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arXiv 0812.2475astro-ph
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行星系统HD69830的动力学模拟

Dynamical Simulations of the Planetary System HD69830

Matthew J. Payne, Eric B. Ford, Mark C. Wyatt, Mark Booth

摘要:

HD 69830的径向速度变化归因于三颗行星,以及红外辐射归因于一个温暖的碎片盘。以前的研究已经建立了行星迁移和质量增长(Alibert等人,2006年)以及温暖谷物补充(Wyatt等人,2007年)的模型。我们进行n体积分,以探讨这些模型的影响:1)激发行星偏心率,2)吸积和清除一个假定的星子盘,3)迁移后的星子轨道的分布,和4)的影响的起源的红外辐射。我们发现:i)无法解释观测到的行星偏心率(e~0.1)纯粹是迁移过程中行星扰动的结果,除非行星系统几乎是面对面的。ii)在我们的n体模拟中,行星上的星子吸积速率与半解析模型中假设的速率有很大不同,这表明人们不能用Alibert等人(2006)的简化方式成功地处理星子吸积。iii)微行星的偏心阻尼并不作为存在受激偏心盘的不可逾越的障碍:所有的模拟结果都表明,至少有25个地球质量的物质仍然束缚在约1-9 AU的区域内,即使在所有三颗行星都迁移通过该区域之后。iv)气体阻力对微行星进行大小排序,最大的天体优先占据最高偏心率和最长寿命的轨道。进一步的工作将需要了解这些偏心率分布是否足够高,以解释观测到的尘埃排放水平,尽管通过稳态碰撞演化的质量损失。[删节]

英文摘要:

HD 69830 exhibits radial velocity variations attributed to three planets as well as infrared emission attributed to a warm debris disk. Previous studies have developed models for the planet migration and mass growth (Alibert et al. 2006) and the replenishment of warm grains (Wyatt et al. 2007). We perform n-body integrations in order to explore the implications of these models for: 1) the excitation of planetary eccentricity, 2) the accretion and clearing of a putative planetesimal disk, 3) the distribution of planetesimal orbits following migration, and 4) the implications for the origin of the IR emission. We find that: i) It is not possible to explain the observed planetary eccentricities (e~0.1) purely as the result of planetary perturbations during migration unless the planetary system is nearly face-on. ii) The rate of accretion of planetesimals onto planets in our n-body simulations is significantly different to that assumed in the semi-analytic models, suggesting that one cannot successfully treat planetesimal accretion in the simplified manner of Alibert et al. (2006). iii) Eccentricity damping of planetesimals does not act as an insurmountable obstacle to the existence of an excited eccentric disk: All simulations result in at least 25 Earth-masses of material remaining bound in the region ~1-9 AU, even after all three planets have migrated through the region. iv) Gas drag works to size-sort the planetesimals, with the largest bodies preferentially occupying the highest eccentricity and longest-lived orbits. Further work will be required to understand whether these eccentricity distributions are high enough to explain the level of dust emission observed despite mass loss via steady state collisional evolution. [abridged]

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