WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit

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Authors

  • M. Lendl
  • D. R. Anderson
  • A. Collier Cameron
  • L. Delrez
  • A. P. Doyle
  • M. Gillon
  • C. Hellier
  • E. Jehin
  • P. F. L. Maxted
  • M. Neveu-VanMalle
  • F. Pepe
  • D. Pollacco
  • D. Queloz
  • D. Ségransan
  • B. Smalley
  • A. M. S. Smith
  • S. Udry
  • V. Van Grootel
  • R. G. West

Colleges, School and Institutes

Abstract

We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of Mp = 0.2755 ± 0.0089 MJ, a radius of  and is in an eccentric (e = 0.302 ± 0.023), 10.02165 ± 0.00055 d orbit around a main-sequence F9 star. The host star's brightness (V = 10.15 mag) makes WASP-117 a good target for follow-up observations, and with a periastron planetary equilibrium temperature of  K and a low planetary mean density () it is one of the best targets for transmission spectroscopy among planets with periods around 10 days. From a measurement of the Rossiter-McLaughlin effect, we infer a projected angle between the planetary orbit and stellar spin axes of β = -44 ± 11 deg, and we further derive an orbital obliquity of   deg. Owing to the large orbital separation, tidal forces causing orbital circularization and realignment of the planetary orbit with the stellar plane are weak, having had little impact on the planetary orbit over the system lifetime. WASP-117b joins a small sample of transiting giant planets with well characterized orbits at periods above ~8 days. 

Details

Original languageEnglish
Article numberA81
Number of pages6
JournalAstronomy and Astrophysics
Volume568
Publication statusPublished - 22 Aug 2014

Keywords

  • planetary systems, techniques: radial velocities, techniques: photometric