HATS-18 b: An Extreme Short--Period Massive Transiting Planet Spinning Up Its Star
astro-ph.EP
/ Authors
Kaloyan M. Penev, Joel D. Hartman, Gaspar A. Bakos, Simona Ciceri, Rafael Brahm, Daniel Bayliss, Joao Bento, Andr'es Jord'an, Zoltan Csubry, W. Bhatti
and 12 more authors
Miguel de Val-Borro, Néstor Espinoza, George Zhou, Luigi Mancini, Markus Rabus, Vincent Suc, Thomas Henning, Brian P. Schmidt, Robert W. Noyes, J. L'az'ar, Istvan Papp, P. S'ari
/ Abstract
We report the discovery by the HATSouth network of HATS-18 b: a 1.980 +/- 0.077 Mj, 1.337 +0.102 -0.049 Rj planet in a 0.8378 day orbit, around a solar analog star (mass 1.037 +/- 0.047 Msun, and radius 1.020 +0.057 -0.031 Rsun) with V=14.067 +/- 0.040 mag. The high planet mass, combined with its short orbital period, implies strong tidal coupling between the planetary orbit and the star. In fact, given its inferred age, HATS-18 shows evidence of significant tidal spin up, which together with WASP-19 (a very similar system) allows us to constrain the tidal quality factor for Sun-like stars to be in the range 6.5 <= lg(Q*/k_2) <= 7 even after allowing for extremely pessimistic model uncertainties. In addition, the HATS-18 system is among the best systems (and often the best system) for testing a multitude of star--planet interactions, be they gravitational, magnetic or radiative, as well as planet formation and migration theories.