Title: A star-by-star correspondence between X-ray activity and rotation in the young open cluster NGC 2516 with eROSITA Show Chinese title

Title: X射线活动与旋转在年轻开放星团NGC 2516中的逐星对应关系与eROSITA

Abstract: The coronal soft X-ray emission of cool stars, especially when taken in combination with their measured rotation periods, offers insights into their levels of magnetic activity and related transitions. We study the X-ray properties of low-mass members of the open cluster NGC 2516 to explicate their detailed dependencies on mass and rotation. We analysed the pointed SRG/eROSITA satellite observations of NGC 2516 obtained during the calibration and performance verification phase of the mission. We found 1561 X-ray sources within the field of view and related 1007 of them to their optical stellar counterparts, including 655 members of NGC 2516 (433 with rotation periods). We combined these detections with auxiliary optical data to facilitate their interpretation. Furthermore, we extracted X-ray spectra for all sources and fit two-component APEC models to them. To aid the analysis, we grouped stars with similar mass and rotational properties together, which allowed us to investigate the influence of rotation on various X-ray properties. The colour-activity diagram of NGC 2516 displays a general increase in the fractional X-ray luminosity with spectral type change from F through G and K to M-type. However, the behaviour of K-type stars, representing the ones that best sample the fast-to-slow rotational transition, is more complex, with both increased and decreased X-ray emission relative to G-type stars for fast and slow rotators, respectively. The rotation-activity diagram is analogous, with an identifiable desaturated group of X-ray emitters that corresponds to stars in the rotational gap between the fast and slow rotator sequences. We prefer to describe the normalised X-ray emission for all cluster stars as declining logarithmically with Rossby number over those using broken power laws. Coronal temperatures appear to be largely independent of mass or rotation. (abridged) Show Chinese abstract

Abstract: 日冕软X射线发射的冷却恒星，特别是当与它们测量的自转周期结合时，可以提供关于其磁活动水平及相关转变的见解。 我们研究了疏散星团NGC 2516中低质量成员的X射线特性，以阐明它们对质量和自转的详细依赖关系。 我们分析了在任务校准和性能验证阶段获得的NGC 2516的定点SRG/eROSITA卫星观测数据。 我们在视场内发现了1561个X射线源，并将其中的1007个与它们的光学恒星对应体相关联，包括655个NGC 2516的成员（433个具有自转周期）。 我们将这些检测结果与辅助的光学数据相结合，以促进它们的解释。 此外，我们提取了所有源的X射线光谱，并对它们拟合了两组分APEC模型。 为了帮助分析，我们将具有相似质量和旋转特性的恒星分组在一起，这使我们能够研究自转对各种X射线特性的影响。 NGC 2516的颜色-活动图显示，随着光谱类型从F型经过G型和K型到M型变化，X射线光度的比例普遍增加。 然而，K型恒星的行为更为复杂，它们代表了最能采样快速到慢速自转过渡的恒星，相对于G型恒星，快速自转者表现出更高的X射线发射，而慢速自转者则表现出更低的X射线发射。 旋转-活动图类似，有一个可识别的X射线发射器去饱和群体，对应于快速和慢速自转序列之间的自转间隙中的恒星。 我们更倾向于描述所有星团恒星的归一化X射线发射随罗斯比数的对数下降，而不是使用断续幂律。 日冕温度似乎在很大程度上与质量和自转无关。 （摘要）