HAT-P-25b: A HOT-JUPITER TRANSITING A MODERATELY FAINT G STAR

We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 +/- 0.000019 days, transit epoch T-c = 2455176.85173 +/- 0.00047 (BJD-barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0.1174 +/- 0.0017 days. The host star has a mass of 1.01 +/- 0.03 M-circle dot, radius of 0.96(-0.04)(+0.05)R(circle dot), effective temperature 5500 +/- 80 K, and metallicity [Fe/H] = +0.31 +/- 0.08. The planetary companion has a mass of 0.567 +/- 0.022 M-J and radius of 1.190(-0.056)(+0.081) R-J yielding a mean density of 0.42 +/- 0.07 g cm(-3).