WASP-5b: a dense, very hot Jupiter transiting a 12th-mag Southern-hemisphere star

We report the discovery of WASP-5b, a Jupiter-mass planet orbiting a 12th-mag G-type star in the Southern hemisphere. The 1.6-d orbital period places WASP-5b in the class of very hot Jupiters and leads to a predicted equilibrium temperature of 1750 K. WASP-5b is the densest of any known Jovian-mass planet, being a factor of 7 denser than TrES-4, which is subject to similar stellar insolation, and a factor of 3 denser than WASP-4b, which has a similar orbital period. We present transit photometry and radial velocity measurements of WASP-5 (= USNO-B1 0487-0799749), from which we derive the mass, radius and density of the planet: M_P= 1.58^(+0.13)_(−0.08) M_J, R_P= 1.090^(+0.094)_(−0.058) R_J and ρ_P= 1.22^(+0.19)_(−0.24) ρ_J. The orbital period is P= 1.6284296^(+0.0000048)_(−0.0000037) d and the mid-transit epoch is T_C (HJD) = 245 4375.62466^(+0.00026)_(−0.00025)