Retrieval of Atmosphere Structure and Composition of Exoplanets from Transit Spectroscopy
Abstract
Recent spectroscopic observations of transiting exoplanets of HD 189733b, HD 209458b, GJ 436b and GJ 1214b provide the best chance of characterizing the thermal structure and composition of their atmospheres. Here we have applied an optimal estimation retrieval architecture to fit exoplanet spectra to determine the thermal structure and composition by solving the inverse problem. The development of a suite of radiative transfer and retrieval tools for exoplanet atmospheres is explained, building upon a rapid correlated-k approximation and a retrieval algorithm extensively used in our own solar system. With these tools we discuss the best-fitting spectrum to the measurements with the best-estimated solution (i.e. the maximum a posteriori solution) for the vertical temperature structure and molecular abundances. Additionally, the contribution functions and the vertical sensitivity to the molecules are fully utilized to interpret transmission and emission spectra, probing the structure and composition of the atmosphere. Furthermore, the analysis of the cross-correlation functions permits us to quantify the uncertainties in the degeneracy between the retrieved atmospheric properties based on the current quality of the data. This sheds light on the range of diverse interpretations offered by other studies so far. It also allows us to scrutinize further atmospheric features by maximizing the capability of the current retrieval algorithm and to demonstrate the benefit of using as broad a spectral range as possible, with clear implications for the next generation of exoplanetary missions.
- Publication:
-
American Astronomical Society Meeting Abstracts #219
- Pub Date:
- January 2012
- Bibcode:
- 2012AAS...21940502L