AI 中文总结
本研究构建10秒差距内FGK型恒星的X射线星表，用RTV标度律解释日冕温度-光度关系，发现该关系离散度极小，仅三颗恒星为异常值。
AI 中文摘要
对恒星X射线辐射的全面测量，对理解恒星发电机、系外行星大气损失以及原行星盘蒸发具有重要意义。我们提供了一份10秒差距内FGK型主序星的X射线探测星表，该星表考虑了恒星多重性和探测器的光学加载效应。为构建该X射线星表，我们分析了SRG（Spectrum Roentgen Gamma）/eROSITA和XMM-Newton对FGK 10秒差距样本恒星的所有观测数据，并将该样本与ROSAT星表进行交叉匹配。我们对X射线光谱拟合热等离子体模型，以推导X射线流量和日冕温度。我们研究了日冕温度与X射线表面流量之间的关系，发现结果与不同类型太阳日冕磁结构所覆盖的范围一致。温度-光度关系的下限由蒙德尔极小期恒星HD 166620和另外三颗恒星定义，这三颗恒星的位置表明它们可能是蒙德尔极小期候选体。我们确定了XMM-Newton和eROSITA数据推导的温度-光度定律之间的系统差异，将其归因于两者不同的仪器响应函数。我们研究了短期耀斑和长期活动周期对日冕温度随X射线光度演化的影响。除三颗恒星外，整个样本的温度-光度关系表现出极小的离散度。针对观测到的kT-FX关系，太阳磁环的RTV标度律提供了自然解释。观测到的关系的小离散度表明，日冕磁环的长度与填充因子之间存在普遍标度关系。目前尚不清楚的原因导致三颗观测到的异常值偏离了磁环长度与填充因子之比的不变性。
英文摘要
A comprehensive measurement of stellar X-ray emission has important implications for our understanding of stellar dynamos, exoplanet atmosphere loss, and evaporation of protoplanetary disks. We present a catalogue of X-ray detections of the FGK-type main-sequence stars within 10 pc, which accounts for stellar multiplicity and optical loading of the detectors. To build the X-ray catalogue, we analysed all observations from SRG (Spectrum Roentgen Gamma)/eROSITA and XMM-Newton for stars in the FGK 10pc sample, and we cross-matched the sample with ROSAT catalogues. We fit thermal plasma models to the X-ray spectra to derive X-ray fluxes and coronal temperatures. We investigate the relation between coronal temperature and X-ray surface flux and find the result to be consistent with the ranges covered by different types of solar coronal magnetic structures. The lower end of the temperature-brightness relation is defined by the Maunder minimum star HD 166620 and three other stars whose positions identify them as possible Maunder minimum candidates. We identify systematic differences between the temperature-brightness law derived from XMM-Newton and eROSITA data that we attribute to their different instrumental response functions. We study the impact of both short-term flaring and long-term activity cycles on the evolution of coronal temperature along with X-ray brightness. With the exception of three stars, a remarkably small scatter is observed in the temperature-brightness relation across the whole sample. A natural explanation of the empirical kT-FX relation is provided by the RTV scaling law defined for solar magnetic loops. The small spread of the observed relation indicates a universal scaling between the length and the filling factor of coronal loops. The three observed outliers deviate from this invariance of the ratio of loop length to filling factor for an as of yet unknown reason.
Comments17 pages, 15 pages, Submitted to A&A
