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Statistical Characterization of Hot Jupiter Atmospheres using Spitzer's Secondary Eclipses

Garhart, Emily and Deming, Drake and Mandell, Avi and Knutson, Heather A. and Wallack, Nicole and Burrows, Adam and Fortney, Jonathan J. and Hood, Callie and Seay, Christopher and Sing, David K. and Benneke, Björn and Fraine, Jonathan D. and Kataria, Tiffany and Lewis, Nikole and Madhusudhan, Nikku and McCullough, Peter and Stevenson, Kevin B. and Wakeford, Hannah (2020) Statistical Characterization of Hot Jupiter Atmospheres using Spitzer's Secondary Eclipses. Astronomical Journal, 159 (4). Art. No. 137. ISSN 1538-3881. doi:10.3847/1538-3881/ab6cff.

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We report 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed at 3.6 and 4.5 μm using the Spitzer Space Telescope. Our eclipse results for 27 of these planets are new, and include highly irradiated worlds such as KELT-7b, WASP-87b, WASP-76b, and WASP-64b, and important targets for James Webb Space Telescope such as WASP-62b. We find that WASP-62b has a slightly eccentric orbit (e cos ω = 0.00614±0.00064), and we confirm the eccentricity of HAT-P-13b and WASP-14b. The remainder are individually consistent with circular orbits, but we find statistical evidence for eccentricity increasing with orbital period in our range from 1 to 5 days. Our day-side brightness temperatures for the planets yield information on albedo and heat redistribution, following Cowan & Agol (2011). Planets having maximum day-side temperatures exceeding ~2200 K are consistent with having zero albedo and a distribution of stellar irradiance uniformly over the day-side hemisphere. Our most intriguing result is that we detect a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 100 ± 24 parts-per-million per Kelvin, over the entire temperature range in our sample (800–2500 K). No existing model predicts this trend over such a large range of temperature. We suggest that this may be due to a structural difference in the atmospheric temperature profiles of real planetary atmospheres as compared to models.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Deming, Drake0000-0001-5727-4094
Mandell, Avi0000-0002-8119-3355
Knutson, Heather A.0000-0002-0822-3095
Wallack, Nicole0000-0003-0354-0187
Burrows, Adam0000-0002-3099-5024
Fortney, Jonathan J.0000-0002-9843-4354
Sing, David K.0000-0001-6050-7645
Benneke, Björn0000-0001-5578-1498
Fraine, Jonathan D.0000-0003-0910-5805
Kataria, Tiffany0000-0003-3759-9080
Lewis, Nikole0000-0002-8507-1304
Madhusudhan, Nikku0000-0002-4869-000X
McCullough, Peter0000-0001-9165-9799
Stevenson, Kevin B.0000-0002-7352-7941
Wakeford, Hannah0000-0003-4328-3867
Additional Information:© 2020 The American Astronomical Society. Received 2019 January 19; revised 2019 November 8; accepted 2020 January 15; published 2020 February 28. We thank the staff of the Spitzer Space Telescope for their help in planning and their careful scheduling and execution of the observations. We also thank an anonymous referee and the statistical editor for comments that significantly improved this paper. This work was supported by NASA ADAP grant NNX16AF34G.
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:Exoplanet astronomy; Exoplanet atmospheres
Issue or Number:4
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Exoplanet atmospheres (487)
Record Number:CaltechAUTHORS:20190124-122555938
Persistent URL:
Official Citation:Emily Garhart et al 2020 AJ 159 137
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92456
Deposited By: George Porter
Deposited On:25 Jan 2019 16:20
Last Modified:16 Nov 2021 03:50

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