CHEMICAL TIMESCALES IN THE ATMOSPHERES OF HIGHLY ECCENTRIC EXOPLANETS
- Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States)
Close-in exoplanets with highly eccentric orbits are subject to large variations in incoming stellar flux between periapse and apoapse. These variations may lead to large swings in atmospheric temperature, which in turn may cause changes in the chemistry of the atmosphere from higher CO abundances at periapse to higher CH{sub 4} abundances at apoapse. Here, we examine chemical timescales for CO{r_reversible}CH{sub 4} interconversion compared to orbital timescales and vertical mixing timescales for the highly eccentric exoplanets HAT-P-2b and CoRoT-10b. As exoplanet atmospheres cool, the chemical timescales for CO{r_reversible}CH{sub 4} tend to exceed orbital and/or vertical mixing timescales, leading to quenching. The relative roles of orbit-induced thermal quenching and vertical quenching depend upon mixing timescales relative to orbital timescales. For both HAT-P-2b and CoRoT-10b, vertical quenching will determine disequilibrium CO{r_reversible}CH{sub 4} chemistry at faster vertical mixing rates (K{sub zz} > 10{sup 7} cm{sup 2} s{sup -1}), whereas orbit-induced thermal quenching may play a significant role at slower mixing rates (K{sub zz} < 10{sup 7} cm{sup 2} s{sup -1}). The general abundance and chemical timescale results-calculated as a function of pressure, temperature, and metallicity-can be applied for different atmospheric profiles in order to estimate the quench level and disequilibrium abundances of CO and CH{sub 4} on hydrogen-dominated exoplanets. Observations of CO and CH{sub 4} on highly eccentric exoplanets may yield important clues to the chemical and dynamical properties of their atmospheres.
- OSTI ID:
- 22092318
- Journal Information:
- Astrophysical Journal, Vol. 757, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
Similar Records
QUENCHING OF CARBON MONOXIDE AND METHANE IN THE ATMOSPHERES OF COOL BROWN DWARFS AND HOT JUPITERS
Mass-Radius Relationships for Exoplanets