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

Cited by in corpus (25)

• The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b
• Strong Water Absorption in the Dayside Emission Spectrum of the Planet HD 189733b
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• A chemical model for the atmosphere of hot Jupiters
• 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
• The 4.5 $\mu$m full-orbit phase curve of the hot Jupiter HD 209458b
• New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b
• The UK Met Office GCM with a sophisticated radiation scheme applied to the hot Jupiter HD 209458b
• The Earliest Phases of Star formation observed with Herschel (EPoS): The dust temperature and density distributions of B68
• Optical Albedo Theory of Strongly-Irradiated Giant Planets: The Case of HD 209458b
• Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
• Updated Spitzer Emission Spectroscopy of Bright Transiting Hot Jupiter HD189733b
• Observability of signatures of transport-induced chemistry in clear atmospheres of hot gas giant exoplanets
• Impact of photochemical hazes and gases on exoplanet atmospheric thermal structure
• The ground-based H, K, and L-band absolute emission spectra of HD 209458b
• MBM 12: young protoplanetary discs at high galactic latitude
• On spectroscopic phase-curve retrievals: H2 dissociation and thermal inversion in the atmosphere of the ultra-hot Jupiter WASP-103 b
• Spectral evolution and radial dust transport in the prototype young eruptive system EX Lup
• Time Resolved Absorption of Six Chemical Species With MAROON-X Points to Strong Drag in the Ultra Hot Jupiter TOI-1518 b
• ISM Dust Grains and N-band Spectral Variability in the Spatially Resolved Subarcsecond Binary UY Aur
• A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History
• Emergent Exoplanet Flux: Review of the Spitzer Results
• Fundamental Challenges to Remote Sensing of Exo-Earths
• Generation of an optimal target list for the Exoplanet Characterisation Observatory (EChO)