利用JWST NIRISS SOSS对TRAPPIST-1 f进行大气侦察：无凌星光源效应的证据
Atmospheric Reconnaissance of TRAPPIST-1 f with JWST NIRISS SOSS: No Evidence for the Transit Light Source Effect
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中文总结 AI 辅助
本研究利用JWST NIRISS SOSS获取TRAPPIST-1 f的凌星光谱，未发现未被掩蔽恒星表面不均匀性的污染证据，排除了其表面压力高于约20毫巴的氢/氦主导大气。
中文摘要 AI 辅助
在仅三年多的运行时间里，詹姆斯·韦布空间望远镜（JWST）已观测到TRAPPIST-1系统的全部七颗行星。研究发现，除存在高空气溶胶的情况外，两颗最内侧行星几乎没有大气。本文报告了对宜居带系外行星TRAPPIST-1 f的首次JWST凌星光谱观测结果，这些观测通过近红外成像仪和无缝摄谱仪（NIRISS）的单目标 slitless 光谱仪（SOSS）在五次凌星过程中完成。每次观测时段至少发生一次恒星耀斑，但与更内侧的TRAPPIST-1行星观测不同，未发现未被掩蔽的恒星表面不均匀性对凌星光谱造成污染的证据。该未检测结果并不保证该行星未来所有凌星观测中都不存在未被掩蔽的不均匀性，其原因可能是TRAPPIST-1 f的凌星弦在观测时具有与凌星外的平均可见恒星半球相似的特性。凌星光谱显示出从-365 ppm/μm到15 ppm/μm的斜率，我们将其归因于恒星变异性，即耀斑和/或更小尺度的事件。受耀斑影响最小的观测结果以95%的置信度排除了表面压力高于约20毫巴的以氢/氦为主的大气。对于平均分子质量较高的大气，表面压力的精确上限取决于数据 reduction pipeline（处理流程）以及对凌星光谱中残余斜率的处理方式。
英文摘要
In just over three years of operation, JWST has observed all seven planets of the TRAPPIST-1 system. The two innermost planets were found to have little to no atmosphere, barring the presence of high-altitude aerosols. Here we present the first JWST transit spectra of the habitable-zone exoplanet TRAPPIST-1 f, which were obtained with NIRISS SOSS over the course of five transits. At least one stellar flare occurred in each visit, but unlike observations of closer-in TRAPPIST-1 planets, no evidence for contamination of the transit spectra from unocculted stellar surface heterogeneities was found. This non-detection does not guarantee the absence of unocculted heterogeneities in all future transit observations of this planet, and it could be explained by the transit chord of TRAPPIST-1 f having properties similar to the average, out-of-transit, visible stellar hemisphere at the time of observation. The transit spectra exhibit slopes ranging from -365 ppm/um down to 15 ppm/um, which we attribute to stellar variability, that is, flares and/or smaller-scale events. The visits least affected by flares rule out H2/He-dominated atmospheres with surface pressures higher than about 20 mbar at 95% confidence. For high-mean-molecular-mass atmospheres, the exact upper limits on surface pressures depend on the reduction pipeline and on the treatment of the residual slopes in the transit spectra.
发表机构
- Institut Trottier de recherche sur les exoplanètes, Département de Physique, Université de Montréal（蒙特利尔大学特罗蒂尔系外行星研究所物理系）
- Department of Astronomy, University of Michigan（密歇根大学天文学系）
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