WASP-25b: A 0.6MJ planet in the Southern hemisphere

Abstract

We report the detection of a 0.6MJ extrasolar planet by WASP-South, WASP-25b, transiting its solar-type host star every 3.76 d. A simultaneous analysis of the WASP, FTS and Euler photometry and CORALIE spectroscopy yields a planet of Rp = 1.22RJ and Mp = 0.58MJ around a slightly metal-poor solar-type host star, [Fe/H] = -0.05 ± 0.10, of R* = 0.92R⊙ and M* = 1.00M⊙. WASP-25b is found to have a density of ρp = 0.32 ρJ, a low value for a sub-Jupiter mass planet. We investigate the relationship of planetary radius to planetary equilibrium temperature and host star metallicity for transiting exoplanets with a similar mass to WASP-25b, finding that these two parameters explain the radii of most low-mass planets well. © 2010 The Authors. Journal compilation © 2010 RAS.