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Spitzer Transits of the Super-Earth GJ1214b and Implications for its Atmosphere

Fraine, Jonathan D. and Deming, Drake and Gillon, Michaël and Jehin, Emmanuël and Demory, Brice-Olivier and Benneke, Bjoern and Seager, Sara and Lewis, Nikole K. and Knutson, Heather and Désert, Jean-Michel (2013) Spitzer Transits of the Super-Earth GJ1214b and Implications for its Atmosphere. Astrophysical Journal, 765 (2). Art. No. 127. ISSN 0004-637X.

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We observed the transiting super-Earth exoplanet GJ1214b using warm Spitzer at 4.5 μm wavelength during a 20 day quasi-continuous sequence in 2011 May. 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 here report results from the transit monitoring of GJ1214b, including a reanalysis of previous transit observations by Désert et al. In total, we analyze 14 transits of GJ1214b at 4.5 μm, 3 transits at 3.6 μm, 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. Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I+z, we evaluate models from Benneke & Seager and Howe & Burrows using a χ^2 analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelengths due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the Howe & Burrows tholin-haze model remains the best fit, even when systematic differences among observers are considered.

Item Type:Article
Related URLs:
URLURL TypeDescription
Fraine, Jonathan D.0000-0003-0910-5805
Deming, Drake0000-0001-5727-4094
Gillon, Michaël0000-0003-1462-7739
Demory, Brice-Olivier0000-0002-9355-5165
Benneke, Bjoern0000-0001-5578-1498
Seager, Sara0000-0002-6892-6948
Lewis, Nikole K.0000-0002-8507-1304
Knutson, Heather0000-0002-0822-3095
Désert, Jean-Michel0000-0002-0875-8401
Additional Information:© 2013 American Astronomical Society. Received 2012 October 2; accepted 2013 January 24; published 2013 February 26. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. We thank the Spitzer staff for their hard work and dedication in implementing these difficult observations, and the anonymous referee for a careful review of this paper.
Funding AgencyGrant Number
Subject Keywords:infrared: planetary systems; planets and satellites: atmospheres; planets and satellites: composition; techniques: photometric
Issue or Number:2
Record Number:CaltechAUTHORS:20130408-075625993
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Official Citation:Spitzer Transits of the Super-Earth GJ1214b and Implications for its Atmosphere Jonathan D. Fraine et al. 2013 ApJ 765 127
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37796
Deposited By: Ruth Sustaita
Deposited On:08 Apr 2013 15:22
Last Modified:11 Oct 2019 23:10

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