HAT-P-17b,c: A Transiting, Eccentric, Hot Saturn and a Long-period, Cold Jupiter

Abstract

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 cm − 3 . 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 m 2 sin i 2 = 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