论文标题
通过碟片不稳定性，M矮人的行星形成：碎裂条件和原性特性
Planet formation around M dwarfs via disc instability: Fragmentation conditions and protoplanet properties
论文作者
论文摘要
背景：大约30％的观察到的系外行星轨道列恒星是气体巨头，比木星更大。这些行星是通过光盘不稳定性组成的主要候选者。目的：我们要确定围绕M矮人的光盘碎片的条件以及由光盘不稳定性形成的行星的特性。方法：我们对M矮蛋白盘进行了流体动力学模拟，以确定引力碎片发生所需的最小椎间盘质量。考虑了不同的恒星质量，圆盘半径和金属性。每个原始圆盘的质量稳步增加，直到圆盘碎裂并形成原子星状。结果：我们发现，碎片化发生需要圆盘与明星质量比在$ \ sim 0.3 $和$ \ sim 0.6 $之间。圆盘片段随着恒星质量和圆盘尺寸增加的最小质量。金属性不会显着影响最小盘碎片质量，但高金属性可能会抑制碎片。距离寄主恒星$ \ sim50 $ au的距离很快（在几千年之内）形成原始星团，它们最初非常热；他们的中心的温度类似于核心积聚（高达12,000K）的行星周围的积聚冲击中预期的温度。这些行星（例如质量和轨道半径）的最终特性是通过长期的椎间盘或行星线路相互作用确定的。结论：圆盘不稳定性是一种在M矮人周围形成气体巨星行星的合理方法，前提是在其成立的初始阶段，圆盘的宿主恒星质量至少为30％。需要对非常年轻的M矮人围绕大型M矮圆盘或行星进行的未来观察，以确立圆盘不稳定性在低质量恒星周围形成行星的重要性。
Context: Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive than Jupiter. These planets are prime candidates for formation by disc instability. Aims: We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planets that are formed by disc instability. Methods: We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities were considered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet was formed. Results: We find that a disc-to-star mass ratio between $\sim 0.3$ and $\sim 0.6$ is required for fragmentation to happen. The minimum mass at which a disc fragments increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets form quickly (within a few thousand years) at distances around $\sim50$ AU from the host star, and they are initially very hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formed by core accretion (up to 12,000K). The final properties of these planets (e.g. mass and orbital radius) are determined through long-term disc-planet or planet-planet interactions. Conclusions: Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs have at least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability for planet formation around low-mass stars.
