2021/07/31 by Morgan MacLeod, Antonija Oklopčić · 54 citations
Physics and Astronomy · #Astrobiology #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Exoplanet #Physics #Planet #Stellar, planetary, and galactic studies #astro-ph.EP #astro-ph.SR
paper · pdf · open access · doi:10.3847/1538-4357/ac46ce
published in The Astrophysical Journal 926(2), 226 (IOP Publishing) · Accepted for publication in AAS Journals. Associated data and software at: https://zenodo.org/record/5750747 and https://zenodo.org/record/5750777
openalex created_date 2021/08/02 · openalex publication_date 2022/02/01 · arxiv created 2022/02/02 · arxiv updated 2022/03/09 · openalex updated_date 2026/08/06
Atmospheric escape from close-in exoplanets is thought to be crucial in shaping observed planetary populations. Recently, significant progress has been made in observing this process in action through excess absorption in transit spectra and narrowband light curves. We model the escape of initially-homogeneous planetary winds interacting with a stellar wind. The ram pressure balance of the two winds governs this interaction. When the impingement of the stellar wind on the planetary outflow is mild or moderate, the planetary outflow expands nearly spherically through its sonic surface before forming a shocked boundary layer. When the confinement is strong, the planetary outflow is redirected into a cometary tail before it expands to its sonic radius. The resultant transmission spectra at the He 1083 nm line are accurately represented by a 1D spherical wind solution in cases of mild to moderate stellar wind interaction. In cases of strong stellar wind interaction, the degree of absorption is enhanced and the cometary tail leads to an extended egress from transit. The crucial features of the wind--wind interaction are, therefore, encapsulated in the light curve of He 1083 nm equivalent width as a function of time. The possibility of extended He 1083 nm absorption well beyond the optical transit carries important implications for planning "out-of-transit" observations that serve as a baseline for in-transit data.