摘要：We report the discovery of EPIC246851721b, a “tropical” Jupiter in a 6.18-day orbit around the bright (V=11.439) star EPIC 246851721 (TYC 1283-739-1). We present a detailed analysis of the system using K2 and ground-based photometry, radial velocities, Doppler tomography, and adaptive optics imaging. From our global models, we infer that the host star is a rapidly rotating ( v I sin =74.92 - km s 1 ) F dwarf with T eff =6202K, = R R 1.586 and = M M 1.317 . EPIC246851721b has a radius of 1.051±0.044 R J , and a mass of 3.0 - + 1.2 1.1 M J . Doppler tomography reveals an aligned spin–orbit geometry, with a projected obliquity of - - + 1.47 0.86 0.87 , making EPIC 246851721 the fourth hottest star to host a Jovian planet with P>5 days and a known obliquity. Using quasi-periodic signatures in its light curve that appear to be spot modulations, we estimate the star’s rotation period, and thereby infer the true obliquity of the system to be - + 3.7 1.8 3.7 . We argue that this near-zero obliquity is likely to be primordial rather than a result of tidal damping. The host star also has a bound stellar companion, a 0.4 M M dwarf at a projected separation of 2100au, but the companion is likely incapable of emplacing EPIC246851721b in its current orbit via high-eccentricity Kozai-Lidov migration.
关键词：planetary systems;planets and satellites: detection;stars: individual (EPIC 246851721)
