Daniel J. Stevens, The Ohio State University
Karen A. Collins, Vanderbilt University
B. Scott Gaudi, The Ohio State University
Thomas G. Beatty, Pennsylvania State University
Robert J. Siverd, Las Cumbres Observatory Global Telescope Network, Inc
Allyson Bieryla, Harvard-Smithsonian Center for Astrophysics
Benjamin J. Fulton, University Hawaii Institute for Astronomy
Justin R. Crepp, University of Notre Dame
Erica J. Gonzales, University of Notre Dame
Carl T. Coker, The Ohio State University
Kaloyan Penev, Princeton University
Keivan G. Stassun, Vanderbilt University
Eric L.N. Jensen, Swarthmore College
Andrew W. Howard, University Hawaii Institute for Astronomy
David W. Latham, Harvard-Smithsonian Center for Astrophysics
Joseph E. Rodriguez, Vanderbilt University
Roberto Zambelli, Società Astronomica Lunae
Valerio Bozza, Università degli Studi di Salerno
Phillip A. Reed, Kutztown University
Joao Gregorio, Crow-Observatory
Lars A. Buchhave, Niels Bohr Institutet
Matthew T. Penny, The Ohio State University
Joshua Pepper, Lehigh University
Perry Berlind, Harvard-Smithsonian Center for Astrophysics
Sebastiano Calchi Novati, Università degli Studi di Salerno
Michael L. Calkins, Harvard-Smithsonian Center for Astrophysics
Giuseppe D'Ago, Vietri sul Mare (SA)
Jason D. Eastman, Harvard-Smithsonian Center for Astrophysics
D. Bayliss, Faculty of Science
Knicole D. Colón, NASA Ames Research Center
Ivan A. Curtis
D. L. DePoy, Texas A&M University
Gilbert A. Esquerdo, Harvard-Smithsonian Center for Astrophysics

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We announce the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting the mildly evolved, V = 10.64 host star TYC 2619-1057-1. We followed up the initial transit signal in the KELT-North survey data with precise ground-based photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the host star has = 6279 ±51 K, = 3.89 ±0.05, [Fe/H] = 0.19+0.08-0.09, = M∗ = 1.59+0.070.09M, and R ∗= 2.37 ±0.17 . The planetary companion has Mp= 0.95 ±0.14 MJ, RP = 1.78+0.17-0.16 RJ, log gP = 2.87+0.9-0.09 and density pp g cm-3, making it one of the most inflated giant planets known. Furthermore, for future follow-up, we report a high-precision time of inferior conjunction in BJDTDB of 2,457,083.660459 ±0.000894 and period of P = 5.0316216 ± 0.000032days. Despite the relatively large separation of ∼0.07 au implied by its ∼5.03-day orbital period, KELT-12b receives significant flux of 2.38+0.32-0.29 × 109 erg s-1 cm-2 from its host. We compare the radii and insolations of transiting gas giant planets around hot (Teff 6250 K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite to search for inflated gas giants in longer-period orbits.

Publication Source (Journal or Book title)

Astronomical Journal