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Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra

Kammer, Joshua A. and Knutson, Heather A. and Line, Michael R. and Fortney, Jonathan J. and Deming, Drake and Burrows, Adam and Cowan, Nicolas B. and Triaud, Amaury H. M. J. and Agol, Eric and Désert, Jean-Michel and Fulton, Benjamin J. and Howard, Andrew W. and Laughlin, Gregory P. and Lewis, Nikole K. and Morley, Caroline V. and Moses, Julianne I. and Showman, Adam P. and Todorov, Kamen O. (2015) Spitzer Secondary Eclipse Observations of Five Cool Gas Giant Planets and Empirical Trends in Cool Planet Emission Spectra. Astrophysical Journal, 810 (2). Art. No. 118. ISSN 0004-637X.

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In this work we present Spitzer 3.6 and 4.5 μm secondary eclipse observations of five new cool (<1200 K) transiting gas giant planets: HAT-P-19b, WASP-6b, WASP-10b, WASP-39b, and WASP-67b. We compare our measured eclipse depths to the predictions of a suite of atmosphere models and to eclipse depths for planets with previously published observations in order to constrain the temperature- and mass-dependent properties of gas giant planet atmospheres. We find that the dayside emission spectra of planets less massive than Jupiter require models with efficient circulation of energy to the night side and/or increased albedos, while those with masses greater than that of Jupiter are consistently best-matched by models with inefficient circulation and low albedos. At these relatively low temperatures we expect the atmospheric CH_4/CO ratio to vary as a function of metallicity, and we therefore use our observations of these planets to constrain their atmospheric metallicities. We find that the most massive planets have dayside emission spectra that are best-matched by solar metallicity atmosphere models, but we are not able to place strong constraints on metallicities of the smaller planets in our sample. Interestingly, we find that the ratio of the 3.6 and 4.5 μm brightness temperatures for these cool transiting planets is independent of planet temperature, and instead exhibits a tentative correlation with planet mass. If this trend can be confirmed, it would suggest that the shape of these planets' emission spectra depends primarily on their masses, consistent with the hypothesis that lower-mass planets are more likely to have metal-rich atmospheres.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kammer, Joshua A.0000-0002-3441-3757
Knutson, Heather A.0000-0002-0822-3095
Line, Michael R.0000-0002-2338-476X
Fortney, Jonathan J.0000-0002-9843-4354
Deming, Drake0000-0001-5727-4094
Burrows, Adam0000-0002-3099-5024
Cowan, Nicolas B.0000-0001-6129-5699
Triaud, Amaury H. M. J.0000-0002-5510-8751
Agol, Eric0000-0002-0802-9145
Désert, Jean-Michel0000-0002-0875-8401
Fulton, Benjamin J.0000-0003-3504-5316
Howard, Andrew W.0000-0001-8638-0320
Laughlin, Gregory P.0000-0002-3253-2621
Lewis, Nikole K.0000-0002-8507-1304
Morley, Caroline V.0000-0002-4404-0456
Moses, Julianne I.0000-0002-8837-0035
Todorov, Kamen O.0000-0002-9276-8118
Additional Information:© 2015 American Astronomical Society. Received 2015 May 13; accepted 2015 July 31; published 2015 September 4. J.-M.D. and N.K.L. acknowledge funding from NASA through the Sagan Exoplanet Fellowship program administered by the NASA Exoplanet Science Institute (NExScI). 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 contract with NASA.
Funding AgencyGrant Number
Subject Keywords:eclipses, planetary systems, techniques: photometric
Issue or Number:2
Record Number:CaltechAUTHORS:20151027-100907704
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61551
Deposited By: Ruth Sustaita
Deposited On:27 Oct 2015 18:56
Last Modified:06 Nov 2019 18:08

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