The transit light curve project. XI. Submillimagnitude photometry of two transits of the bloated planet WASP-4b

Joshua N. Winn, Matthew J. Holman, Joshua A. Carter, Guillermo Torres, David J. Osip, Thomas Beatty

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We present photometry of two transits of the giant planet WASP-4b with a photometric precision of 400-800 parts per million and a time sampling of 25-40 s. The two midtransit times are determined to within 6 s. Together with previously published times, the data are consistent with a constant orbital period, giving no compelling evidence for period variations that would be produced by a satellite or additional planets. Analysis of the new photometry, in combination with stellar-evolutionary modeling, gives a planetary mass and radius of 1.237 ± 0.064 MJup and 1.365 ± 0.021 R Jup, respectively. The planet is 15% larger than expected based on previously published models of solar-composition giant planets. With data of the quality presented here, the detection of transits of a "super-Earth" of radius 1.75 R would have been possible.

Original languageEnglish (US)
Pages (from-to)3826-3833
Number of pages8
JournalAstronomical Journal
Issue number4
StatePublished - Apr 1 2009


All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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