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Detection of a westward hotspot offset in the atmosphere of hot gas giant CoRoT-2b

Dang, Lisa and Cowan, Nicolas B. and Schwartz, Joel C. and Rauscher, Emily and Zhang, Michael and Knutson, Heather A. and Line, Michael and Dobbs-Dixon, Ian and Deming, Drake and Sundararajan, Sudarsan and Fortney, Jonathan J. and Zhao, Ming (2018) Detection of a westward hotspot offset in the atmosphere of hot gas giant CoRoT-2b. Nature Astronomy, 2 (3). pp. 220-227. ISSN 2397-3366. http://resolver.caltech.edu/CaltechAUTHORS:20171127-113258670

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Abstract

Short-period planets exhibit day–night temperature contrasts of hundreds to thousands of kelvin. They also exhibit eastward hotspot offsets whereby the hottest region on the planet is east of the substellar point; this has been widely interpreted as advection of heat due to eastward winds2. We present thermal phase observations of the hot Jupiter CoRoT-2b obtained with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. These measurements show the most robust detection to date of a westward hotspot offset of 23 ± 4°, in contrast with the nine other planets with equivalent measurements. The peculiar infrared flux map of CoRoT-2b may result from westward winds due to non-synchronous rotation or magnetic effects, or partial cloud coverage, that obscure the emergent flux from the planet’s eastern hemisphere. Non-synchronous rotation and magnetic effects may also explain the planet’s anomalously large radius. On the other hand, partial cloud coverage could explain the featureless dayside emission spectrum of the planet. If CoRoT-2b is not tidally locked, then it means that our understanding of star–planet tidal interaction is incomplete. If the westward offset is due to magnetic effects, our result represents an opportunity to study an exoplanet’s magnetic field. If it has eastern clouds, then it means that a greater understanding of large-scale circulation on tidally locked planets is required.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1038/s41550-017-0351-6DOIArticle
https://www.nature.com/articles/s41550-017-0351-6PublisherArticle
http://rdcu.be/FZRGPublisherFree ReadCube access
https://arxiv.org/abs/1801.06548arXivDiscussion Paper
ORCID:
AuthorORCID
Dang, Lisa0000-0003-4987-6591
Cowan, Nicolas B.0000-0001-6129-5699
Schwartz, Joel C.0000-0001-5232-9957
Zhang, Michael0000-0002-0659-1783
Knutson, Heather A.0000-0002-0822-3095
Line, Michael0000-0002-2338-476X
Deming, Drake0000-0001-5727-4094
Fortney, Jonathan J.0000-0002-9843-4354
Zhao, Ming0000-0002-4258-9517
Additional Information:© 2018 Macmillan Publishers Limited, part of Springer Nature. Received: 15 August 2017; Accepted: 28 November 2017; Published online: 22 January 2018. L.D. thanks S. Carey, J. Ingalls and W. Glaccum from the Spitzer IRAC team for the helpful discussions that contributed to the reduction of the data. Funding for this work was provided in part by the Natural Sciences and Engineering Research Council of Canada (NSERC) discovery grant and the California Institute of Technology’s Infrared Processing and Analysis Center (Caltech/IPAC) Visiting Graduate Research Fellowship. Work by S.S. was funded by the Google Summer of Code programme. 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. Author Contributions: L.D. extracted the photometric measurements from the data, detrended the data, developed and fit the phase curve models, led the analysis and wrote the manuscript. N.B.C. is the prinicpal investigator of the successful Spitzer proposal from which we obtained the observations and contributed to the writing of the manuscript. J.C.S. contributed materials to the main text. E.R. contributed to the interpretation for the results and to the discussion. M.Z. and H.A.K. verified the robustness of the analysis and contributed to the interpretation of results. S.S. contributed to the photometric measurements pipeline. J.C.S., E.R., H.A.K., I.D.-D., M.L., D.D., J.J.F. and M.Z. are co-investigators of the successful Spitzer proposal from which we obtained the observations. All authors commented on the manuscript. The authors declare no competing financial interests.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
GoogleUNSPECIFIED
NASA/JPL/CaltechUNSPECIFIED
Record Number:CaltechAUTHORS:20171127-113258670
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171127-113258670
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83441
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:27 Nov 2017 19:36
Last Modified:02 Mar 2018 21:15

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