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Astrophysics

Title: Detection of an Extrasolar Planet Atmosphere

Abstract: We report high precision spectrophotometric observations of four planetary transits of HD 209458, in the region of the sodium resonance doublet at 589.3 nm. We find that the photometric dimming during transit in a bandpass centered on the sodium feature is deeper by (2.32 +/- 0.57) x 10^{-4} relative to simultaneous observations of the transit in adjacent bands. We interpret this additional dimming as absorption from sodium in the planetary atmosphere, as recently predicted from several theoretical modeling efforts. Our model for a cloudless planetary atmosphere with a solar abundance of sodium in atomic form predicts more sodium absorption than we observe. There are several possibilities that may account for this reduced amplitude, including reaction of atomic sodium into molecular gases and/or condensates, photoionization of sodium by the stellar flux, a low primordial abundance of sodium, or the presence of clouds high in the atmosphere.
Comments: 26 pages, 8 figures, accepted by ApJ 2001 November 19
Subjects: Astrophysics (astro-ph)
Journal reference: Astrophys.J.568:377-384,2002
DOI: 10.1086/338770
Cite as: arXiv:astro-ph/0111544
  (or arXiv:astro-ph/0111544v1 for this version)

Submission history

From: David Charbonneau [view email]
[v1] Wed, 28 Nov 2001 21:24:02 GMT (146kb)