2023/06/23 by Billy Edwards, Quentin Changeat, Edwards, Billy +57
Physics and Astronomy · #Astro and Planetary Science #Astronomy and Astrophysical Research #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2306.13645
openalex publication_date 2023/06/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot Neptune desert, that has been observed with HST WFC3 G102 and G141. The combined transmission spectrum, which covers 0.8 - 1.6 μm, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H\rm 2O, CO\rm 2 and FeH with a significance of 3.1 σ, 2.4 σ and 2.1 σ, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 μm Helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which is not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyman α.