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arXiv 2205.12971astro-ph.EPastro-ph.SR
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RV探测到的M矮星周围的行星：核心吸积模型的挑战

RV-detected planets around M dwarfs: Challenges for core accretion models

Martin Schlecker, Remo Burn, Silvia Sabotta, Antonia Seifert, Thomas Henning, Alexandre Emsenhuber, Christoph Mordasini, Sabine Reffert, Yutong Shan, Hubert Klahr

备注：
Accepted for publication in A&A. 19 pages, 9 figures
发表信息：
A&A 664, A180 (2022)
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摘要：

行星形成对原行星盘中的条件很敏感，已知原行星盘中的比例定律是恒星质量的函数。我们的目标是测试观察到的低质量恒星周围的行星人口是否可以用这些趋势来解释，或者是否需要单独的形成通道。我们解决这个问题，面对一个国家的最先进的行星人口合成模型与样本的行星周围的M矮星观测的HARPS和CARMENES径向速度（RV）调查。为了解释检测偏差，我们对实际RV数据进行了注入和检索实验，以产生我们模拟的行星核心吸积范例的合成观测结果。这些模拟强有力地产生了以前报道的高发生率的岩石行星周围的M矮星，并普遍同意其行星质量函数。相比之下，我们的模拟无法重现质量小于0.5个太阳质量的恒星周围的巨行星群。这可能表明，在质量最小的恒星周围存在着另一种形成巨行星的通道，这是目前核心吸积理论无法解释的。我们进一步发现恒星质量依赖于短周期行星的探测率。在我们的样本中，早期类型的恒星（$M_\star \gtrsim 0.4\, M_\odot$）周围缺乏近距离行星仍然无法用我们的模型解释，并表明不同光谱亚型的磁盘中存在不同的行星迁移障碍。这两种差异都可以归因于我们对新生M矮星系统中行星迁移的理解存在差距。他们强调了不同光谱亚型的年轻恒星周围的不同条件，以及在研究行星形成时考虑这些差异的重要性。

英文摘要：

Planet formation is sensitive to the conditions in protoplanetary disks, for which scaling laws as a function of stellar mass are known. We aim to test whether the observed population of planets around low-mass stars can be explained by these trends, or if separate formation channels are needed. We address this question by confronting a state-of-the-art planet population synthesis model with a sample of planets around M dwarfs observed by the HARPS and CARMENES radial velocity (RV) surveys. To account for detection biases, we performed injection and retrieval experiments on the actual RV data to produce synthetic observations of planets that we simulated following the core accretion paradigm. These simulations robustly yield the previously reported high occurrence of rocky planets around M dwarfs and generally agree with their planetary mass function. In contrast, our simulations cannot reproduce a population of giant planets around stars less massive than 0.5 solar masses. This potentially indicates an alternative formation channel for giant planets around the least massive stars that cannot be explained with current core accretion theories. We further find a stellar mass dependency in the detection rate of short-period planets. A lack of close-in planets around the earlier-type stars ($M_\star \gtrsim 0.4\, M_\odot$) in our sample remains unexplained by our model and indicates dissimilar planet migration barriers in disks of different spectral subtypes. Both discrepancies can be attributed to gaps in our understanding of planet migration in nascent M dwarf systems. They underline the different conditions around young stars of different spectral subtypes, and the importance of taking these differences into account when studying planet formation.

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