野生系外行星系统K2-312=HD 80653的精确参数、形成与动力学稳定性
Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312=HD 80653
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中文总结 AI 辅助
研究野生系外行星系统K2-312=HD 80653，通过扩展径向速度监测及多方法联合分析细化轨道参数，模拟其形成和演化，发现K2-312c是高偏心冷木星，揭示行星-行星散射对其轨道影响及系统其他特性。
中文摘要 AI 辅助
拥有超短周期（USP）行星的行星系统结构是理解行星形成和迁移情景的关键诊断依据。这些系统中外围巨行星的存在对于检验动力学效应和卵石吸积理论尤为重要。我们对明亮恒星K2-312=HD80653进行了扩展径向速度（RV）监测，该恒星已知有一颗岩石质USP超级地球（$P_b = 0.720$天）。先前研究发现了长期趋势以及因外围高度偏心巨行星K2-312c产生的开普勒信号。我们旨在通过精确监测其近日点通过来细化K2-312c的轨道参数，并对该系统的形成和动力学演化进行建模。我们分析了一组237条HARPS-N高分辨率光谱，将先前文献的观测基线延长了近4年。我们对RVs与K2和TESS测光进行联合分析以细化两颗行星的历表和性质。为考虑恒星活动，我们将开普勒模型与高斯过程回归相结合。K2-312c是一颗位于宽轨道上的冷木星（轨道周期细化为$P_c = 871.32$天），最小质量为$M\sin(i)\sim5 M_{Jup}$，偏心率细化为$e_c \sim 0.85$。它是多行星系统中已知的最偏心冷木星之一，也是唯一一颗高度偏心且有USP行星伴星的。我们的模拟表明两颗巨行星之间的行星-行星散射可能将K2-312c驱动到当前的高偏心率， eject了另一颗巨行星，同时仍使K2-312b得以幸存。扩展的观测基线还使我们能够确定恒星自转周期和一个长活动周期，而新的K2约简提高了K2-312b二次日食探测的显著性。
英文摘要
The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. We present an extended radial velocity (RV) monitoring of the bright star K2-312=HD80653, known to host a rocky USP super-Earth ($P_b=0.720$d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. K2-312c is a cold Jupiter on a wide orbit (orbital period refined to $P_c=871.32$d), with a minimum mass of Msin(i)$\sim5 M_{Jup}$ and a refined eccentricity of $e_c \sim 0.85$. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b.
