射和基本上共空间的恒星，似乎在速度空间更分散。其性质目前尚不清楚。我们认为，与我们的程序，几乎整个恒星的天蝎座-岑星协内容的识别将成为可能，一旦最终的盖亚和eROSITA目录可在本十年结束。此外，我们质疑任何源人口分类方案，依赖于纯粹的运动学选择标准。
英文摘要：
We present the results of the first X-ray all-sky survey (eRASS1) performed by the eROSITA instrument on board the Spectrum-Roentgen-Gamma (SRG) observatory of the Sco-Cen OB association. Bona fide Sco-Cen member stars are young and are therefore expected to emit X-rays at the saturation level. The sensitivity limit of eRASS1 makes these stars detectable down to about a tenth of a solar mass. By cross-correlating the eRASS1 source catalog with the Gaia EDR3 catalog, we arrive at a complete identification of the stellar (i.e., coronal) source content of eROSITA\ in the Sco-Cen association, and in particular obtain for the first time a 3D view of the detected stellar X-ray sources. Focusing on the low-mass population and placing the optical counterparts identified in this way in a color-magnitude diagram, we can isolate the young stars out of the detected X-ray sources and obtain age estimates of the various Sco-Cen populations. A joint analysis of the 2D and 3D space motions, the latter being available only for a smaller subset of the detected stellar X-ray sources, reveals that the space motions of the selected population show a high degree of parallelism, but there is also an additional population of young, X-ray emitting and essentially cospatial stars that appears to be more diffuse in velocity space. Its nature is currently unclear. We argue that with our procedures, an identification of almost the whole stellar content of the Sco-Cen association will become possible once the final Gaia and eROSITA catalogs are available by the end of this decade. We furthermore call into question any source population classification scheme that relies on purely kinematic selection criteria.
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