Resonant sub-Neptunes are puffier,Astronomy & Astrophysics

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Resonant sub-Neptunes are puffier
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-06-27 , DOI: 10.1051/0004-6361/202450587
Adrien Leleu , Jean-Baptiste Delisle , Remo Burn , André Izidoro , Stéphane Udry , Xavier Dumusque , Christophe Lovis , Sarah Millholland , Léna Parc , François Bouchy , Vincent Bourrier , Yann Alibert , João Faria , Christoph Mordasini , Damien Ségransan

A systematic, population-level discrepancy exists between the densities of exoplanets whose masses have been measured with transit timing variations (TTVs) versus those measured with radial velocities (RVs). Since the TTV planets are predominantly nearly resonant, it is still unclear whether the discrepancy is attributed to detection biases or to astrophysical differences between the nearly resonant and non resonant planet populations. We defined a controlled, unbiased sample of 36 sub-Neptunes characterised by Kepler, TESS, HARPS, and ESPRESSO. We found that their density depends mostly on the resonant state of the system, with a low probability (of ) that the mass of (nearly) resonant planets is drawn from the same underlying population as the bulk of sub-Neptunes. Increasing the sample to 133 sub-Neptunes reveals finer details: the densities of resonant planets are similar and lower than non-resonant planets, and both the mean and spread in density increase for planets that are away from resonance. This trend is also present in RV-characterised planets alone. In addition, TTVs and RVs have consistent density distributions for a given distance to resonance. We also show that systems closer to resonances tend to be more co-planar than their spread-out counterparts. These observational trends are also found in synthetic populations, where planets that survived in their original resonant configuration retain a lower density; whereas less compact systems have undergone post-disc giant collisions that increased the planet’s density, while expanding their orbits. Our findings reinforce the claim that resonant systems are archetypes of planetary systems at their birth.

中文翻译：

共振的亚海王星更加浮肿

使用凌日时间变化（TTV）测量质量的系外行星的密度与使用径向速度（RV）测量质量的系外行星的密度之间存在系统性的、群体水平的差异。由于 TTV 行星主要是近共振行星，目前尚不清楚这种差异是否归因于探测偏差或近共振行星群和非共振行星群之间的天体物理差异。我们定义了 36 个亚海王星的受控、无偏差样本，其特征为 Kepler、TESS、HARPS 和 ESPRESSO。我们发现它们的密度主要取决于系统的共振状态，（接近）共振行星的质量与大部分亚海王星来自相同的底层种群的概率很低。将样本增加到 133 个亚海王星，揭示了更精细的细节：共振行星的密度与非共振行星相似且较低，并且远离共振的行星的密度平均值和分布均增加。这种趋势也仅存在于具有 RV 特征的行星中。此外，TTV 和 RV 对于给定的共振距离具有一致的密度分布。我们还表明，接近共振的系统往往比分散的系统更共面。这些观测趋势也存在于合成族群中，其中以原始共振结构幸存下来的行星保留了较低的密度；而不太紧凑的系统经历了盘后巨大碰撞，增加了行星的密度，同时扩大了它们的轨道。我们的发现强化了这样的说法：共振系统是行星系统诞生时的原型。