WASP-78b and WASP-79b: Two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus

Abstract

We report the discovery of WASP-78b and WASP-79b, two highly-bloated Jupiter-mass exoplanets orbiting F-type host stars. WASP-78b orbits its V = 12.0 host star (TYC 5889-271-1) every 2.175 days and WASP-79b orbits its V = 10.1 host star (CD-30 1812) every 3.662 days. Planetary parameters have been determined using a simultaneous fit to WASP and TRAPPIST transit photometry and CORALIE radial-velocity measurements. For WASP-78b a planetary mass of 0.89 ± 0.08 M Jup and a radius of 1.70 ± 0.11 R Jup is found. The planetary equilibrium temperature of T P = 2350 ± 80 K for WASP-78b makes it one of the hottest of the currently known exoplanets. WASP-79b its found to have a planetary mass of 0.90 ± 0.08 M Jup, but with a somewhat uncertain radius due to lack of sufficient TRAPPIST photometry. The planetary radius is at least 1.70 ± 0.11 R Jup, but could be as large as 2.09 ± 0.14 R Jup, which would make WASP-79b the largest known exoplanet. © 2012 ESO.