Theoretical spectra and light curves of close-in extrasolar giant planets and comparison with data

A. Burrows, J. Budaj, Ivan - Hubeny

Research output: Contribution to journalArticle

202 Citations (Scopus)

Abstract

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which Spitzer planet/star contrast ratios or light curves have been published (circa 2007 June). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and u And b. By comparing models with data, we find that a number of EGP atmospheres experience thermal inversions and have stratospheres. This is particularly true for HD 209458b, HD 149026b, and u And b. This finding translates into qualitative changes in the planet/star contrast ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover, the presence of atmospheric water in abundance is fully consistent with all the Spitzer data for the measured planets. For planets with stratospheres, water absorption features invert into emission features and mid-infrared fluxes can be enhanced by a factor of 2. In addition, the character of near-infrared planetary spectra can be radically altered. We derive a correlation between the importance of such stratospheres and the stellar flux on the planet, suggesting that close-in EGPs bifurcate into two groups: those with and without stratospheres. From the finding that TrES-1 shows no signs of a stratosphere, while HD 209458b does, we estimate the magnitude of this stellar flux breakpoint. We find that the heat redistribution parameter, Pn, for the family of close-in EGPs assumes values from ∼0.1 to ∼0.4. This paper provides a broad theoretical context for the future direct characterization of EGPs in tight orbits around their illuminating stars.

Original languageEnglish (US)
Pages (from-to)1436-1457
Number of pages22
JournalAstrophysical Journal
Volume678
Issue number2
DOIs
StatePublished - May 10 2008

Fingerprint

light curve
planets
planet
curves
stratosphere
stars
comparison
atmospheres
atmosphere
eclipses
illuminating
water
near infrared
irradiation
inversions
orbits
orbitals
heat
estimates

Keywords

  • Planetary systems
  • Planets and satellites: general
  • Stars: individual (HD 209458, HD 189733, TrES-1, HD 149026, u Andromedae, HD 179949)

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Theoretical spectra and light curves of close-in extrasolar giant planets and comparison with data. / Burrows, A.; Budaj, J.; Hubeny, Ivan -.

In: Astrophysical Journal, Vol. 678, No. 2, 10.05.2008, p. 1436-1457.

Research output: Contribution to journalArticle

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