K2-31B, A GRAZING TRANSITING HOT JUPITER ON A 1.26-DAY ORBIT AROUND A BRIGHT G7V STAR

We report the discovery of K2-31b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. K2-31b is a 1.8-Jupiter-mass planet on a 1.26-day orbit around a G7 V star (M* =0.91 M⊙, R* =0.78 R ⊙). The planetary radius is poorly constrained (0.7 < Rp < 1.4 RJup), owing to the grazing transit and the low sampling rate of the K2 photometry.