WASP-39b: a highly inflated Saturn-mass planet orbiting a late G-type star

F. Faedi, S. C. C. Barros, D. R. Anderson, D. J. A. Brown, A. Collier Cameron, D. Pollacco, I. Boisse, G. Hébrard, M. Lendl, T. A. Lister, B. Smalley, R. A. Street, A. H. M. J. Triaud, J. Bento, F. Bouchy, O. W. Butters, B. Enoch, C. A. Haswell, C. Hellier, F. P. KeenanG. R. M. Miller, V. Moulds, C. Moutou, A. J. Norton, D. Queloz, A. Santerne, E. K. Simpson, I. Skillen, A. M. S. Smith, S. Udry, C. A. Watson, R. G. West, P. J. Wheatley

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We present the discovery of WASP-39b, a highly inflated transiting Saturn-mass planet orbiting a late G-type dwarf star with a period of 4.055259 +/- 0.000008 d, Transit Epoch T-0 = 2 455 342.9688 +/- 0.0002 (HJD), of duration 0.1168 +/- 0.0008 d. A combined analysis of the WASP photometry, high-precision follow-up transit photometry, and radial velocities yield a planetary mass of M-pl = 0.28 +/- 0.03 M-J and a radius of R-pl = 1.27 +/- 0.04 R-J, resulting in a mean density of 0.14 +/- 0.02 rho(J). The stellar parameters are mass M-star = 0.93 +/- 0.03 M-circle dot, radius R-star = 0.895 +/- 0.23 R-circle dot, and age 9(-4)(+3) Gyr. Only WASP-17b and WASP-31b have lower densities than WASP-39b, although they are slightly more massive and highly irradiated planets. From our spectral analysis, the metallicity of WASP-39 is measured to be [Fe/H] = -0.12 +/- 0.1 dex, and we find the planet to have an equilibrium temperature of 1116(-32)(+33) K. Both values strengthen the observed empirical correlation between these parameters and the planetary radius for the known transiting Saturn-mass planets.
Original languageEnglish
Article numberA40
Pages (from-to)1-8
JournalAstronomy and Astrophysics
Publication statusPublished - Jul 2011

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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