Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab

摘要

We describe the detection of water vapor in the atmosphere of the transiting hot Jupiter KELT-2Ab by treating thestar–planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve thesignal of the planet’s motion with deep combined flux observations of the star and the planet. In total, six epochs ofKeck NIRSPEC L-band observations were obtained, and the full data set was subjected to a cross-correlationanalysis with a grid of self-consistent atmospheric models. We measure a radial projection of the Keplerianvelocity, K P , of 148?±?7kms ?1 , consistent with transit measurements, and detect water vapor at 3.8σ. Wecombine NIRSPEC L-band data with Spitzer IRAC secondary eclipse data to further probe the metallicity andcarbon-to-oxygen ratio of KELT-2Ab’s atmosphere. While the NIRSPEC analysis provides few extra constraintson the Spitzer data, it does provide roughly the same constraints on metallicity and carbon-to-oxygen ratio. Thisbodes well for future investigations of the atmospheres of non-transiting hot Jupiters.