Statistics – Computation
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21532705m&link_type=abstract
American Astronomical Society, AAS Meeting #215, #327.05; Bulletin of the American Astronomical Society, Vol. 42, p.424
Statistics
Computation
Scientific paper
We present a new method to constrain exoplanet atmosphere properties based on photometric and spectroscopic data. Our new method gives error contours in chemical compositions, average vertical temperature structure, and day-night redistribution in the planet atmosphere. Our method involves large-scale computation of millions of 1D atmosphere models, spanning the large parameter space allowed by current data. To meet this end, we have developed a parametric pressure-temperature (P-T) profile coupled with line-by-line radiative transfer, hydrostatic equilibrium, and energy balance, along with prescriptions for non-equilibrium molecular compositions and energy redistribution. The major difference from traditional 1D radiative transfer models is the parametric P-T profile, which essentially means adopting radiative flux balance only at the top of the atmosphere and not in each layer. The parametric P-T profile captures the basic physical features of temperature structures in planetary atmospheres (including temperature inversions), and fits a wide range of published P-T profiles, including those of solar system planets. We apply our temperature and abundance retrieval method to Spitzer and HST observations of two exoplanets with the best data, HD 189733b and HD 209458b. For HD 189733b, we find efficient day-night redistribution of energy in the atmosphere, and molecular abundance constraints confirming the presence of water, carbon monoxide, carbon dioxide, and methane. For HD 209458b, we confirm and constrain a thermal inversion in the dayside atmosphere. We also report detection of water, carbon monoxide, carbon dioxide, and methane on the dayside of HD 209458b. We report constraints due to individual data sets separately; a few key observations of HD 189733b made at similar wavelengths differ at the 2 σ level. We acknowledge the strong possibility that the atmosphere of HD 189733b is variable.
Madhusudhan Nikku
Seager Sara
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