EXTREME ORBITAL EVOLUTION FROM HIERARCHICAL SECULAR COUPLING OF TWO GIANT PLANETS
EXTREME ORBITAL EVOLUTION FROM HIERARCHICAL SECULAR COUPLING OF TWO GIANT PLANETS
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两颗巨行星分层长期耦合的极端轨道演化
DOI：
10.1088/0004-637x/779/2/166
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
F. Rasio
中科院分区：
文献类型：
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作者：
J. Teyssandier;S. Naoz;Ian Lizarraga;F. Rasio
在过去的二十年里，对系外行星的观测揭示了一类新的行星，其轨道周期为几天，即所谓的“热行星”。最近使用罗西特-麦克劳克林效应的测量显示，这些行星中有许多（约50%）是不对齐的;此外，有些（约15%）甚至是相对于恒星自转轴逆行的。受这些观测的启发，我们探索了在一个更宽的轨道上形成逆行轨道的可能性，逆行轨道由一个恒星-行星内部对与另一个巨行星或褐矮星组成。最近的研究表明，在这样一个系统中，内行星的轨道可以从逆行到逆行来回翻转，也可以达到极高的离心率。在这里，我们映射这些系统的动态结果的参数空间的重要部分。我们推导出强烈的约束外摄动（第三）的轨道配置，可能会导致形成的热彗星与错位或逆行轨道。我们只关注长期演化，忽略了其他动力学效应，如平均运动共振，以及所有耗散力。例如，如果一颗类木星的内行星最初在5 Au的近圆形轨道上运行，我们表明，如果有一颗质量更大（>2 MJ）的行星伴星（在距离内系统140 Au内），相互倾角>50°，离心率超过10.25，那么很可能会形成一颗偏离轨道的热木星。这与测试粒子近似形成了鲜明的对比，在测试粒子近似中，几乎垂直的配置仍然可以引起大偏心率的激发，但是内部类似于行星的行星翻转发生的可能性要小得多。我们得到的约束条件可以用来指导未来的观测，特别是在包含热木星的系统中寻找更遥远的同伴。
Observations of exoplanets over the last two decades have revealed a new class of Jupiter-size planets with orbital periods of a few days, the so-called “hot Jupiters.” Recent measurements using the Rossiter–McLaughlin effect have shown that many (∼50%) of these planets are misaligned; furthermore, some (∼15%) are even retrograde with respect to the stellar spin axis. Motivated by these observations, we explore the possibility of forming retrograde orbits in hierarchical triple configurations consisting of a star–planet inner pair with another giant planet, or brown dwarf, in a much wider orbit. Recently, it was shown that in such a system, the inner planet's orbit can flip back and forth from prograde to retrograde and can also reach extremely high eccentricities. Here we map a significant part of the parameter space of dynamical outcomes for these systems. We derive strong constraints on the orbital configurations for the outer perturber (the tertiary) that could lead to the formation of hot Jupiters with misaligned or retrograde orbits. We focus only on the secular evolution, neglecting other dynamical effects such as mean-motion resonances, as well as all dissipative forces. For example, with an inner Jupiter-like planet initially on a nearly circular orbit at 5 AU, we show that a misaligned hot Jupiter is likely to be formed in the presence of a more massive planetary companion (>2 MJ) within ∼140 AU of the inner system, with mutual inclination >50° and eccentricity above ∼0.25. This is in striking contrast to the test particle approximation, where an almost perpendicular configuration can still cause large-eccentricity excitations, but flips of an inner Jupiter-like planet are much less likely to occur. The constraints we derive can be used to guide future observations and, in particular, searches for more distant companions in systems containing a hot Jupiter.