Authors

K. B. Stevenson; J. Harrington; J. J. Fortney; T. J. Loredo; R. A. Hardy; S. Nymeyer; W. C. Bowman; P. Cubillos; M. O. Bowman;M. Hardin

Comments

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Abbreviated Journal Title

Astrophys. J.

Keywords

planetary systems; stars: individual (HD 149026); techniques:; photometric; SPITZER-SPACE-TELESCOPE; 8 MU-M; THERMAL EMISSION; GIANT PLANETS; HOT; JUPITERS; EXTRASOLAR PLANET; SPECTRAL MODELS; LIGHT CURVES; GJ 436B; ATMOSPHERES; Astronomy & Astrophysics

Abstract

The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on 11 secondary-eclipse events at 3.6, 4.5, 3 x 5.8, 4 x 8.0, and 2 x 16 mu m plus three primary-transit events at 8.0 mu m. The eclipse depths from jointly fit models at each wavelength are 0.040% +/- 0.003% at 3.6 mu m, 0.034% +/- 0.006% at 4.5 mu m, 0.044% +/- 0.010% at 5.8 mu m, 0.052% +/- 0.006% at 8.0 mu m, and 0.085% +/- 0.032% at 16 mu m. Multiple observations at the longer wavelengths improved eclipse-depth signal-to-noise ratios by up to a factor of two and improved estimates of the planet-to-star radius ratio (R-p/R star = 0.0518 +/- 0.0006). We also identify no significant deviations from a circular orbit and, using this model, report an improved period of 2.8758916 +/- 0.0000014 days. Chemical-equilibrium models find no indication of a temperature inversion in the dayside atmosphere of HD 149026b. Our best-fit model favors large amounts of CO and CO2, moderate heat redistribution (f = 0.5), and a strongly enhanced metallicity. These analyses use BiLinearly-Interpolated Subpixel Sensitivity (BLISS) mapping, a new technique to model two position-dependent systematics (intrapixel variability and pixelation) by mapping the pixel surface at high resolution. BLISS mapping outperforms previous methods in both speed and goodness of fit. We also present an orthogonalization technique for linearly correlated parameters that accelerates the convergence of Markov chains that employ the etropolis random walk sampler. The electronic supplement contains light-curve files.

Journal Title

Astrophysical Journal

Volume

754

Issue/Number

2

Publication Date

1-1-2012

Document Type

Article

Language

English

First Page

23

WOS Identifier

WOS:000306666700057

ISSN

0004-637X

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