HATS-17b: A TRANSITING COMPACT WARM JUPITER IN A 16.3 DAY CIRCULAR ORBIT*

We report the discovery of HATS-17b, the first transiting warm Jupiter of the HATSouth network. HATS-17b transits its bright ( V = 12.4) G-type ( = , = ) metal-rich ([Fe/H] = +0.3 dex) host star in a circular orbit with a period of P = days. HATS-17b has a very compact radius of given its Jupiter-like mass of . Up to 50% of the mass of HATS-17b may be composed of heavy elements in order to explain its high density with current models of planetary structure. HATS-17b is the longest period transiting planet discovered to date by a ground-based photometric survey, and is one of the brightest transiting warm Jupiter systems known. The brightness of HATS-17 will allow detailed follow-up observations to characterize the orbital geometry of the system and the atmosphere of the planet.