在天球上部快速旋转的低质量WTT的开普勒同旋半径处的物质轨道云
Orbiting Clouds of Material at the Keplerian Co-Rotation Radius of Rapidly Rotating Low Mass WTTs in Upper Sco
摘要：
使用K2的数据，我们已经确定了23个非常低质量的成员的$ρ$ Oph和上天蝎座恒星形成区域具有周期性的光度变化不容易解释的完善的物理机制，如星点，食双星，或脉动。所有这些不寻常的恒星都是M型中晚期矮星，没有活跃吸积的证据，光度周期一般为$<$ 1天。通常，不寻常的光变曲线特征表现为狭窄的通量下降;当我们也有恒星黑子的旋转周期时，两个周期一致，这表明通量下降是由于以开普勒共同旋转半径绕恒星运行的物质。我们有时会在相位光变曲线形态中看到“状态变化”，其中$\sim$ 25%的波形在不到一天的时间尺度上改变形状;通常，“状态变化”发生在强烈耀斑之后。对于这些突然的光变曲线形态变化的恒星群，我们认为它们的通量下降最有可能是由温暖的日冕气体云的食引起的，类似于弹弓的折射率假设解释短暂的H $α$吸收功能在AB剑鱼座本身和其他快速旋转的晚型恒星。对于另一组恒星的周期稍长，我们发现短持续时间的流量骤降是高度可变的短期和长期的时间尺度上，一般不对称的流量骤降配置文件。我们相信，这些通量下降是由于微粒云可能与一个接近的行星或由最近的碰撞事件造成的。
英文摘要：
Using K2 data, we have identified 23 very low mass members of the $ρ$ Oph and Upper Scorpius star-forming region as having periodic photometric variability not easily explained by well-established physical mechanisms such as star spots, eclipsing binaries, or pulsation. All of these unusual stars are mid-to-late M dwarfs without evidence of active accretion, and with photometric periods generally $<$1 day. Often the unusual light curve signature takes the form of narrow flux dips; when we also have rotation periods from star spots, the two periods agree, suggesting that the flux dips are due to material orbiting the star at the Keplerian co-rotation radius. We sometimes see "state-changes" in the phased light curve morphologies where $\sim$25% of the waveform changes shape on timescales less than a day; often, the "state-change" takes place immediately after a strong flare. For the group of stars with these sudden light curve morphology shifts, we attribute their flux dips as most probably arising from eclipses of warm coronal gas clouds, analogous to the sling-shot prominences postulated to explain transient H$α$ absorption features in AB Doradus itself and other rapidly rotating late type stars. For another group of stars with somewhat longer periods, we find the short duration flux dips to be highly variable on both short and long timescales, with generally asymmetric flux dip profiles. We believe that these flux dips are due to particulate clouds possibly associated with a close-in planet or resulting from a recent collisional event.
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。
