2012ApJ...749..134H

We report the discovery of HAT-P-17b,c, a multi-planet system with an inner transiting planet in a short-period, eccentric orbit and an outer planet in a 4.4 yr, nearly circular orbit. The inner planet, HAT-P-17b, transits the bright V = 10.54 early K dwarf star GSC 2717-00417, with an orbital period P = 10.338523±0.000009 days, orbital eccentricity e = 0.342±0.006, transit epoch T_c= 2454801.16943±0.00020 (BJD: barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1690±0.0009 days. HAT-P-17b has a mass of 0.534±0.018 M_J and radius of 1.010±0.029 R_J yielding a mean density of 0.64±0.05 g/cm3. This planet has a relatively low equilibrium temperature in the range 780-927 K, making it an attractive target for follow-up spectroscopic studies. The outer planet, HAT-P-17c, has a significantly longer orbital period P ₂= 1610±20 days and a minimum mass m₂ sin i₂= 1.31^+0.18_–0.15 M_J. The orbital inclination of HAT-P-17c is unknown as transits have not been observed and may not be present. The host star has a mass of 0.86 ± 0.04 M_☉, radius of 0.84±0.02 R_☉, effective temperature 5246±80 K, and metallicity [Fe/H] = 0.00±0.08. HAT-P-17 is the second multi-planet system detected from ground-based transit surveys.