Thursday, February 5, 2015

KELT-7b: A hot Jupiter Around a Fast Rotating F Class Star

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


Bieryla et al


We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of 1.28±0.18 MJ, radius of 1.53+0.046−0.047 RJ, 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, Teff =6789+50−49 K, [Fe/H] =0.139+0.075−0.081, and logg=4.149±0.019. It has a mass of 1.535+0.066−0.054 Msun, a radius of 1.732+0.043−0.045 Rsun, 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 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 most rapidly rotating star to have a reflex signal (and thus mass determination) due to a planetary companion measured.

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