Benjamin J. Fulton, University Hawaii Institute for Astronomy
Karen A. Collins, University of Louisville
B. Scott Gaudi, The Ohio State University
Keivan G. Stassun, Vanderbilt University
Joshua Pepper, Vanderbilt University
Thomas G. Beatty, Pennsylvania State University
Robert J. Siverd, Las Cumbres Observatory Global Telescope Network, Inc
Kaloyan Penev, Princeton University
Andrew W. Howard, University Hawaii Institute for Astronomy
Christoph Baranec, University Hawaii Institute for Astronomy
Giorgio Corfini, Società Astronomica Lunae
Jason D. Eastman, Harvard-Smithsonian Center for Astrophysics
Joao Gregorio, Atalaia Group and CROW Observatory
Nicholas M. Law, The University of North Carolina at Chapel Hill
Michael B. Lund, Lehigh University
Thomas E. Oberst, Westminster College, New Wilmington
Matthew T. Penny, The Ohio State University
Reed Riddle, California Institute of Technology
Joseph E. Rodriguez, Lehigh University
Daniel J. Stevens, The Ohio State University
Roberto Zambelli, Società Astronomica Lunae
Carl Ziegler, The University of North Carolina at Chapel Hill
Allyson Bieryla, Harvard-Smithsonian Center for Astrophysics
Giuseppe D'Ago, Istituto Internazionale per gli Alti Studi Scientifici (IIASS)
Darren L. DePoy, Texas A&M University
Eric L.N. Jensen
John F. Kielkopf, University of Louisville
David W. Latham, Harvard-Smithsonian Center for Astrophysics
Mark Manner, Spot Observatory
Jennifer Marshall, Texas A&M University
Kim K. McLeod, Wellesley College
Phillip A. Reed, Kutztown University

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We announce the discovery of a highly inflated transiting hot Jupiter by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with Teff = 5754-55+54 K, log g = 4.078-0.054+0.049, [Fe/H] = 0.272 ± 0.038, an inferred mass M∗ = 1.211 -0.066+0.078 M⊙, and radius R∗ = 1.67-0.12+0.14 R⊙. The planetary companion has a mass MP = 0.867-0.061+0.065 MJ, radius RP = 1.86-0.16+0.18 RJ, surface gravity log gP = 2.793-0.075+0.072, and density ρP = 0.167-0.038+0.047 g cm-3. The planet is on a roughly circular orbit with semimajor axis a = 0.04571-0.00084+0.00096 AU and eccentricity e = 0.035-0.025+0.050. The best-fit linear ephemeris is T0 = 2456883.4803 ± 0.0007 BJDTDB and P = 3.24406 ± 0.00016 days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly irradiated gas giants. The low stellar log g and large implied radius are supported by stellar density constraints from follow-up light curves, as well as an evolutionary and space motion analysis. We also develop a new technique to extract high-precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of Teq = 1675-55+61 K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.

Publication Source (Journal or Book title)

Astrophysical Journal