The origin of Hot Jupiters (HJs) is disputed between a variety of in situ and ex situ formation scenarios. One of the early proposed ex situ scenarios was the Eccentric Kozai–Lidov (EKL) mechanism combined with tidal circularization, which can produce HJs with the aid of a stellar or planetary companion. However, observations have revealed a lack of stellar companions to HJs, which challenges the importance of the binary star-driven-EKL-plus-tides scenario. In this work, we explore so far unaccounted-for stellar evolution effects on HJ formation, in particular the effect of white dwarf (WD) formation. Gaia observations have revealed that WDs often undergo a kick during formation, which can alter a binary’s orbital configuration or even unbind it. Based on this WD kick, in this Letter, we propose and explore two novel HJ formation pathways: (1) HJs that are presently orbiting single stars but were initially formed in a binary that was later unbound by a WD kick; (2) binaries that survive the WD kick can trigger enhanced EKL oscillations and lead to second-generation HJ formation. We demonstrate that the majority of seemingly single HJs could have formed in binary star systems. As such, HJ formation in binaries via the EKL mechanism could be one of the dominant HJ formation pathways, and our results highlight that unaccounted-for stellar evolution effects, like WD formation, can obscure the actual origin of observed exoplanet populations.

中文翻译：

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两种新颖的热木星形成途径：白矮星踢如何塑造热木星种群


热木星 （HJ） 的起源在各种原位和非原位形成情景之间存在争议。早期提出的非原位情景之一是偏心 Kozai-Lidov （EKL） 机制与潮汐循环相结合，它可以在恒星或行星伴星的帮助下产生 HJ。然而，观测表明 HJ 缺乏恒星伴星，这挑战了双星驱动的 EKL 加潮汐情景的重要性。在这项工作中，我们探讨了迄今为止尚未解释的恒星演化对 HJ 形成的影响，特别是白矮星 （WD） 形成的影响。Gaia 的观测表明，WD 在形成过程中经常会受到踢击，这可以改变双星的轨道配置，甚至解除束缚。基于这个 WD kick，在这封信中，我们提出并探索了两种新颖的 HJ 形成途径：（1） HJ 目前围绕单颗恒星运行，但最初是在双星中形成的，后来被 WD kick 解开;（2） 在 WD kick 中幸存下来的二进制文件可以触发增强的 EKL 振荡并导致第二代 HJ 的形成。我们证明了大多数看似单一的 HJ 可能是在双星系统中形成的。因此，通过 EKL 机制在双星中形成 HJ 可能是主要的 HJ 形成途径之一，我们的结果强调，未解释的恒星演化效应，如 WD 形成，可以掩盖观察到的系外行星种群的实际起源。