HATS-6b: A WARM SATURN TRANSITING AN EARLY M DWARF STAR, AND A SET OF EMPIRICAL RELATIONS FOR CHARACTERIZING K AND M DWARF PLANET HOSTS

We report the discovery by the HATSouth survey of HATS-6b, an extrasolar planet transiting a V = 15.2 mag, i = 13.7 mag M1V star with a mass of 0.57 M sub([middot in circle]) and a radius of 0.57 R sub([middot in circle]). HATS-6b has a period of P = 3.3253 d, mass of M sub(p) = 0.32 M sub(J) , radius of R sub(p) = 1.00 R sub(J) , and zero-albedo equilibrium temperature of T sub(eq) = 712.8 + or - 5.1 K. HATS-6 is one of the lowest mass stars known to host a close-in gas giant planet, and its transits are among the deepest of any known transiting planet system. We show that from the transit-based stellar density alone it is possible to measure the mass and radius of a ~0.6 M sub([middot in circle]) star to ~7 and ~2% precision, respectively.