High-precision eclipse spectrophotometry of transiting terrestrial exoplanets represents a promising path for the first atmospheric characterizations of habitable worlds and the search for life outside our solar system.
The detection of terrestrial planets transiting nearby late-type M-dwarfs could make this approach applicable within the next decade, with near-to-come general facilities. In this context, we previously identified GJ 1214 as a high-priority target for a transit search, as the transit probability of a habitable planet orbiting this nearby M4.5 dwarf would be significantly enhanced by the transiting nature of GJ 1214 b, the super-Earth already known to orbit the star.
Basing on this observation, we have set-up an ambitious high-precision photometric monitoring of GJ 1214 with the Spitzer Space Telescope to probe its entire habitable zone in search of a transiting planet as small as Mars. We present here the results of this transit search. Unfortunately, we did not detect any second transiting planet. Assuming GJ 1214 hosts a habitable planet larger than Mars, our global analysis of the whole Spitzer dataset leads to a posterior no-transit probability >=97%.
Our analysis allows us to significantly improve the characterization of GJ 1214 b, to measure its occultation depth to be 70+-35 ppm at 4.5 microns, and to constrain it to be smaller than 205ppm (3-sigma upper limit) at 3.6 microns. In agreement with the plethora of transmission measurements published so far for GJ 1214 b, these emission measurements are consistent with both a metal-rich and a cloudy hydrogen-rich atmosphere.
M. Gillon, B.-O. Demory, N. Madhusudhan, D. Deming, S. Seager, H. A. Knutson, A. Lanotte, X. Bonfils, J.-M. Desert, L. Delrez, E. Jehin, J. D. Fraine, P. Magain, A. H. M. J. Triaud (Submitted on 25 Jul 2013)
Comments: 13 pages, 10 figures. Submitted to A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1307.6722 [astro-ph.EP]
(or arXiv:1307.6722v1 [astro-ph.EP] for this version) Submission history From: Michael Gillon [view email] [v1] Thu, 25 Jul 2013 12:42:18 GMT (1370kb)
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