论文标题
8迅速旋转，X射线明亮的FK Comae候选者的光谱极限随访
Spectropolarimetric follow-up of 8 rapidly rotating, X-ray bright FK Comae candidates
论文作者
论文摘要
我们对进化，快速旋转，磁性和显然单一FK COMAE星星的理解受到了极高的稀有性的严重阻碍：目前，除了FK COM本身之外，只有两颗恒星被认为是该类别的成员。最近，在\ emph {kepler-swift}活动星系和恒星（KSWAGS）调查的背景下确定了20多个候选FK Comae类型星的样本。我们对使用espadons@cfht获得的8个候选人获得的高分辨率Stokes $ V $观测值进行了分析。我们发现，这些目标都不能被视为FK COMAE类的成员，这主要基于其推断的旋转速度和检测光谱二进制伴侣。但是，相对于与类似进化状态相关的典型值，2个目标显示了磁性活性的证据，并且具有异常高的投影旋转速度（$ v \ sin {i} $）。 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)明星或前MS明星。 KIC 7732964的质量为$ 0.84 \，m_ \ odot $，位于红色巨型分支的底部附近，并展示了$ v \ sin {i} = 23 \，{\ rm km \，s}^，s}^{ - 1} $。我们发现，这两个对象具有与FK COM相似的特征（尽管极端不太极端），并且它们的快速旋转可能与单星进化史所预测的那样不一致。为了更好地限制其进化状态以及它们是否具有短期二元伴侣，需要进行其他观察。
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.
