SSP seminar

New insights on exoplanet transmission spectroscopy with HST NICMOS & Ground-based transit photometry with ASTEP and XO-Constellation

Nicolas Crouzet (STScI)

Monday 25 February 2013, NOON
Pratt Conference Room, 60 Garden Street

Spectroscopy during planetary transits is a very powerful method for probing the atmosphere of exoplanets. The molecular composition and the presence of clouds and haze can be derived, providing clues on the chemical processes in the atmosphere. Some of the very first exoplanet spectra were obtained using NICMOS onboard HST. Features were identified in the spectra of several exoplanets, and attributed to molecules in their atmosphere. These breakthrough results have however 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. Uniquely for NICMOS exoplanet spectroscopy, the field of view of XO-2 contains not only the planet host star, but also a second star of very similar properties. This companion star is used as a benchmark, and yields the first estimate of residual noise in NICMOS exoplanet spectra. A similar analysis is performed for XO-1b, and the derived spectrum is compared to other published spectra. Then, I will talk about two projects dedicated to the search and characterization of transiting planets from the ground. I will show results from ASTEP (Antarctic Search for Transiting Exoplanets), which uses the continuous night and favorable atmospheric conditions of the Dome C site to perform visible photometry during the Antarctic winter. I will also present XO-Constellation, a network of small telescopes now observing from 3 different sites.


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