TOI-4468 行星系（planetary system）的发现与表征：一颗带有孤立邻近带外行星（outer planet）的凌（transit）热木星（hot Jupiter）

本文报告了围绕恒星（star）TOI-4468 运行的两颗行星的发现，包括一颗热木星和一颗邻近的带外亚海王星（sub-Neptune）。该系统在目前的系外行星（exoplanet）普查中独树一帜，其热木星附近存在一颗带外伴星，且没有内侧伴星。通过联合拟合径向速度（radial velocity）测量数据与凌星系外行星巡天卫星（TESS）及多个地基天文台（ground-based observatory）的测光（photometry）数据，研究人员确定了这两颗行星的轨道周期（orbital period）、质量和半径。

arXiv:2608.25208v1 Announce Type: new Abstract: We report the discovery of two planets, a hot Jupiter and a nearby outer sub-Neptune, orbiting the star TOI-4468. This system is unique among the current exoplanet census in that it features a close outer companion to a hot Jupiter without an accompanying inner companion. By jointly fitting radial velocity measurements taken with the NEID spectrograph and transit photometry from TESS and several ground-based observatories, we constrain the orbital periods, masses, and radii of these two planets. We confirm the planetary nature of the hot Jupiter TOI-4468 b ($R = 1.01 R_J$, $m = 0.54 M_J$, $P = 2.77$ days). We also validate the outer planet TOI-4468 c ($R = 0.28 R_J$, $P = 7.01$ days) statistically, incorporating constraints from ground-based observations. We also identify, but cannot confirm, an additional radial velocity signal which may be due to an outer giant in this system with an orbital period of 624 days. From the observed geometry of this system, we argue that it must never have encountered an early secular resonance that is thought to excite the mutual inclination of other hot Jupiter/outer companion systems. We discuss the possibility of an undetected inner companion, as well