AI 中文总结
该研究通过四次 JWST/NIRISS SOSS 凌星观测，发现 LHS 1140 b 无持续氦吸收，其大气逃逸信号可能由恒星 He I 变异性或视宁度相关仪器效应导致，需进一步观测验证。
AI 中文摘要
对温带类地行星大气的探测，有助于理解这些天体的形成、演化及潜在宜居性。温带行星 LHS 1140 b（平衡温度 $T_{\rm eq}=226$ K，半径跨越半径谷，$R_{\rm p}\boldsymbol{\times}1.7 R_\bigoplus$）的最新 WINERED 高分辨率光谱仪凌星观测，通过测量亚稳态氦三重线的过量吸收（$1.24\boldsymbol{\times}0.23$\u0025），探测到了行星大气逃逸现象，但后续第二次观测未检测到该信号。我们分析了四次 JWST/NIRISS SOSS 观测的 LHS 1140 b 凌星事件，以及两次 LHS 1140 c 的凌星事件，发现两颗行星均无氦吸收证据，所有振幅在 $1\boldsymbol{\times}\boldsymbol{\times}$ 范围内均与零一致。对于 LHS 1140 b，我们得出的 $3\boldsymbol{\times}$ 上限为 $0.72$–$1.21$\u0025。单次观测在 $2.6$–$3.7\boldsymbol{\times}$ 范围内不支持此前 WINERED 探测到的吸收信号，而联合约束则在 $4.5\boldsymbol{\times}$ 范围内不支持存在持续信号。我们发现 LHS 1140 的恒星 He I 线在 NIRPS 和 WINERED 观测历元间存在显著变化，其强度和分数变异性均与其他 M 型矮星的行为一致。我们还发现 2024 年 He I 深度与视宁度之间存在中等相关性，表明可能存在与视宁度相关的仪器贡献。如果该高分辨率探测确实来自行星，则此类大气逃逸事件的发生率必须相对较低（$f=22_{-12}^{+17}$\u0025）；或者，恒星 He I 变异性可能是导致报告的过量吸收的原因。需要额外的凌星内和凌星外高分辨率观测来区分这些情景。
英文摘要
The search for atmospheres on temperate terrestrial planets is important for understanding how these objects form and evolve, and their potential habitability. Recent transit observations of LHS 1140 b, a temperate ($T_{\rm eq}=226$ K) planet straddling the radius valley ($R_{\rm p}\approx1.7 R_\oplus$), with the WINERED high-resolution spectrograph yielded a detection of planetary atmospheric escape through the measurement of excess absorption ($1.24\pm0.23\%$) in the metastable helium triplet, although a later second visit resulted in a non-detection. We analyze four transits of LHS 1140 b and two of LHS 1140 c observed with JWST/NIRISS SOSS. We find no evidence of helium absorption in either planet, with all amplitudes consistent with zero within $1σ$. For LHS 1140 b, we derive $3σ$ upper limits of $0.72$--$1.21\%$. Individual visits disfavor the reported WINERED absorption at $2.6$--$3.7σ$, while their joint constraint disfavors a persistent signal at $4.5σ$. We find that the stellar He I line of LHS 1140 varies substantially between NIRPS and WINERED epochs, with both its strength and fractional variability consistent with the behavior of other M dwarfs. We also identify a moderate correlation between the 2024 He I depth and seeing, suggesting a possible seeing-dependent instrumental contribution. If the high-resolution detection is indeed planetary, the rate of such atmospheric loss events must be relatively low ($f=22_{-12}^{+17}\%$). Alternatively, stellar He I variability may contribute to the reported excess absorption. Additional high-resolution observations, both in and out of transit, are required to distinguish between these scenarios.
CommentsSubmitted to ApJL
