Infrared Spectroscopy of the Exoplanets CoRoT-2b, XO-1b, HD 209458b Using the Wide-Field Camera-3 On the Hubble Space Telescope

Abstract

Exoplanetary transmisison spectroscopy requires exquisite precision of measurement. Due to telluric water vapor,reliable detections of water vapor in exoplanets is practical only with space-based instruments, such as the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). With this work, we present HST WFC3 grism spectroscopy of two hot Jupiters, HD209458b and XO-1b in transit, and one very hot Jupiter, CoRoT-2b, in secondary eclipse, in the wavelength range of 1.1-1.7μm. We search for water absorption or emission in the infrared spectra of these exoplanetary atmospheres. Until recently, results from observations in other infrared bands using both space-based and ground-based telescopes have given either conflicting results, due to differing analysis methodologies, or unclear results, due to model degeneracies left unbroken by insufficient data. Our new high-precision spectra, using WFC3 in both spatial-scan and non-scan mode, resolve some of these ambiguities.