* Astronomy

Title: HAT-P-15b: A 10.9-day Extrasolar Planet Transiting a Solar-type Star
Authors: G. Kovács (1), G. Á.Bakos (2,3), J. D. Hartman (2), G. Torres (2), R. W. Noyes (2), D. W. Latham (2), A. W. Howard (4), D. A. Fischer (5), J. A. Johnson (6), G. W. Marcy (4), H. Isaacson (4), D. D. Sasselov (2), R. P. Stefanik (2), G. A. Esquerdo (2), J. M. Fernandez (2,8), B. Béky (2), J. Lázár (7), I. Papp (7), P. Sári (7), ((1) Konkoly Observatory (2) Harvard-Smithsonian Center for Astrophysics (3) NSF Fellow, (4) Department of Astronomy, University of California (5) Department of Astronomy, Yale University (6) California Institute of Technology, Department of Astrophysics (7) Hungarian Astronomical Association (8) Georg-August-Universität Göttingen, Institut für Astrophysik)

We report the discovery of HAT-P-15b, a transiting extrasolar planet in the `period valley', a relatively sparsely-populated period regime of the known extrasolar planets. The host star, GSC 2883-01687, is a G5 dwarf with V=12.16. It has a mass of 1.01±0.04 M(Sun), radius of 1.08±0.04 R(Sun), effective temperature 5568±90 K, and metallicity [Fe/H] = +0.22±0.08. The planetary companion orbits the star with a period 10.863502±0.000027 days, transit epoch Tc = 2454638.56019±0.00048 (BJD), and transit duration 0.2285±0.0015 days. It has a mass of 1.946±0.066 M(Jup), and radius of 1.072±0.043 R(Jup) yielding a mean density of 1.96±0.22 g/cm3. At an age of 6.8±2.1 Gyr, the planet is H/He-dominated and theoretical models require about 2% (10 M(Earth)) worth of heavy elements to reproduce its measured radius. With an estimated equilibrium temperature of 820 K during transit, and 1000 K at occultation, HAT-P-15b is a potential candidate to study moderately cool planetary atmospheres by transmission and occultation spectroscopy.

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