arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新，休息一下吧，周末愉快~~
arXiv 2005.09179astro-ph.SR
收藏

8个快速旋转的X射线明亮的FK彗星候选者的光谱偏振跟踪

Spectropolarimetric follow-up of 8 rapidly rotating, X-ray bright FK Comae candidates

James Sikora, Jason Rowe, Steve Howell, Elena Mason, Gregg A. Wade

备注：
15 pages, 12 figures. Accepted for publication in MNRAS
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

我们对演化的、快速旋转的、磁性活跃的、显然是单一的FK Comae恒星的理解受到了它们的极端稀有性的阻碍：除了FK Comae本身之外，目前只有两颗恒星被认为是这类恒星的成员。最近，在\emph{Kepler-Swift}活动星系和恒星（KSwAGS）巡天的背景下，确定了20多颗候选FK后发座型恒星的样本。我们对其中8个候选项使用ESPaDOnS@CFHT获得的高分辨率斯托克斯$V$观测结果进行了分析。我们发现，这些目标都不能被认为是FK彗星类的成员，主要是基于他们推断的旋转速度和检测光谱二进制同伴。然而，2个目标显示出磁活动的证据，并具有异常高的投影旋转速度（$v\sin{i}$）相对于与类似演化状态的恒星相关的典型值。EPIC 210426551有一颗$v\sin{i}=209\,{\rm km\,s}^{-1}$，估计质量为$1.07\,M_\odot$，部分基于它的金属丰度${\rm [M/H]}=-0.4$，它是一颗演化的主序星或前主序星。KIC 7732964的质量为$0.84\,M_\odot$，位于红巨星分支的底部附近，并显示出$v\sin{i}=23\,{\rm km\,s}^{-1}$。我们发现，这两个对象有类似的特点FK COM（虽然不那么极端），他们的快速旋转可能是不一致的预测一个单一的恒星演化历史。为了更好地限制它们的进化状态以及它们是否有短周期的双星伴星，还需要进行额外的观测。

英文摘要：

Our understanding of the evolved, rapidly rotating, magnetically active, and apparently single FK Comae stars is significantly hindered by their extreme rarity: only two stars in addition to FK Com itself are currently considered to be members of this class. Recently, a sample of more than 20 candidate FK Comae type stars was identified within the context of the \emph{Kepler-Swift} Active Galaxies and Stars (KSwAGS) survey. We present an analysis of high-resolution Stokes $V$ observations obtained using ESPaDOnS@CFHT for 8 of these candidates. We found that none of these targets can be considered members of the FK Comae class based primarily on their inferred rotational velocities and on the detection of spectroscopic binary companions. However, 2 targets show evidence of magnetic activity and have anomalously high projected rotational velocities ($v\sin{i}$) relative to typical values associated with stars of similar evolutionary states. EPIC 210426551 has a $v\sin{i}=209\,{\rm km\,s}^{-1}$, an estimated mass of $1.07\,M_\odot$, and, based in part on its derived metallicity of ${\rm [M/H]}=-0.4$, it is either an evolved main sequence (MS) star or a pre-MS star. KIC 7732964 has a mass of $0.84\,M_\odot$, lies near the base of the red giant branch, and exhibits a $v\sin{i}=23\,{\rm km\,s}^{-1}$. We find that these two objects have similar characteristics to FK Com (albeit less extreme) and that their rapid rotation may be inconsistent with that predicted for a single star evolutionary history. Additional observations are necessary in order to better constrain their evolutionary states and whether they have short-period binary companions.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑