Cubillos, P and Harrington, J and Madhusudhan, N and Stevenson, KB and Hardy, RA and Blecic, J and Anderson, DR and Hardin, M and Campo, CJ (2013) WASP-8b: characterization of a cool and eccentric exoplanet with Spitzer. Astrophysical Journal, 768 (1). ISSN 0004-637X

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Abstract

WASP-8b has 2.18 times Jupiter's mass and is on an eccentric ($e=0.31$) 8.16-day orbit. With a time-averaged equilibrium temperature of 948 K, it is one of the least-irradiated hot Jupiters observed with the Spitzer Space Telescope. We have analyzed six photometric light curves of WASP-8b during secondary eclipse observed in the 3.6, 4.5, and 8.0 {\microns} Infrared Array Camera bands. The eclipse depths are $0.113\pm 0.018$%, $0.069\pm 0.007$%, and $0.093\pm 0.023$%, respectively, giving respective brightness temperatures of 1552, 1131, and 938 K. We characterized the atmospheric thermal profile and composition of the planet using a line-by-line radiative transfer code and a Markov-chain Monte Carlo sampler. The data indicated no thermal inversion, independently of any assumption about chemical composition. We noted an anomalously high 3.6-{\microns} brightness temperature (1552 K); by modeling the eccentricity-caused thermal variation, we found that this temperature is plausible for radiative time scales less than $\sim 10^{2}$ hours. However, as no model spectra fit all three data points well, the temperature discrepancy remains as an open question.

Item Type: Article
Additional Information: ©IOP Publishing, American Astronomical Society
Uncontrolled Keywords: planetary systems, stars: individual (WASP-8), techniques: photometric
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 14 Jul 2015 09:06
Last Modified: 25 May 2016 14:39
URI: http://eprints.keele.ac.uk/id/eprint/708

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