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arXiv 1806.07892astro-ph.EPastro-ph.SR
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摇晃的恒星:有外部伴星的热和暖类星体对恒星倾角的共振激发

Teetering Stars: Resonant Excitation of Stellar Obliquities by Hot and Warm Jupiters with External Companions

Kassandra R. Anderson, Dong Lai

摘要:

热木星系统中的恒星自旋-轨道不对准(不对准)已被广泛探测。这样的不稳定性可能揭示热木星动力学历史的线索。对产生偏心的常见解释包括高偏心率迁移和原始磁盘未对准。本文研究了另一种机制,产生恒星自旋轨道错位系统托管一个接近的行星与外部,适度倾斜的同伴。当恒星自转轴的进动率(由内行星驱动)变得与内行星的节点进动率(由伴星驱动)相当时,可能会由于长期共振而激发自旋轨道不对准。由于主恒星通过磁制动的自旋下降,这种共振可能在恒星的主序星寿命期间实现,对于广泛的行星质量和轨道结构。倾斜激励伴随着内行星和扰动之间的相互倾斜的减少,因此可以消除高倾斜。对于热彗星来说,恒星的自转轴与轨道轴有很强的耦合,而被巨行星伴星激发的彗星需要一个很强的扰动,通常位于1-2天文单位内。对于温暖的类星体,自旋和轨道轴的耦合较弱,而对于遥远的巨行星摄动(在几个到几十个天文单位),可能会达到共振。由于暖木星有很高的出现率,遥远的行星伴星具有适当的共振共振激发性质,因此在暖木星系统中,恒星的共振激发可能很常见,特别是对于那些绕着经历了显著自旋下降的冷恒星运行的暖木星。

英文摘要:

Stellar spin-orbit misalignments (obliquities) in hot Jupiter systems have been extensively probed. Such obliquities may reveal clues about hot Jupiter dynamical histories. Common explanations for generating obliquities include high-eccentricity migration and primordial disk misalignment. This paper investigates another mechanism for producing stellar spin-orbit misalignments in systems hosting a close-in planet with an external, modestly inclined companion. Spin-orbit misalignment may be excited due to a secular resonance, occurring when the precession rate of the stellar spin axis (driven by the inner planet) becomes comparable to the nodal precession rate of the inner planet (driven by the companion). Due to the spin-down of the host star via magnetic braking, this resonance may be achieved during the star's main-sequence lifetime for a wide range of planet masses and orbital architectures. Obliquity excitation is accompanied by a decrease in mutual inclination between the inner planet and perturber, and can thus erase high inclinations. For hot Jupiters, the stellar spin axis is strongly coupled to the orbital axis, and obliquity excitation by a giant planet companion requires a strong perturber, usually located within 1-2 AU. For warm Jupiters, the spin and orbital axes are more weakly coupled, and the resonance may be achieved for distant giant planet perturbers (at several to tens of AU). Since warm Jupiters have a high occurrence rate of distant planetary companions with appropriate properties for resonant obliquity excitation, stellar obliquities in warm Jupiter systems may be common, particularly for warm Jupiters orbiting cool stars that have undergone significant spin-down.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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