HAT-P-13b,c: A TRANSITING HOT JUPITER WITH A MASSIVE OUTER COMPANION ON AN ECCENTRIC ORBIT

Abstract

We report on the discovery of a planetary system with a close-in transiting\nhot Jupiter on a near circular orbit and a massive outer planet on a highly\neccentric orbit. The inner planet, HAT-P-13b, transits the bright V=10.622 G4\ndwarf star GSC 3416-00543 every P = 2.916260 \\pm 0.000010 days, with transit\nepoch Tc = 2454779.92979 \\pm 0.00038 (BJD) and duration 0.1345 \\pm 0.0017 d.\nThe outer planet, HAT-P-13c orbits the star with P2 = 428.5 \\pm 3.0 days and\nnominal transit center (assuming zero impact parameter) of T2c = 2454870.4 \\pm\n1.8 (BJD) or time of periastron passage T2,peri= 2454890.05 \\pm 0.48 (BJD).\nTransits of the outer planet have not been observed, and may not be present.\nThe host star has a mass of 1.22 \\pm ^0.05_0.10 Msun, radius of 1.56 \\pm 0.08\nRsun, effective temperature 5653 \\pm 90 K, and is rather metal rich with [Fe=H]\n= +0.41 \\pm 0.08. The inner planetary companion has a mass of 0.853\\pm\n^0.029_-0.046MJup, and radius of 1.281 \\pm 0.079 RJup yielding a mean density\nof 0.498\\pm +0.103_-0.069 gcm^-3. The outer companion has m2 sini2 = 15.2 \\pm\n1.0 MJup, and orbits on a highly eccentric orbit of e2 = 0.691 \\pm 0.018. While\nwe have not detected significant transit timing variations of HAT-P-13b, due to\ngravitational and light-travel time effects, future observations will constrain\nthe orbital inclination of HAT-P-13c, along with its mutual inclination to\nHAT-P-13b. The HAT-P-13 (b,c) double-planet system may prove extremely valuable\nfor theoretical studies of the formation and dynamics of planetary systems.\n