A Systematic Retrieval Analysis of Secondary Eclipse Spectra Ii: a Uniform Analysis of Eight Planets and Their C to O Ratios

Secondary eclipse spectroscopy provides invaluable insights into the temperatures and compositions of exoplanetary atmospheres. We carry out a systematic temperature and abundance retrieval analysis of eight exoplanets (HD189733b, HD149026b, GJ436b, WASP-12b, WASP-19b, WASP-43b, TrES-2b, and TrES-3b) observed in secondary eclipse using a combination of spaceand ground-based facilities. Our goal with this analysis is to provide a consistent set of temperatures and compositions from which self-consistent models can be compared and to probe the underlying processes that shape these atmospheres. This paper is the second in a three part series of papers exploring the retrievability of temperatures and abundances from secondary eclipse spectra and the implications of these results for the chemistry of exoplanet atmospheres. In this investigation we present a catalogue of temperatures and abundances for H2O, CH4, CO, and CO2. We find that our temperatures and abundances are generally consistent with those of previous studies, although we do not find any convincing evidence for super-solar C to O ratios in any of the planets analyzed here. Furthermore, within our sample we find little evidence for thermal inversions over a wide range of effective temperatures, consistent with previous investigations. The lack of evidence for inversions over such a wide range of effective temperatures provides additional support for the hypothesis that TiO is unlikely to be the absorber responsible for the formation of these inversions.