We report the discovery of KELT-20b, a hot Jupiter transiting a early A star, HD 185603, with an orbital period of days. Archival and follow-up photometry, Gaia parallax, radial velocities, Doppler tomography, and AO imaging were used to confirm the planetary nature of KELT-20b and characterize the system. From global modeling we infer that KELT-20 is a rapidly rotating ( ) A2V star with an effective temperature of K, mass of , radius of , surface gravity of , and age of . The planetary companion has a radius of , a semimajor axis of au, and a linear ephemeris of . We place a upper limit of on the mass of the planet. Doppler tomographic measurements indicate that the planetary orbit normal is well aligned with the projected spin axis of the star ( ). The inclination of the star is constrained to , implying a three-dimensional spin–orbit alignment of . KELT-20b receives an insolation flux of , implying an equilibrium temperature of of ∼2250 K, assuming zero albedo and complete heat redistribution. Due to the high stellar , KELT-20b also receives an ultraviolet (wavelength nm) insolation flux of , possibly indicating significant atmospheric ablation. Together with WASP-33, Kepler-13 A, HAT-P-57, KELT-17, and KELT-9, KELT-20 is the sixth A star host of a transiting giant planet, and the third-brightest host (in V ) of a transiting planet.
M. B. Lund, J. E. Rodriguez, G. Zhou, B. S. Gaudi, K. G. Stassun, M. C. Johnson, A. Bieryla, R. J. Oelkers, D. J. Stevens, K. A. Collins, K. Penev, S. N. Quinn, D. W. Latham, S. Villanueva Jr., J. D. Eastman, J. F. Kielkopf, T. E. Oberst, Eric L.N. Jensen, David H. Cohen, M. D. Joner, D. C. Stephens, H. Relles, G. Corfini, J. Gregorio, R. Zambelli, G. A. Esquerdo, M. L. Calkins, P. Berlind, D. R. Ciardi, C. Dressing, R. Patel, P. Gagnon, E. Gonzales, T. G. Beatty, R. J. Siverd, J. Labadie-Bartz, R. B. Kuhn, K. D. Colón, D. James, J. Pepper, B. J. Fulton, K. K. McLeod, C. Stockdale, S. Calchi Novati, D. L. DePoy, A. Gould, J. L. Marshall, M. Trueblood, P. Trueblood, J. A. Johnson, J. Wright, N. McCrady, R. A. Wittenmyer, S. A. Johnson, A. Sergi, M. Wilson, and D. H. Sliski.
"KELT-20b: A Giant Planet With A Period Of P ~ 3.5 Days Transiting The V ~ 7.6 Early A Star HD 185603".