We report the discovery by the HATSouth network of HATS-18b: a 1.980 ± 0.077 MJ, - 1.337-0.049 +0.102 RJ planet in a 0.8378 day orbit, around a solar analog star (mass 1.037 ± 0.047 M⊙ and radius - 1.020-0.031 +0.057 R⊙) 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 of 6.5≲log10(Q∗/k2)≲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.
- planetary systems
- planets and satellites: detection
- planets and satellites: gaseous planets
- stars: individual (HATS-18)
- stars: rotation
- techniques: photometric