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The 4.5 μm Full-orbit Phase Curve of the Hot Jupiter HD 209458b

Zellem, Robert T. and Lewis, Nikole K. and Knutson, Heather A. and Griffith, Caitlin A. and Showman, Adam P. and Fortney, Jonathan J. and Cowan, Nicolas B. and Agol, Eric and Burrows, Adam and Charbonneau, David and Deming, Drake and Laughlin, Gregory and Langton, Jonathan (2014) The 4.5 μm Full-orbit Phase Curve of the Hot Jupiter HD 209458b. Astrophysical Journal, 790 (1). Art. No. 53. ISSN 0004-637X. doi:10.1088/0004-637X/790/1/53.

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The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by ~35% to 0.1391%^(+0.0072%)_(-0.0069%), changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40°.9 ± 6°.0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (T_(bright) = 1499 ± 15 K) and nightside (T_(bright) = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH4 line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Zellem, Robert T.0000-0001-7547-0398
Lewis, Nikole K.0000-0002-8507-1304
Knutson, Heather A.0000-0002-0822-3095
Fortney, Jonathan J.0000-0002-9843-4354
Cowan, Nicolas B.0000-0001-6129-5699
Agol, Eric0000-0002-0802-9145
Burrows, Adam0000-0002-3099-5024
Charbonneau, David0000-0002-9003-484X
Deming, Drake0000-0001-5727-4094
Laughlin, Gregory0000-0002-3253-2621
Additional Information:© 2014 The American Astronomical Society. Received 2014 March 20; accepted 2014 June 2; published 2014 July 2. R.Z. and C.A.G. are supported by the NASA Planetary Atmospheres Program. N.K.L. performed this work in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. A.P.S. is supported by the NASA Origins program. R.Z. would like to thank Travis Barman, Ian J. M. Crossfield, Julien de Wit, Davin Flateau, Joe Giacalone, Tiffany Kataria, Michael R. Line, Julianne I. Moses, Kyle A. Pearson, Emily Rauscher, Tamara M. Rogers, David K. Sing, and Mark R. Swain for their helpful discussions. We would like to thank the two referees for their helpful comments and suggestions.
Funding AgencyGrant Number
Subject Keywords:atmospheric effects; methods: numerical; planets and satellites: general; planets and satellites: individual (HD 209458b); techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20140818-092028974
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Official Citation:The 4.5 μm Full-orbit Phase Curve of the Hot Jupiter HD 209458b Robert T. Zellem et al. 2014 ApJ 790 53
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48644
Deposited By: Jason Perez
Deposited On:19 Aug 2014 21:55
Last Modified:10 Nov 2021 18:33

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