CfA OIR Division Lunch Talks
Wednesday, January 29, 2014, 11:00 am, Pratt Conference Room

Clouds and Haze in the Atmosphere
of the Super-Earth Gj1214b
Using the Spitzer Space Telescope

Jonathan Fraine
(University of Maryland/Pontificia Universidad Católica de Chile)

Intense efforts to measure molecular absorption in the atmospheres of smaller planets during transit have revealed only featureless spectra. Several teams investigated the transmission spectrum for the transiting Super-Earth GJ1214b, but found no significant spectral features. We observed GJ1214b during a 20-day quasi-continuous sequence in May 2011, using Warm Spitzer at 4.5 #m wavelength. The goals of our long observation were to accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We analyzed 14 transits of GJ1214b at 4.5 #m, 3 transits at 3.6 #m, and 7 new ground-based transits in the I+z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows (2012). Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, in conjunction with recently published Kreidberg et al. (2014) HST-WFC3 flat spectrum, the best-fit model for the atmosphere is a non-detection, or a flat line. The implication for the atmosphere of GJ 1214b is that optically thick clouds obscure even the longest wavelength observations aimed at revealing its composition.

Phased and binned transit of GJ1214b at 4.5μm from 13 Spitzer transits,
plus the transit observed by Désert et al. (2011)