The mid-infrared spectrum of the transiting exoplanet HD 209458b

Abstract

We report the spectroscopic detection of mid-infrared emission from the transiting exoplanet HD 209458b. Using archive data taken with the Spitzer/IRS instrument, we have determined the spectrum of HD 209458b between 7.46 and 15.25 microns. We have used two independent methods to determine the planet spectrum, one differential in wavelength and one absolute, and find the results are in good agreement. Over much of this spectral range, the planet spectrum is consistent with featureless thermal emission. Between 7.5 and 8.5 microns, we find evidence for an unidentified spectral feature. If this spectral modulation is due to absorption, it implies that the dayside vertical temperature profile of the planetary atmosphere is not entirely isothermal. Using the IRS data, we have determined the broad-band eclipse depth to be 0.00315 +/- 0.000315, implying significant redistribution of heat from the dayside to the nightside. This work required development of improved methods for Spitzer/IRS data calibration that increase the achievable absolute calibration precision and dynamic range for observations of bright point sources.

35 pages, 12 figures, revised version accepted by the Astrophysical Journal

References in corpus (9)

• Detection of Thermal Emission from an Extrasolar Planet
• Using Stellar Limb-Darkening to Refine the Properties of HD 209458b
• The phase-dependent Infrared brightness of the extrasolar planet upsilon Andromedae b
• Strong Infrared Emission from the Extrasolar Planet HD189733b
• A Spectrum of an Extrasolar Planet
• Theory for the Secondary Eclipse Fluxes, Spectra, Atmospheres, and Light Curves of Transiting Extrasolar Giant Planets
• Binarity as a key factor in protoplanetary disk evolution: Spitzer disk census of the eta Chamaeleontis cluster
• A Sensitive Search for Variability in Late L Dwarfs: The Quest for Weather
• IRS Spectra of Solar-Type Stars: \break A Search for Asteroid Belt Analogs

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• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing
• Dust in Brown Dwarfs and Extra-solar Planets I. Chemical composition and spectral appearance of quasi-static cloud layers
• Optical Albedo Theory of Strongly-Irradiated Giant Planets: The Case of HD 209458b
• MBM 12: young protoplanetary discs at high galactic latitude
• Emergent Exoplanet Flux: Review of the Spitzer Results