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arXiv 2003.11590astro-ph.EP
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多行星系统中的Transit持续时间变化

Transit Duration Variations in Multi-Planet Systems

Aaron C. Boley, Christa Van Laerhoven, Agueda Paula Granados Contreras

摘要:

行星相对于观测者视线的轨道方位决定了凌日行星的弦长,即,一颗凌日行星在星盘上的投影距离。对于给定的圆形轨道,弦长决定了凌日持续时间。轨道倾角的变化,升交点的方向,或两者,可以改变这个弦长,从而导致过境时间变化(TDVs)。整个轨道倾角向量的变化甚至可以导致一个系统的行星脱离凌日或新凌日。我们用拉普拉斯-拉格朗日长期理论估计了100多个短周期行星系的最快节本征频率。最高本征频率是哪个系统应该显示最强TDV的指示器。我们进一步探讨了五个案例(TRAPPIST-1,开普勒-11,K2-138,开普勒-445和开普勒-334)使用直接N体模拟来表征可能的TDV,并探讨这些系统是否有可能存在行星。一系列的初始条件进行了探讨,与每个实现所观察到的过境一致。我们发现,百分之几十的多行星系统有足够快的本征频率,预计大TDVs十年的时间尺度。在直接整合的情况下,我们发现,去凌行星可能发生在十年的时间尺度和TDVs的10分钟每十年应该是常见的。

英文摘要:

A planet's orbital orientation relative to an observer's line of sight determines the chord length for a transiting planet, i.e., the projected distance a transiting planet travels across the stellar disc. For a given circular orbit, the chord length determines the transit duration. Changes in the orbital inclination, the direction of the ascending node, or both, can alter this chord length and thus result in transit duration variations (TDVs). Variation of the full orbital inclination vector can even lead to de-transiting or newly transiting planets for a system. We use Laplace-Lagrange secular theory to estimate the fastest nodal eigenfrequencies for over 100 short-period planetary systems. The highest eigenfrequency is an indicator of which systems should show the strongest TDVs. We further explore five cases (TRAPPIST-1, Kepler-11, K2-138, Kepler-445, and Kepler-334) using direct N-body simulations to characterize possible TDVs and to explore whether de-transiting planets could be possible for these systems. A range of initial conditions are explored, with each realization being consistent with the observed transits. We find that tens of percent of multiplanet systems have fast enough eigenfrequencies to expect large TDVs on decade timescales. Among the directly integrated cases, we find that de-transiting planets could occur on decade timescales and TDVs of 10 minutes per decade should be common.

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