Rotational and Candidate-Eclipsing-Binary Light Curves for Pre-Main-Sequence Stars in the Chamaeleon I Star-Forming Cloud
Rotational and Candidate-Eclipsing-Binary Light Curves for Pre-Main-Sequence Stars in the Chamaeleon I Star-Forming Cloud
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Chamaeleon I 恒星形成云中前主序星的旋转和候选食双星光曲线
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
L. Crause
中科院分区：
文献类型：
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作者：
W. Lawson;L. Crause
摘要本文介绍了变色龙区域十颗X射线低质量恒星的光度测量结果。我们观测到的恒星中有八颗是真正的前主序成员，它们是1200万年前的变色龙I恒星形成云。另外两颗恒星是年轻的，有高水平的相对X射线发射，但由于不协调的自行，它们可能不是星云的成员。在我们监测的六颗恒星中，检测到2.5-11.5 d的时间尺度的周期性变化，我们将其归因于恒星旋转和冷星斑的存在。另外两颗恒星，CHXR 20和CHXR 85，在可见光和近红外波段显示出巨大的振幅变化，是候选的食双星。与1800万年前的变色龙η星团中的低质量恒星的旋转性质相比，我们发现较老的变色龙η恒星比年轻的变色龙I恒星具有高出数倍的表面比角动量。角动量在2000万年到800万年之间的明显增加可能是由于恒星演化过程中恒星内部结构的变化，或者是两个恒星形成区成员之间不同旋转历史的证据。
Abstract We present the results of a photometric survey for variability in ten X-ray-emitting low-mass stars in the Chamaeleon region. Eight of the stars we observed are bona fide pre-main-sequence members of the ∼2 Myr-old Chamaeleon I star-forming cloud. The other two stars are young with high levels of relative X-ray emission, but with discordant proper motions they are probable non-members of the cloud. In six of the stars we monitored, periodic variations on timescales of 2.5–11.5 d were detected, that we ascribe to stellar rotation and the presence of cool starspots. Two other stars, CHXR 20 and CHXR 85, show large amplitude variations at visual and near-infrared wavelengths and are candidate eclipsing binaries. Compared to the rotational properties of low-mass stars in the ≈8 Myr-old η Chamaeleontis cluster, we find that the older η Chamaeleontis stars have several times higher surface specific angular momentum than the younger Chamaeleon I stars. The apparent increase in angular momentum between ∼2 and 8 Myr might be due to changes in stellar internal structure as the stars evolve, or evidence for a different rotational history between members of the two star-forming regions.