WASP-28b: a hot Jupiter transiting a low-metallicity star

We report the discovery of a transiting exoplanet in a 3.408 day orbit about an early G-type star. The host star has a mass of 1.08 ± 0.04M_sun , a radius of 1.05 ± 0.06R_sun, an effective temperature of 6100 ± 150K, and a metallicity [Fe/H] = −0.29 ± 0.10 which is amongst the lowest measured for the host star of a transiting exoplanet. We combine the available spectral and photometric data to measure the planet’s mass of 0.91 ± 0.06M_J and radius of 1.12 ± 0.06R_J . We find the measured radius to be consistent with theoretical evolutionary models of an irradiated planet with a low heavy element content.