%0 Generic %1 malik2019analyzing %A Malik, Matej %A Kempton, Eliza M. R. %A Koll, Daniel D. B. %A Mansfield, Megan %A Bean, Jacob L. %A Kite, Edwin %D 2019 %K atmosphere exoplanet mdwarf %T Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets %U http://arxiv.org/abs/1907.13135 %X The highly anticipated launch of JWST will open up the possibility of comprehensively measuring the emission spectra of rocky exoplanets orbiting M dwarfs to detect and characterize their atmospheres. In preparation for this opportunity, we present model atmospheres for three M-dwarf planets particularly amenable to secondary eclipse spectroscopy -- TRAPPIST-1b, GJ 1132b, and LHS 3844b. Using three limiting cases of candidate atmospheric compositions (pure H2O, pure CO2 and solar abundances) we calculate temperature-pressure profiles and emission and reflection spectra in radiative-convective equilibrium, including the effects of a solid surface at the base of the atmosphere. Our results differ appreciably from simpler parameterized models of super-Earth atmospheres in terms of the overall temperatures and the temperature gradient, which has important observational consequences. We find that the atmospheric radiative transfer is significantly influenced by the cool M-star irradiation; H2O and CO2 absorption bands in the near-infrared are strong enough to absorb a sizeable fraction of the incoming stellar light at low pressures, which leads to temperature inversions in the upper atmosphere. The non-gray band structure of gaseous opacities in the infrared is hereby an important factor. Opacity windows are muted at higher atmospheric temperatures, so we expect temperature inversions to be common only for sufficiently cool planets. We also find that pure CO2 atmospheres exhibit lower overall temperatures and stronger reflection spectra compared to models of the other two compositions. We estimate that for GJ 1132b and LHS 3844b we should be able to distinguish between different atmospheric compositions with JWST. The emission lines from the predicted temperature inversions are currently hard to measure, but high resolution spectroscopy with future ELTs may be able to detect them.

@misc{malik2019analyzing, abstract = {The highly anticipated launch of JWST will open up the possibility of comprehensively measuring the emission spectra of rocky exoplanets orbiting M dwarfs to detect and characterize their atmospheres. In preparation for this opportunity, we present model atmospheres for three M-dwarf planets particularly amenable to secondary eclipse spectroscopy -- TRAPPIST-1b, GJ 1132b, and LHS 3844b. Using three limiting cases of candidate atmospheric compositions (pure H2O, pure CO2 and solar abundances) we calculate temperature-pressure profiles and emission and reflection spectra in radiative-convective equilibrium, including the effects of a solid surface at the base of the atmosphere. Our results differ appreciably from simpler parameterized models of super-Earth atmospheres in terms of the overall temperatures and the temperature gradient, which has important observational consequences. We find that the atmospheric radiative transfer is significantly influenced by the cool M-star irradiation; H2O and CO2 absorption bands in the near-infrared are strong enough to absorb a sizeable fraction of the incoming stellar light at low pressures, which leads to temperature inversions in the upper atmosphere. The non-gray band structure of gaseous opacities in the infrared is hereby an important factor. Opacity windows are muted at higher atmospheric temperatures, so we expect temperature inversions to be common only for sufficiently cool planets. We also find that pure CO2 atmospheres exhibit lower overall temperatures and stronger reflection spectra compared to models of the other two compositions. We estimate that for GJ 1132b and LHS 3844b we should be able to distinguish between different atmospheric compositions with JWST. The emission lines from the predicted temperature inversions are currently hard to measure, but high resolution spectroscopy with future ELTs may be able to detect them.}, added-at = {2019-08-01T17:19:02.000+0200}, author = {Malik, Matej and Kempton, Eliza M. R. and Koll, Daniel D. B. and Mansfield, Megan and Bean, Jacob L. and Kite, Edwin}, biburl = {https://www.bibsonomy.org/bibtex/24351b3d5619b0027c3402321229ee9bb/superjenwinters}, description = {Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets}, interhash = {a497eb3718776c1e9335a2eb4c989eba}, intrahash = {4351b3d5619b0027c3402321229ee9bb}, keywords = {atmosphere exoplanet mdwarf}, note = {cite arxiv:1907.13135Comment: Submitted to ApJ. Also see these three companion papers: 1. Mansfield et al (submitted), "Identifying Atmospheres on Rocky Exoplanets Through Inferred High Albedo", 2. Koll et al (submitted), "Identifying candidate atmospheres on rocky M dwarf planets via eclipse photometry", 3. Koll (submitted) "A Scaling Theory for Atmospheric Heat Redistribution on Rocky Exoplanets"}, timestamp = {2019-08-01T17:19:02.000+0200}, title = {Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets}, url = {http://arxiv.org/abs/1907.13135}, year = 2019 }