WASP-37b: A 1.8 M J Exoplanet Transiting a Metal-poor Star

We report on the discovery of WASP-37b, a transiting hot Jupiter orbiting an m _v = 12.7 G2-type dwarf, with a period of 3.577469 ± 0.000011 d, transit epoch T ₀ = 2455338.6188 ± 0.0006 (HJD; dates throughout the paper are given in Coordinated Universal Time (UTC)), and a transit duration 0.1304^+0.0018 _-0.0017 d. The planetary companion has a mass M _p = 1.80 ± 0.17 M _J and radius R _p = 1.16^+0.07 _-0.06 R _J, yielding a mean density of 1.15^+0.12 _-0.15 ρ_J. From a spectral analysis, we find that the host star has M _sstarf = 0.925 ± 0.120 M _sun, R _sstarf = 1.003 ± 0.053 R _sun, T _eff = 5800 ± 150 K, and [Fe/H] = -0.40 ± 0.12. WASP-37 is therefore one of the lowest metallicity stars to host a transiting planet.