KELT-2Ab: A Hot Jupiter Transiting the Bright (V = 8.77) Primary Star of a Binary System

September 2012 • 2012ApJ...756L..39B

Authors • Beatty, Thomas G. • Pepper, Joshua • Siverd, Robert J. • Eastman, Jason D. • Bieryla, Allyson • Latham, David W. • Buchhave, Lars A. • Jensen, Eric L. N. • Manner, Mark • Stassun, Keivan G. • Gaudi, B. Scott • Berlind, Perry • Calkins, Michael L. • Collins, Karen • DePoy, Darren L. • Esquerdo, Gilbert A. • Fulton, Benjamin J. • Fűrész, Gábor • Geary, John C. • Gould, Andrew • Hebb, Leslie • Kielkopf, John F. • Marshall, Jennifer L. • Pogge, Richard • Stanek, K. Z. • Stefanik, Robert P. • Street, Rachel • Szentgyorgyi, Andrew H. • Trueblood, Mark • Trueblood, Patricia • Stutz, Amelia M.

Abstract • We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V = 8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived "blue-hook" stage of evolution, with T _eff = 6148 ± 48 K, log g = 4.030^+0.015 _{- 0.026} and [Fe/H] = 0.034 ± 0.78. The inferred stellar mass is M _* = 1.314^+0.063 _{- 0.060} M _⊙ and the star has a relatively large radius of R _* = 1.836^+0.066 _{- 0.046} R _⊙. The planet is a typical hot Jupiter with period 4.1137913 ± 0.00001 days and a mass of M_P = 1.524 ± 0.088 M _J and radius of R_P = 1.290^+0.064 _{- 0.050} R _J. This is mildly inflated as compared to models of irradiated giant planets at the ~4 Gyr age of the system. KELT-2A is the third brightest star with a transiting planet identified by ground-based transit surveys, and the ninth brightest star overall with a transiting planet. KELT-2Ab's mass and radius are unique among the subset of planets with V < 9 host stars, and therefore increases the diversity of bright benchmark systems. We also measure the relative motion of KELT-2A and -2B over a baseline of 38 years, robustly demonstrating for the first time that the stars are bound. This allows us to infer that KELT-2B is an early K dwarf. We hypothesize that through the eccentric Kozai mechanism KELT-2B may have emplaced KELT-2Ab in its current orbit. This scenario is potentially testable with Rossiter-McLaughlin measurements, which should have an amplitude of ~44 m s^-1.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2012ApJ...756L..39B
• PDF https://stacks.iop.org/2041-8205/756/L39/pdf
• PREPRINT http://arxiv.org/abs/1206.1592
• DATA http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?type=REFERENCE&bibcode=2012ApJ...756L..39B
• DATA https://irsa.ipac.caltech.edu/bibdata/2012/B/2012ApJ...756L..39B.html
• ELECTR https://doi.org/10.1088%2F2041-8205%2F756%2F2%2FL39
• SPIRES http://inspirehep.net/search?p=find+eprint+arXiv:1206.1592