Spectroscopic observations of hot-Jupiters with Hubble Space Telescope NICMOS and WFC3

Séminaire IPAG de Nicolas Crouzet (STScI), jeudi 6 février 2014 à 11h00, IPAG seminar room

Spectroscopy during transits and eclipses is a very powerful method to probe the atmosphere of exoplanets. Crucial properties such as the molecular composition, the presence of clouds, and the pressure-temperature profile can be derived. Some of the very first exoplanet spectra were obtained using NICMOS onboard HST. Features were identified in the spectra of several hot-Jupiters and attributed to molecular species in their atmosphere. However, these breakthrough discoveries have been subject to strong controversy in the exoplanet community. In this talk, I will present the analysis of the gas giant planets XO-2b and XO-1b observed with NICMOS. This yields the first estimate of residual noise in NICMOS exoplanet spectra, and sheds new light on previous discoveries. The Wide Field Camera 3 (WFC3) on board HST now delivers hot-Jupiter spectra with much higher fidelity than NICMOS had in the past. I will present the observations of the canonical hot-Jupiter HD 189733b with WFC3 in the bandpass 1.1 to 1.7 microns during a transit and during an eclipse, using the newly implemented spatial scanning mode. This mode largely increases the number of collected photons compared to the staring mode, and produces satisfactory results even with a straight-forward analysis. I will discuss the amplitude of absorption and emission features seen in the spectra, and the inferred atmospheric properties for HD 189733b.