astro-ph/0702494
Date: Mon, 19 Feb 2007 21:00:26 GMT (175kb)
A Spitzer Spectrum of the Exoplanet HD 189733b
Authors: C. J. Grillmair (1), D. Charbonneau (2), A. Burrows (3), L. Armus (1), J. Stauffer (1), V. Meadows (1), J. van Cleve (4), D. Levine (1) ((1) Spitzer Science Center, (2) Harvard-Smithsonian Center for Astrophysics, (3) Steward Observatory, (4) Ball Aerospace and Technologies Corp.)
Comments: 12 pages, 3 figures, accepted for publication in the Astrophysical Journal Letters
We report on the measurement of the 7.5-14.7 micron spectrum for the transiting extrasolar giant planet HD 189733b using the Infrared Spectrograph on the Spitzer Space Telescope. Though the observations comprise only 12 hours of telescope time, the continuum is well measured and has a flux ranging from 0.6 mJy to 1.8 mJy over the wavelength range, or 0.49 +/- 0.02% of the flux of the parent star.
The variation in the measured fractional flux is very nearly flat over the entire wavelength range and shows no indication of significant absorption by water or methane, in contrast with the predictions of most atmospheric models. Models with strong day/night differences appear to be disfavored by the data, suggesting that heat redistribution to the night side of the planet is highly efficient.
