Towards a Deterministic Model of Planetary Formation. Iii. Mass Distribution of Short-period Planets around Stars of Various Masses
Towards a Deterministic Model of Planetary Formation. Iii. Mass Distribution of Short-period Planets around Stars of Various Masses
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发表时间：
2005
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通讯作者：
S. Ida;D. Lin
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作者：
S. Ida;D. Lin
最近在GJ436附近发现的一颗海王星质量的行星的起源对目前的行星形成理论提出了挑战。基于序贯吸积假说和间隙形成和轨道迁移的标准理论，我们表明，在M矮星周围，接近海王星质量的冰巨行星可能是相对常见的，而接近海王星质量的气体巨行星相对罕见。近距离行星的质量分布通常有两个峰值，大约是海王星质量和木星质量。质量较低的峰值是M矮星的最大频率。在更大质量的太阳型恒星（G矮星）周围，更高质量的峰值更加明显。这是因为行星倾向于在G矮星周围完全吸积气体后进行II型迁移，而它们倾向于比M恒星周围的气体吸积迁移更快。在G矮星周围也可能存在质量接近海王星的行星，虽然它们往往主要由硅酸盐和铁核心组成，并且它们的频率预计要比M矮星周围的海王星质量行星和G矮星周围的气体巨星小得多。我们还表明，行星的迁移条件，由于其潮汐相互作用与磁盘和恒星质量的依赖，磁盘质量分布可以校准的质量分布的短周期行星周围的主恒星具有不同的质量。
The origin of a recently discovered close-in Neptune-mass planet around GJ436 poses a challenge to the current theories of planet formation. Based on the sequential accretion hypothesis and the standard theory of gap formation and orbital migration, we show that around M dwarf stars, close-in Neptune-mass ice-giant planets may be relatively common, while close-in Jupiter-mass gas-giant planets are relatively rare. The mass distribution of close-in planets generally has two peaks at about Neptune mass and Jupiter mass. The lower-mass peak takes the maximum frequency for M dwarfs. Around more massive solar-type stars (G dwarfs), the higher-mass peak is much more pronounced. These are because planets tend to undergo type II migration after fully accreting gas around G dwarfs while they tend to migrate faster than gas accretion around M stars. Close-in Neptune-mass planets may also exist around G dwarfs, though they tend to be mostly composed of silicates and iron cores and their frequency is expected to be much smaller than that of Neptune-mass planets around M dwarfs and that of gas giants around G dwarfs. We also show that the conditions for planets' migration due to their tidal interaction with the disk and the stellar-mass dependence in the disk-mass distribution can be calibrated by the mass distribution of short-period planets around host stars with various masses.