A search for Hα absorption in the exosphere of the transiting extrasolar planet HD 209458b

Joshua N. Winn, Yasushi Suto, Edwin L. Turner, Norio Narita, Brenda L. Frye, Wako Aoki, Bun'ei Sato, Toru Yamada

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

There is evidence that the transiting planet HD 209458h has a large exosphere of neutral hydrogen, based on a 15% decrement in Lyman-α flux that was observed by Vidal-Madjar et al. during transits. Here we report upper limits on Hα absorption by the exosphere. The results are based on optical spectra of the parent star obtained with the Subaru High Dispersion Spectrograph. Comparison of the spectra taken inside and outside of transit reveals no exospheric Hα signal greater than 0.1% within a 5.1 Å band (chosen to have the same Δλ/λ as the 15% Lyα absorption). The corresponding limit on the column density of n = 2 neutral hydrogen is N2 ≲ 109cm-2. This limit constrains proposed models involving a hot (∼ 104K) and hydrodynamically escaping exosphere.

Original languageEnglish (US)
Pages (from-to)655-662
Number of pages8
JournalPublications of the Astronomical Society of Japan
Volume56
Issue number4
DOIs
StatePublished - Jan 1 2004

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Planetary systems: individual (HD 209458b)
  • Techniques: spectroscopic

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