We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of 1.28 ± 0.18MJ, radius of 1.533 0.0470.046RJ, and an orbital period of 2.7347749 ± 0.0000039 days. The bright host star (HD 33643; KELT-7) is an F-star with V = 8.54, Teff= 6789 4950 K, [Fe/H] 0.139 0.081 = -0.075, and log g = 4.149 ± 0.019. It has a mass of 1.535 0.0540.066 Me, a radius of 1.732 0.0450.043 Re, 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 Kilodegree Extremely Little Telescope (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-1) results in a RossiterMcLaughlin effect with an unusually large amplitude of several hundred m s-1. 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 = 9.7 ± 5. 2. This is currently the second most rapidly rotating star to have a reflex signal (and thus mass determination) due to a planetary companion measured.
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Bieryla, A., Collins, K., Beatty, T., Eastman, J., Siverd, R., Pepper, J., Gaudi, B., Stassun, K., Cañas, C., Latham, D., Buchhave, L., Sanchis-Ojeda, R., Winn, J., Jensen, E., Kielkopf, J., McLeod, K., Gregorio, J., Colón, K., Street, R., Ross, R., Penny, M., Mellon, S., Oberst, T., Fulton, B., Wang, J., Berlind, P., Calkins, M., Esquerdo, G., Depoy, D., Gould, A., Marshall, J., Pogge, R., & Trueblood, M. (2015). KELT-7b: A HOT JUPITER TRANSITING A BRIGHT v = 8.54 RAPIDLY ROTATING F-STAR. Astronomical Journal, 150 (1) https://doi.org/10.1088/0004-6256/150/1/12