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Primary transit of the planet HD 189733b at 3.6 and 5.8 µm

Beaulieu, J. P. and Carey, S. and Ribas, I and Tinetti, G. (2008) Primary transit of the planet HD 189733b at 3.6 and 5.8 µm. Astrophysical Journal, 677 (2). pp. 1343-1347. ISSN 0004-637X.

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The hot Jupiter HD 189733b was observed during its primary transit using the Infrared Array Camera on the Spitzer Space Telescope. The transit depths were measured simultaneously at 3.6 and 5.8 μm. Our analysis yields values of 2:356% ± 0:019% and 2:436% ± 0:020% at 3.6 and 5.8 μm, respectively, for a uniform source. We estimated the contribution of the limb-darkening and starspot effects on the final results. We concluded that although the limb darkening increases by ~0.02%–0.03% the transit depths, the differential effects between the two IRAC bands is even smaller, 0.01%. Furthermore, the host star is known to be an active spotted K star with observed photometric modulation. If we adopt an extreme model of 20% coverage with spots 1000 K cooler of the star surface, it will make the observed transits shallower by 0.19% and 0.18%. The difference between the two bands will be only of 0.01%, in the opposite direction to the limb-darkening correction. If the transit depth is affected by limb darkening and spots, the differential effects between the 3.6 and 5.8 μm bands are very small. The differential transit depths at 3.6 and 5.8 μm and the recent one published by Knutson and coworkers) at 8 μm are in agreement with the presence of water vapor in the upper atmosphere of the planet. This is the companion paper to Tinetti et al., where the detailed atmosphere models are presented.

Item Type:Article
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Beaulieu, J. P.0000-0003-0014-3354
Carey, S.0000-0002-0221-6871
Additional Information:© 2008. The American Astronomical Society. Received 2007 August 21; accepted 2007 November 21; published 2008 April 20. We thank the staff at the Spitzer Science Center for their help. We are very grateful to Christophe Alard for having helped us in the data reduction phases of Spitzer data. His optimal centroid determination has been an important contribution to this analysis. We thank David Kipping for careful reading of the manuscript, and David Sing for providing the limb-darkening coefficients. 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. G. Tinetti acknowledge the support of the European Space Agency. I.R. acknowledges support from the Spanish Ministerio de Educación y Ciencia via grant AYA2006-15623-C02-02. J.P.B., I.R., and G.T. acknowledge the financial support of the ANR HOLMES. Facilities: Spitzer. Online material: color figure
Funding AgencyGrant Number
European Space Agency (ESA)UNSPECIFIED
Ministerio de Educación y Ciencia (MEC)AYA2006-15623-C02-02
Agence Nationale pour la Recherche (ANR)UNSPECIFIED
Subject Keywords:planetary systems — planetary systems: formation
Issue or Number:2
Record Number:CaltechAUTHORS:BEAapj08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12630
Deposited By: Marie Noren
Deposited On:09 Jan 2009 04:51
Last Modified:09 Mar 2020 13:18

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