arXiv 1810.085482018-10-19astro-ph.SR

年轻双星M矮星的旋转演化

The Rotational Evolution of Young, Binary M Dwarfs

John Stauffer, Luisa Rebull, Ann Marie Cody, Lynne Hillenbrand, Marc Pinsonneault, David Barrado, Jerome Bouvier, Trevor David

备注：: accepted by AJ
DOI：: 10.3847/1538-3881/aae9ec

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摘要：

我们分析了$\sim$ 800万年前的上天蝎座星协、$\sim$ 1.25亿年前的昴星团疏散星团和$\sim$ 7亿年前的毕星团和普雷塞普疏散星团中3,000多颗低质量恒星的K 2光变曲线，以确定恒星的自转速率。这些K2目标中的许多都显示出两个不同的周期，对于这些星团中质量最低的恒星来说，几乎所有具有两个周期的系统都是光度双星。最可能的解释是，我们正在检测这些双星的两个组成部分的旋转周期。我们探讨的两个组成部分的光度双星相对于彼此和非光度双星的旋转速率的演变。在上天蝎座和昂宿星团中，这些低质量双星的平均周期要短得多，而且它们之间的距离要比随机从M矮单星中抽取的周期近得多。在上天蝎座，这种差异与原始星周盘导致的红外过度的存在或不存在密切相关-单星人口包括许多具有盘的恒星，并且它们的旋转周期平均比相同质量的双星表亲明显更长。由Praesepe年龄，在旋转速率之间的差异的意义单一和二进制低质量的dMs是少得多，这表明角动量损失的风完全对流零年龄的主序星擦除记忆的旋转速率二分法的二进制和单一的非常低的质量的恒星在以后的年龄。

英文摘要：

We have analysed K2 light curves for more than 3,000 low mass stars in the $\sim$8 Myr old Upper Sco association, the $\sim$125 Myr age Pleiades open cluster and the $\sim$700 Myr old Hyades and Praesepe open clusters to determine stellar rotation rates. Many of these K2 targets show two distinct periods, and for the lowest mass stars in these clusters virtually all of these systems with two periods are photometric binaries. The most likely explanation is that we are detecting the rotation periods for both components of these binaries. We explore the evolution of the rotation rate in both components of photometric binaries relative to one another and to non-photometric binary stars. In Upper Sco and the Pleiades, these low mass binary stars have periods that are much shorter on average and much closer to each other than would be true if drawn at random from the M dwarf single stars. In Upper Sco, this difference correlates strongly with the presence or absence of infrared excesses due to primordial circumstellar disks -- the single star population includes many stars with disks, and their rotation periods are distinctively longer on average than their binary star cousins of the same mass. By Praesepe age, the significance of the difference in rotation rate between the single and binary low mass dMs is much less, suggesting that angular momentum loss from winds for fully-convective zero-age main sequence stars erases memory of the rotation rate dichotomy for binary and single very low mass stars at later ages.

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