We estimate flux ratios of the extrasolar planet XO-1b to its host star XO-1 at 3.6, 4.5, 5.8 and 8.0 microns with the IRAC on the Spitzer Space Telescope to be 0.00086 +/- 0.00007, 0.00122 +/- 0.00009, 0.00261 +/- 0.00031 and 0.00210 +/- 0.00029, respectively. The fluxes are inconsistent with a canonical cloudless model for the thermal emission from a planet and suggest an atmosphere with a thermal inversion layer and a possible stratospheric absorber. A newly emerging correlation between the presence of a thermal inversion layer in the planetary atmosphere and stellar insolation of the planet (Burrows et al. 2007b) is refined. The sub-stellar point flux from the parent star at XO-1b of ~ 0.49 x 10^9 erg cm^-2 s^-1 sets a new lower limit for the occurrence of a thermal inversion in a planetary atmosphere.
@article{arxiv.0805.2418,
title = {Thermal Emission of Exoplanet XO-1b},
author = {Pavel Machalek and Peter R. McCullough and Christopher J. Burke and Jeff A. Valenti and Adam Burrows and Joseph L. Hora},
journal= {arXiv preprint arXiv:0805.2418},
year = {2008}
}
Comments
7 pages, 4 figures, 2 tables, accepted for publication to ApJ