KELT-7b: A hot Jupiter transiting a bright V=8.54 rapidly rotating F-star

Discovery light curve of KELT-7b from the KELT-N telescope. The light curve contains 7745 observations spanning 4.5 years, phase folded to the orbital period of P = 2.7347749 days. The red line represents the same data binned at 1 hr intervals in phase

KELT-7b is a transiting hot Jupiter with a mass of 1.28 ± 0.18 M_J, radius of 1.53 R_J, and an orbital period of 2.7347749 ± 0.0000039 days. The bright host star (HD33643; KELT-7) is an F-star with V=8.54, T_eff =6789 K, [Fe/H] =0.139, and log g = 4.149 ± 0.019. It has a mass of 1.535 M_sun, a radius of 1.732 R_sun, and is the fifth most massive, fifth hottest, and the ninth brightest star known to host a transiting planet. It is also the brightest star around which KELT (Kilodegree Extremely Little Telescope) has discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed characterization given its relatively low surface gravity, high equilibrium temperature, and bright host star. The rapid rotation of the star (73 ± 0.5 km/s) results in a Rossiter-McLaughlin effect with an unusually large amplitude of several hundred m/s. We find that the orbit normal of the planet is likely to be well-aligned with the stellar spin axis, with a projected spin-orbit alignment of λ = 9.7 ± 5.2 degrees. This is currently the second most rapidly rotating star to have a reflex signal (and thus mass determination) due to a planetary companion measured.

Source: arXiv.org