Hubble WFC3 Spectroscopy of the Rocky Planet L 98-59 b: No evidence of a cloud-free primordial atmosphere


Spectral light curves for the transmission spectra. Left panel: trend-corrected spectral light curves with best-fit model applied. The right panel shows the residuals. For each spectrum we present the values ​​of σ, chi-square (χ 2 ), and AC. astro-ph.EP

We use archived data from the transiting exoplanet L~98-59~b’s HST to establish constraints on its potentially hot atmosphere.

We analyze the data from five transit visits and extract the final combined transmission spectrum using Iraclis.

Then we use the inverse atmospheric retrieval code TauREx to analyze the combined transmission spectrum. There is a faint absorption feature near 1.40 μm and 1.55 μm in the transmission spectrum that can be modeled by a cloudy atmosphere with abundant HCN.

However, the unrealistically high abundance of derived HCN cannot be explained by any chemical equilibrium model with reasonable assumptions. Therefore, the most likely scenario is that L~98-59~b has a flat, structureless transmission spectrum in the WFC3/G141 bandpass due to a thin atmosphere with high average molecular weight, an atmosphere with an opaque aerosol layer, or no atmosphere. and L~98-59~b is very unlikely to have a clear hydrogen-dominated primary atmosphere.

Due to the narrow wavelength coverage and low spectral resolution of the HST/WFC3 G141 Grima observation, we cannot distinguish these different scenarios from each other. Our simulation shows that future measurements with higher precision over longer wavelengths from the James Webb Space Telescope (JWST) can be used to better characterize the planetary atmosphere of L~98-59~b.

Li Zhou, Bo Ma, Yonghao Wang, and Yinan Zhu

Comment: 15 pages, 11 figures, 6 tables, accepted for publication in AJ
Subjects: Astrophysics of the Earth and Planets (astro-ph.EP)
Cite as: arXiv:2210.10699 [astro-ph.EP] (or arXiv:2210.10699v1 [astro-ph.EP] for this version)
Submission History
By: Li Zhou

[v1] Wednesday 19 Oct 2022 16:26:14 UTC (1154 KB)


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