基于四次JWST NIRISS凌星观测对LHS 1140 b氦吸收的严格限制
Strict Limits on Helium Absorption from LHS 1140 b from Four JWST NIRISS Transits
- Department of Astronomy & Astrophysics, University of Chicago（芝加哥大学天文与天体物理系）
- NSERC（加拿大自然科学与工程研究理事会）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过四次JWST NIRISS凌星观测，对LHS 1140 b的氦吸收给出严格限制，排除了与Cherubim等人观测结果相当的氦吸收，为该行星大气演化研究提供关键约束。
AI中文摘要：
LHS 1140 b是一颗轨道位于宿主恒星宜居带的行星，半径为1.7 $R_\bigoplus$，质量为5.6 $M_\bigoplus$，是备受关注的研究目标。近期Cherubim等人（2026年）发表了对LHS 1140 b大气中逃逸的亚稳态氦的探测结果，这是该行星大气存在的首个明确推断，同时表明其大气富含氦、贫氢，这是数十亿年分馏质量损失的预期结果。本研究分析了2023年12月至2026年7月期间，JWST的NIRISS仪器获取的LHS 1140 b的四次存档凌星观测，以寻找氦吸收的证据。与平连续谱相比，四次观测均不支持氦吸收的存在，几率比介于3.9至11.6:1之间。与Cherubim等人（2026年）观测到的幅度和宽度相当的氦吸收，被数据强烈排除，与平连续谱相比的几率比介于300至8.6×10⁴:1之间——不过需注意的是，所有JWST凌星观测均未与Cherubim等人（2026年）的探测结果处于同一时间。本研究还对这四次观测的凌星外恒星光谱，以及另一颗行星c的额外JWST NIRISS凌星观测进行了拟合，以寻找恒星变异性的证据，发现所有五组数据集均得到一致的光球和不均匀性参数。总体而言，本研究为LHS 1140 b的氦逃逸提供了一组严格限制，将对未来研究这颗引人入胜的行星的性质和演化具有重要价值。
英文摘要：
Orbiting in the habitable zone of its host star, the 1.7 $R_\oplus$, 5.6 $M_\oplus$ planet LHS 1140 b is a target of great interest. Recently Cherubim et al. (2026) published a detection of metastable He escaping from the atmosphere of LHS 1140 b, simultaneously providing the first concrete inference of an atmosphere on this planet and indicating that the atmosphere is He-rich and H-poor as would be expected due to Gyrs of fractionated mass loss. In this work, we analyze four archival transits of LHS 1140 b, spanning Dec 2023 to Jul 2026, taken with the NIRISS instrument on JWST, for evidence of He absorption. Each of the four visits disfavours the presence of He absorption compared to a flat continuum with odds ratios ranging from 3.9--11.6:1. He absorption with an amplitude and width equivalent to that observed by Cherubim et al. (2026) is strongly ruled out by the data with odds ratios from 300--8.6$\times$10$^4$:1 compared to a flat continuum --- though it should be noted that none of the JWST transits are contemporaneous with the Cherubim et al. (2026) detection. We also fit the absolute out-of-transit stellar spectra from these four visits, as well as an additional JWST NIRISS transit of planet c, to search for evidence of stellar variability, but find consistent photosphere and herterogeneity parameters in all five datasets. In all, our work provides a set of strict limits on He escape from LHS 1140 b that will be valuable to future studies into the nature and evolution of this intriguing world.
