Name/Affiliation: Jacob Lustig-Yaeger (University of California, Santa Cruz)
On the Detection Significance of Molecules in Exoplanets from Secondary Eclipse Observations
Armed with a now sizable list of confirmed exoplanets we are beginning to face the big question of atmospheric characterization: What are these planets made of? Currently, only a few high-resolution spectroscopic observations have been performed to determine the atmospheric composition of transiting exoplanets, with most observations being broadband photometry. Moreover, previous claims of molecular detection in these atmospheres using broadband photometry are rightfully being called into question. We aim to assess the detection significance of molecules in the atmospheres of several exoplanets observed in secondary eclipse. We determine the detection significance with two Bayesian hypothesis testing procedures using two different widely used atmospheric retrieval approaches. We find that the detection of molecules with broadband ground-based and space-based photometry generally fails to breach 3-sigma confidence. We extend the study by estimating the molecular detection significance expected with the proposed FINESSE/SMEX mission. Our results suggest that it is rather difficult to make robust claims about the atmospheric composition of exoplanets observed in secondary eclipse with current telescopes. We suggest that dedicated high-resolution, high signal-to-noise instruments are the only sure avenue to convincingly detect molecules, and determine their abundances, in exoplanet atmospheres.