标题： 恒星HIP 41378可能与其长周期行星群体不对齐 显示英文标题

标题： The star HIP 41378 potentially misaligned with its cohort of long-period planets

摘要： 恒星自转轴与行星轨道之间的偏角，通过罗斯特-麦克劳克林（RM）效应检测到，是行星系统形成历史的指示器。 尽管偏角测量已被广泛应用于热木星和短周期行星，但由于观测挑战，尤其是它们的长凌日持续时间，冷且长周期行星的测量仍然很少。 我们报告了对HIP 41378 f的19小时长凌日的RM效应检测，这是一颗轨道周期为542天的温带巨行星，通过全球光谱活动观测到。 基于恒星自转周期的测量，我们测得一个轻微的投影偏角为21 $\pm$ 8度和一个显著的三维自转-轨道角度为52 $\pm$ 6度。 HIP 41378 f是一个包含5颗凌日行星的系统的一部分，这些行星接近平均运动共振。 观测到的不对齐可能反映了恒星自转轴相对于原行星盘的原始倾斜，而不是动力学相互作用。 HIP 41378 f是第一个通过RM效应观测到的非偏心长周期（P>100天）行星，为行星形成理论提供了新的约束。 这一观测应促进通过国际合作在更长的轨道距离范围内探索行星偏角。 显示英文摘要

摘要： The obliquity between the stellar spin axis and the planetary orbit, detected via the Rossiter-McLaughlin (RM) effect, is a tracer of the formation history of planetary systems. While obliquity measurements have been extensively applied to hot Jupiters and short-period planets, they remain rare for cold and long-period planets due to observational challenges, particularly their long transit durations. We report the detection of the RM effect for the 19-hour-long transit of HIP 41378 f, a temperate giant planet on a 542-day orbit, observed through a worldwide spectroscopic campaign. We measure a slight projected obliquity of 21 $\pm$ 8 degrees and a significant 3D spin-orbit angle of 52 $\pm$ 6 degrees, based on the measurement of the stellar rotation period. HIP 41378 f is part of a 5-transiting planetary system with planets close to mean motion resonances. The observed misalignment likely reflects a primordial tilt of the stellar spin axis relative to the protoplanetary disk, rather than dynamical interactions. HIP 41378 f is the first non-eccentric long-period (P>100 days) planet observed with the RM effect, opening new constraints on planetary formation theories. This observation should motivate the exploration of planetary obliquities across a longer range of orbital distances through international collaboration.