2017/11/29 by Kyle Sheppard, Kyle B. Sheppard, Avi M. Mandell +6 · 3 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomy and Astrophysical Research #Atmosphere of Jupiter #Atmospheric escape #Eclipse #Hot Jupiter #Metallicity #Planet #Planetary science #Stellar, planetary, and galactic studies #Thermal #Thermal emission #astro-ph.EP
paper · pdf · doi:10.3847/2041-8213/aa9ae9
7 pages, 4 figures, 1 table, published in ApJ Letters 11/29
openalex publication_date 2017/11/29 · arxiv created 2017/12/01 · arxiv updated 2017/12/04 · openalex created_date 2017/12/04 · openalex updated_date 2026/08/05
Abstract We find evidence for a strong thermal inversion in the dayside atmosphere of the highly irradiated hot Jupiter WASP-18b ( , ) based on emission spectroscopy from Hubble Space Telescope secondary eclipse observations and Spitzer eclipse photometry. We demonstrate a lack of water vapor in either absorption or emission at 1.4 μ m. However, we infer emission at 4.5 μ m and absorption at 1.6 μ m that we attribute to CO, as well as a non-detection of all other relevant species (e.g., TiO, VO). The most probable atmospheric retrieval solution indicates a C/O ratio of 1 and a high metallicity ( solar). The derived composition and T/P profile suggest that WASP-18b is the first example of both a planet with a non-oxide driven thermal inversion and a planet with an atmospheric metallicity inconsistent with that predicted for Jupiter-mass planets at . Future observations are necessary to confirm the unusual planetary properties implied by these results.