论文标题
南部超快速旋转低质量星的苔丝观察
TESS observations of southern ultra fast rotating low mass stars
论文作者
论文摘要
在我们先前使用苔丝对低质量恒星的研究中，我们发现了少数在<1 d期间显示的定期调制，但也没有表现出燃烧活动。在这里，我们介绍了在南方半球中对超快速旋转器（UFR）进行系统搜索的结果，在2分钟的节奏中与苔丝一起观察到。使用Gaia DR2的数据，我们获得了接近下主序列的13,000颗恒星的样本。其中，我们识别出位于较低主序列的609颗恒星，并具有周期性调制<1 d。显示耀斑的恒星的比例在<0.2 d的周期时似乎显着下降。如果周期是旋转速率的标志，那将是一个惊喜，因为预计更快的旋转器将具有更强的磁场，因此产生更多的耀斑。我们探讨了我们发现的可能原因：耀斑不活跃的恒星是二进制的成员，在这种情况下，随着二元轨道分离的降低，由于二元轨道分离的降低，恒星的旋转速率可能会增加，或者由于随时间的推移而减少了角度动量，或者这种增强的发射发生在苔丝通过以外的蓝色波长处。这些耀斑不活跃星的蓝色/紫外线波长处的随访光谱和耀斑监测需要解决此问题。
In our previous study of low mass stars using TESS, we found a handful which show a periodic modulation on a period <1 d but also displayed no flaring activity. Here we present the results of a systematic search for Ultra Fast Rotators (UFRs) in the southern ecliptic hemisphere which were observed in 2 min cadence with TESS. Using data from Gaia DR2, we obtain a sample of over 13,000 stars close to the lower main sequence. Of these, we identify 609 stars which lie on the lower main sequence and have a periodic modulation <1 d. The fraction of stars which show flares appears to drop significantly at periods <0.2 d. If the periods are a signature of the rotation rate, this would be a surprise, since faster rotators would be expected to have a stronger magnetic field and, therefore, produce more flares. We explore possible reasons for our finding: the flare inactive stars are members of binaries, in which case the stars rotation rate could have increased as the binary orbital separation reduced due to angular momentum loss over time, or that enhanced emission occurs at blue wavelengths beyond the pass band of TESS. Follow-up spectroscopy and flare monitoring at blue/ultraviolet wavelengths of these flare inactive stars are required to resolve this question.
