Constraints on the spin evolution of young planetary-mass companions
Constraints on the spin evolution of young planetary-mass companions
复制标题
对年轻行星质量伴星自旋演化的限制
DOI：
10.1038/s41550-017-0325-8
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发表时间：
2017
期刊：
影响因子：
14.1
通讯作者：
B. Bowler
中科院分区：
文献类型：
--
作者：
M. Bryan;B. Benneke;H. Knutson;K. Batygin;B. Bowler
对年轻恒星形成区域的调查发现，年轻恒星周围的行星质量(<；13兆焦耳)伴星的数量正在增加。关于这些伴星是否像行星一样形成(也就是从星周盘中形成)2，或者它们是否代表恒星形成过程的低质量尾巴3，还有一个持续不断的争论。在这项研究中，我们利用高分辨率光谱测量了三个年轻的(2-300MYR)行星质量伴星的自转速度，并将这些测量与另外两个伴星的已公布的自转速度结合起来，4，5以提供这些天体的自旋分布的图像。我们将这个分布与6颗质量为 <；20MJup的棕矮星的互补自转速度测量进行了比较，结果表明这些分布是不可区分的。这表明这两个种群要么是通过相同的机制形成的，要么是调节旋转速度的过程独立于形成机制。我们发现，这两个种群的轮换速度都远远低于它们的分裂速度，并且在吸积结束后的最初数亿年里不会显著进化。这表明，自转速度是在吸积的后期阶段设定的，可能是通过与环行星盘的相互作用来设定的。这一结果对于我们理解年轻行星质量天体的角动量演化过程，以及行星质量体系中气体吸积和盘状耦合的物理过程具有重要的意义。类似的物理过程调节着气态巨行星和行星质量棕矮星的角动量。这些过程主要在行星演化的早期阶段活跃，因为在第一次2-300Myr之后，自转速度不会改变。
Surveys of young star-forming regions have discovered a growing population of planetary-mass (<13 MJup) companions around young stars1. There is an ongoing debate as to whether these companions formed like planets (that is, from the circumstellar disk)2, or if they represent the low-mass tail of the star-formation process3. In this study, we utilize high-resolution spectroscopy to measure rotation rates of three young (2–300 Myr) planetary-mass companions and combine these measurements with published rotation rates for two additional companions4,5 to provide a picture of the spin distribution of these objects. We compare this distribution to complementary rotation-rate measurements for six brown dwarfs with masses <20 MJup, and show that these distributions are indistinguishable. This suggests that either these two populations formed via the same mechanism, or that processes regulating rotation rates are independent of formation mechanism. We find that rotation rates for both populations are well below their break-up velocities and do not evolve significantly during the first few hundred million years after the end of accretion. This suggests that rotation rates are set during the late stages of accretion, possibly by interactions with a circumplanetary disk. This result has important implications for our understanding of the processes regulating the angular momentum evolution of young planetary-mass objects, and of the physics of gas accretion and disk coupling in the planetary-mass regime.Similar physical processes regulate the angular momentum of gas-giant planets and planetary-mass brown dwarfs. These processes are active mostly during the early phase of planetary evolution as rotation rates do not change after the first 2–300 Myr.