发表机构
Princeton University; Universidad Adolfo Ibáñez; California Institute of Technology; University of Amsterdam; ASTRON, Netherlands Institute for Radio Astronomy（普林斯顿大学; 阿道夫·伊瓦涅斯大学; 加州理工学院; 阿姆斯特丹大学; 荷兰射电天文研究所（ASTRON））
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过Keck Planet Finder等设备测得热恒星WASP-195的热海王星倾角，发现其轨道自旋对齐，结合数据排除近3天文单位内木星质量行星，解释了热恒星周围海王星倾角测量稀少的原因并提出相关探测思路。
AI 中文摘要
恒星倾角为行星系统的形成和迁移历史提供了重要线索，但对于海王星质量行星，尤其是那些环绕热恒星（Kraft break以上）的行星，这类测量仍然十分稀少。在此，我们呈现利用Keck Planet Finder和NEID摄谱仪获得的热恒星/热海王星系统WASP-195（有效温度T_eff=6470±100 K，恒星自转速度v sin i_⋆=10.5±1.1 km s⁻¹）的Rossiter-McLaughlin效应观测结果。对这些观测数据、存档测光数据及存档径向速度数据的联合分析得出，天空投影恒星倾角λ=-10±7°，与自旋轨道对齐一致。这使WASP-195成为少数拥有已测倾角的热恒星/热海王星系统之一。来自SOPHIE的存档径向速度数据以5σ置信度排除了约3天文单位范围内存在木星质量行星的可能。该对齐且近圆的轨道自然与盘驱动迁移的历史相符，尽管共面高离心率迁移或洛希瓣溢流也无法被排除。我们还研究了为何围绕热恒星的海王星已测倾角如此之少。这种稀缺性可能反映了两个因素的结合：热恒星周围短周期海王星的内在发生率较低，以及在该区域确认行星候选体存在困难——此处快速的恒星自转加宽了谱线，阻碍了常规径向速度确认。快速自转也提高了Rossiter-McLaughlin效应的可探测性，这一特征可帮助拓宽行星确认的瓶颈，同时扩大围绕热恒星的小型行星的倾角普查范围。
英文摘要
Stellar obliquities provide important clues as to the formation and migration histories of planetary systems, but measurements remain scarce for Neptune-mass planets, especially those orbiting hot stars (above the Kraft break). Here we present observations of the Rossiter-McLaughlin effect in the hot-star/hot-Neptune system WASP-195 ($T_{\rm eff}=6470\pm100$ K, $v\sin{i_\star}=10.5\pm1.1$ km s$^{-1}$) obtained with the Keck Planet Finder and NEID spectrographs. A joint analysis of these observations, archival photometry, and archival radial velocities yields a sky-projected stellar obliquity of $λ=-10\pm7^\circ$, consistent with spin-orbit alignment. This makes WASP-195 one of the few hot-star/hot-Neptune systems with a measured obliquity. Archival radial velocities from SOPHIE exclude Jupiter-mass planets within approximately 3 au at $5σ$ confidence. The aligned and nearly circular orbit is naturally consistent with a history of disk-driven migration, although coplanar high-eccentricity migration or Roche-lobe overflow cannot be ruled out. We also investigate why so few Neptunes around hot stars have measured obliquities. Their scarcity likely reflects a combination of the lower intrinsic occurrence of short-period Neptunes around hot stars and the difficulty of confirming planet candidates in this regime, where rapid stellar rotation broadens spectral lines and hampers conventional radial-velocity confirmation. Rapid rotation also increases the detectability of the Rossiter-McLaughlin effect, a feature that could help to widen the planet confirmation bottleneck while expanding the obliquity census of small planets around hot stars.
Comments16 pages, 4 figures. Accepted for publication in AJ
