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Published February 1, 2014 | Submitted + Published
Journal Article Open

Warm Spitzer and Palomar Near-IR Secondary Eclipse Photometry of Two Hot Jupiters: WASP-48b and HAT-P-23b

Abstract

We report secondary eclipse photometry of two hot Jupiters, WASP-48b and HAT-P-23b, at 3.6 and 4.5 μm taken with the InfraRed Array Camera aboard the Spitzer Space Telescope during the warm Spitzer mission and in the H and K_S bands with the Wide Field IR Camera at the Palomar 200 inch Hale Telescope. WASP-48b and HAT-P-23b are Jupiter-mass and twice Jupiter-mass objects orbiting an old, slightly evolved F star and an early G dwarf star, respectively. In the H, K_S , 3.6 μm, and 4.5 μm bands, respectively, we measure secondary eclipse depths of 0.047% ± 0.016%, 0.109% ± 0.027%, 0.176% ± 0.013%, and 0.214% ± 0.020% for WASP-48b. In the K_S , 3.6 μm, and 4.5 μm bands, respectively, we measure secondary eclipse depths of 0.234% ± 0.046%, 0.248% ± 0.019%, and 0.309% ± 0.026% for HAT-P-23b. For WASP-48b and HAT-P-23b, respectively, we measure delays of 2.6 ± 3.9 minutes and 4.0 ± 2.4 minutes relative to the predicted times of secondary eclipse for circular orbits, placing 2σ upper limits on |ecos ω| of 0.0053 and 0.0080, both of which are consistent with circular orbits. The dayside emission spectra of these planets are well-described by blackbodies with effective temperatures of 2158 ± 100 K (WASP-48b) and 2154 ± 90 K (HAT-P-23b), corresponding to moderate recirculation in the zero albedo case. Our measured eclipse depths are also consistent with one-dimensional radiative transfer models featuring varying degrees of recirculation and weak thermal inversions or no inversions at all. We discuss how the absence of strong temperature inversions on these planets may be related to the activity levels and metallicities of their host stars.

Additional Information

© 2014 American Astronomical Society. Received 2013 September 29; accepted 2013 December 10; published 2014 January 15. J.G.O. receives support from the National Science Foundation's Graduate Research Fellowship Program and thanks Michael Line for many helpful discussions. J.-M.D. acknowledges funding from NASA through the Sagan Exoplanet Fellowship program administered by the NASA Exoplanet Science Institute (NExScI). M.Z. is supported by the Center for Exoplanets and Habitable Worlds at Penn State University, and the AAS Small Research Grant. 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. The Palomar Hale Telescope is operated by Caltech, JPL, and Cornell University.

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Published - 0004-637X_781_2_109.pdf

Submitted - 1310.0011v1.pdf

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Additional details

Created:
August 22, 2023
Modified:
February 2, 2024