AI 中文总结
本研究针对TRAPPIST-1f，通过纳入恒星污染的大气反演方法，发现短期JWST观测可获得其富CO₂大气的强证据，但需更多观测时间才能分离出CH₄等其他大气特征。
AI 中文摘要
TRAPPIST-1系统拥有7颗类地系外行星，轨道紧密，与主恒星的半径比值较大。若行星存在大气层，可通过透射光谱探测特定大气特征。在詹姆斯·韦布空间望远镜（JWST）发射前，对TRAPPIST-1行星大气可探测性的预测，均假设恒星表面处于原始状态。但JWST对TRAPPIST-1行星的初始观测显示，来自未被掩蔽的活动区的恒星污染产生的光谱特征，远强于任何行星大气的光谱特征。本文通过纳入恒星污染的大气反演方法，评估宜居带行星TRAPPIST-1f的大气可探测性：我们构建了富CO₂的宜居大气模型，生成对应的透射光谱，并纳入“最坏情况”的恒星污染光谱；随后在模拟的JWST观测数据上进行大气反演，观测数据涵盖中红外仪器（MIRI）低分辨率光谱仪（LRS，5-15微米）和近红外光谱仪（NIRSpec）棱镜模式（PRISM，0.6-5.3微米），假设恒星黑子光谱模型准确。研究发现：仅NIRSpec观测即可获得与MIRI+NIRSpec联合观测相似的结果；约10次凌星观测可获得CO₂的强证据（贝叶斯因子B>150），约50次凌星观测可获得CH₄的弱证据（B>3）；使用两种仪器的多达100次模拟凌星观测，均无法获得H₂O的证据。目前，在大气反演中准确处理极冷M型矮星的恒星污染仍存在诸多挑战，研究结果表明，尽管通过短期JWST观测可获得TRAPPIST-1f富CO₂大气的证据，但其他显著的大气特征需比以往研究指出的更多观测时间，才能从强恒星特征中分离出来。
英文摘要
The TRAPPIST-1 system offers seven terrestrial exoplanets with tight orbits and large radii ratios to the host star. If an atmosphere exists, transmission spectroscopy can be used to detect specific atmospheric features. Predictions of the atmospheric detectability of the TRAPPIST-1 planets prior to the launch of \textit{JWST} assumed pristine stellar surfaces. However, initial \textit{JWST} observations of the TRAPPIST-1 planets demonstrate that stellar contamination from unocculted active regions imparts significantly stronger spectral features than any planetary atmospheres. Here, we evaluate the atmospheric detectability of the habitable zone planet TRAPPIST-1f using atmospheric retrievals accounting for stellar contamination. We model a transmission spectrum given a CO$_2$-rich, habitable atmospheric model, and we include a "worst case" stellar contamination spectrum. We then perform atmospheric retrievals on simulated \textit{JWST} observations with MIRI LRS (5-15 \micron) and NIRSpec PRISM (0.6-5.3 \micron), assuming accurate starspot spectral models. We find that NIRSpec observations alone achieve similar results as MIRI and NIRSpec together. We find $\sim$10 transits obtains strong evidence ($B>150$) for CO$_2$, and $\sim$50 transits finds weak evidence ($B>3$) for CH$_4$. We could not retrieve evidence of H$_2$O with up to 100 simulated transits with both instruments. Many challenges remain to accurately account for stellar contamination for ultra-cool M-dwarfs in atmospheric retrievals, and our results show that, while evidence for a CO$_2$-rich atmosphere around TRAPPIST-1f can be found with a short \textit{JWST} program, other prominent atmospheric signatures can only be disentangled from strong stellar features with more observation time than previous studies have indicated.
Comments15 pages, 8 figures, in review by MNRAS
