High-resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
High-resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b
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DOI：
10.3847/1538-3881/acbd39
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发表时间：
2022-12
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通讯作者：
A. Ridden-Harper;S. K. Nugroho;L. Flagg;R. Jayawardhana;J. Turner;E. D. de Mooij;R. MacDonald;E. Deibert;Motohide Tamura;T. Kotani;T. Hirano;M. Kuzuhara;M. Omiya;N. Kusakabe
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作者：
A. Ridden-Harper;S. K. Nugroho;L. Flagg;R. Jayawardhana;J. Turner;E. D. de Mooij;R. MacDonald;E. Deibert;Motohide Tamura;T. Kotani;T. Hirano;M. Kuzuhara;M. Omiya;N. Kusakabe
绕M矮星运行的类地系外行星是利用现有或不久的将来的仪器进行透射光谱学的有希望的目标。这些岩石行星的大气成分仍然是一个悬而未决的问题，特别是考虑到来自其宿主M矮星的高X射线和紫外线通量可以驱动大气逃逸。1.3 R的太阳系外行星GJ 486 b（T eq = 700 K）围绕着一颗M3.5星星运行，预计在已知的类地系外行星中具有最强的透射光谱信号。我们使用三台不同的高分辨率光谱仪观测了GJ 486 b的三次凌日：斯巴鲁望远镜上的IRD，双子座南望远镜上的IGRINS和加拿大-法国-夏威夷望远镜上的SPIRou。我们通过互相关方法从各种各样的分子物种中搜索大气吸收，但没有检测到任何稳健的大气信号。尽管如此，我们的观测是足够敏感的，以排除几个明确的大气场景通过注入和恢复测试，并扩展到陆地制度的比较系外行星学。我们的研究结果表明，GJ 486 b没有一个明确的H2/He占主导地位的大气，也没有一个明确的100%的水蒸气大气。其他具有高平均分子量或H2/He主导的大气层的次级大气层仍然是可能的。我们的发现提供了进一步的证据，表明绕M矮星运行的类地行星可能会经历显著的大气损失。
Terrestrial exoplanets orbiting M-dwarf stars are promising targets for transmission spectroscopy with existing or near-future instrumentation. The atmospheric composition of such rocky planets remains an open question, especially given the high X-ray and ultraviolet flux from their host M dwarfs that can drive atmospheric escape. The 1.3 R ⊕ exoplanet GJ 486b (T eq ∼ 700 K), orbiting an M3.5 star, is expected to have one of the strongest transmission spectroscopy signals among known terrestrial exoplanets. We observed three transits of GJ 486b using three different high-resolution spectrographs: IRD on Subaru, IGRINS on Gemini-South, and SPIRou on the Canada–France–Hawai’i Telescope. We searched for atmospheric absorption from a wide variety of molecular species via the cross-correlation method, but did not detect any robust atmospheric signals. Nevertheless, our observations are sufficiently sensitive to rule out several clear atmospheric scenarios via injection and recovery tests, and extend comparative exoplanetology into the terrestrial regime. Our results suggest that GJ 486b does not possess a clear H2/He-dominated atmosphere, nor a clear 100% water-vapor atmosphere. Other secondary atmospheres with high mean molecular weights or H2/He-dominated atmospheres with clouds remain possible. Our findings provide further evidence suggesting that terrestrial planets orbiting M-dwarf stars may experience significant atmospheric loss.