Hubble WFC3 Spectroscopy of the Terrestrial Planets L~98-59~c \& d: No Evidence for a Clear Hydrogen Dominated Primary Atmosphere

The nearby bright M-dwarf star L~98-59 has three terrestrial-sized planets. One challenge remaining in characterizing atmospheres around such planets is that it is not known a priori whether they possess any atmospheres.

Here we report the study of the atmospheres of L~98-59~c and L~98-59~d using the near-infrared spectral data from the G141 grism of HST/WFC3. We can reject the hypothesis of a clear atmosphere dominated by hydrogen and helium at a confidence level of ∼ 3~sigma for both planets.

Thus they may have a primary hydrogen-dominated atmosphere with an opaque cloud layer, or have lost their primary hydrogen-dominated atmosphere and re-established a secondary thin atmosphere, or have no atmosphere at all. We cannot distinguish between these scenarios for the two planets using the current HST data. Future observations with JWST would be capable of confirming the existence of atmospheres around L~98-59~c and d and determining their compositions.

Li Zhou, Bo Ma, Yonghao Wang, Yinan Zhu

Comments: 24pages, 18 figures, 5 tables, accepted to RAA
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2212.09526 [astro-ph.EP] (or arXiv:2212.09526v1 [astro-ph.EP] for this version)
Submission history
From: Li Zhou
[v1] Mon, 19 Dec 2022 15:14:53 UTC (16,027 KB)
https://arxiv.org/abs/2212.09526
Astrobiology, Astrochemistry