Title: Tidal Decay and Stable Roche-Lobe Overflow of Short-Period Gaseous Exoplanets Show Chinese title

Title: 短周期气态系外行星的潮汐衰减与稳定罗氏瓣溢出

Abstract: Many gaseous exoplanets in short-period orbits are on the verge or are in the process of Roche-lobe overflow (RLO). Moreover, orbital stability analysis shows tides can drive many hot Jupiters to spiral inevitably toward their host stars. Thus, the coupled processes of orbital evolution and RLO likely shape the observed distribution of close-in exoplanets and may even be responsible for producing some of the short-period rocky planets. However, the exact outcome for an overflowing planet depends on its internal response to mass loss, and the accompanying orbital evolution can act to enhance or inhibit RLO. In this study, we apply the fully-featured and robust Modules for Experiments in Stellar Astrophysics (MESA) suite to model RLO of short-period gaseous planets. We show that, although the detailed evolution may depend on several properties of the planetary system, it is largely determined by the core mass of the overflowing gas giant. In particular, we find that the orbital expansion that accompanies RLO often stops and reverses at a specific maximum period that depends on the core mass. We suggest that RLO may often strand the remnant of a gas giant near this orbital period, which provides an observational prediction that can corroborate the hypothesis that short-period gas giants undergo RLO. We conduct a preliminary comparison of this prediction to the observed population of small, short-period planets and find some planets in orbits that may be consistent with this picture. To the extent that we can establish some short-period planets are indeed the remnants of gas giants, that population can elucidate the properties of gas giant cores, the properties of which remain largely unconstrained. Show Chinese abstract

Abstract: 许多处于短周期轨道上的气态系外行星正处于洛希瓣溢出（RLO）的边缘或正在经历RLO过程。此外，轨道稳定性分析表明，潮汐作用可以驱动许多热木星不可避免地螺旋向其宿主恒星靠近。因此，轨道演化与RLO的耦合过程可能塑造了观测到的近距离系外行星分布，甚至可能是产生一些短周期岩石行星的原因。然而，溢出行星的最终结果取决于其对质量损失的内部响应，伴随的轨道演化可能会增强或抑制RLO。在本研究中，我们应用功能齐全且稳健的恒星天体物理实验模块（MESA）套件来模拟短周期气态行星的RLO。我们表明，尽管详细演化可能取决于行星系统的几个特性，但主要由溢出气体巨行星的核心质量决定。特别是，我们发现伴随RLO发生的轨道扩张通常会在一个特定的最大周期处停止并反转，该周期取决于核心质量。我们认为，RLO可能经常将气体巨行星的残余物留在这一轨道周期附近，这提供了一个观测预测，可用于验证短周期气体巨行星经历RLO的假设。我们对该预测与小而短周期行星的观测群体进行了初步比较，发现一些行星的轨道可能与此图景一致。在我们能够确定一些短周期行星确实是气体巨行星的残余物的程度上，该群体可以阐明气体巨行星核心的特性，这些特性目前仍 largely unconstrained。