HAT-P-13b,c: A Transiting Hot Jupiter with a Massive Outer Companion on an Eccentric Orbit

December 2009 • 2009ApJ...707..446B

Authors • Bakos, G. Á. • Howard, A. W. • Noyes, R. W. • Hartman, J. • Torres, G. • Kovács, Géza • Fischer, D. A. • Latham, D. W. • Johnson, J. A. • Marcy, G. W. • Sasselov, D. D. • Stefanik, R. P. • Sipőcz, B. • Kovács, Gábor • Esquerdo, G. A. • Pál, A. • Lázár, J. • Papp, I. • Sári, P.

Abstract • We report on the discovery of a planetary system with a close-in transiting hot Jupiter on a near circular orbit and a massive outer planet on a highly eccentric orbit. The inner planet, HAT-P-13b, transits the bright V = 10.622 G4 dwarf star GSC 3416 - 00543 every P = 2.916260 ± 0.000010 days, with transit epoch T_c = 2454779.92979 ± 0.00038 (BJD) and duration 0.1345 ± 0.0017 days. The outer planet HAT-P-13c orbits the star every P ₂ = 428.5 ± 3.0 days with a nominal transit center (assuming zero impact parameter) of T _2c = 2454870.4 ± 1.8 (BJD) or time of periastron passage T _2,peri = 2454890.05 ± 0.48 (BJD). Transits of the outer planet have not been observed, and may not be present. The host star has a mass of 1.22^+0.05 _-0.10 M _sun, radius of 1.56 ± 0.08 R _sun, effective temperature of 5653 ± 90 K, and is rather metal-rich with [Fe/H] = +0.41 ± 0.08. The inner planetary companion has a mass of 0.853^+0.029 _-0.046 M _J, and radius of 1.281 ± 0.079 R _J, yielding a mean density of 0.498^+0.103 _-0.069 g cm^-3. The outer companion has m ₂sin i ₂ = 15.2 ± 1.0 M _J, and orbits on a highly eccentric orbit of e ₂ = 0.691 ± 0.018. While we have not detected significant transit timing variations of HAT-P-13b, due to gravitational and light-travel time effects, future observations will constrain the orbital inclination of HAT-P-13c, along with its mutual inclination to HAT-P-13b. The HAT-P-13 (b, c) double-planet system may prove extremely valuable for theoretical studies of the formation and dynamics of planetary systems.

Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO (A146Hr,A264Hr) and NASA (N128Hr,N145Hr).

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