The transit light curve project. IX. Evidence for a smaller radius of the exoplanet XO-3b

Joshua N. Winn, Matthew J. Holman, Guillermo Torres, Peter Mccullough, Christopher Johns-Krull, David W. Latham, Avi Shporer, Tsevi Mazeh, Enrique Garcia-Melendo, Cindy Foote, Gil Esquerdo, Mark Everett

Research output: Contribution to journalArticlepeer-review

243 Scopus citations


We present photometry of 13 transits of XO-3b, a massive transiting planet on an eccentric orbit. Previous data led to two inconsistent estimates of the planetary radius. Our data strongly favor the smaller radius, with increased precision: Rp = 1.217 ± 0.073 RJup. A conflict remains between the mean stellar density determined from the light curve, and the stellar surface gravity determined from the shapes of spectral lines. We argue the light curve should take precedence, and revise the system parameters accordingly. The planetary radius is about 1 a larger than the theoretical radius for a hydrogen-helium planet of the given mass and insolation. To help in planning future observations, we provide refined transit and occultation ephemerides.

Original languageEnglish (US)
Pages (from-to)1076-1084
Number of pages9
JournalAstrophysical Journal
Issue number2
StatePublished - Aug 20 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Planetary systems
  • Stars: individual (GSC 03727-01064, XO-3)


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