Evidence against the young hot-Jupiter around BD +20 1790

Context. The young active star BD +20 1790 is believed to host a substellar companion, revealed by radial-velocity measurements that detected the reflex motion induced on the parent star. Aims. A complete characterisation of the radial-velocity signal is necessary in order to assess its nature. Methods. We used CORALIE spectrograph to obtain precise (~10 m/s) velocity measurements on this active star, while characterizing the bisector span variations. Particular attention was given to correctly sample both the proposed planetary orbital period, of 7.8 days, and the stellar rotation period, of 2.4 days. Results. A smaller radial-velocity signal (with peak-to-peak variations <500 m/s) than had been reported previously was detected, with different amplitude on two different campaigns. A periodicity similar to the rotational period is found on the data, as well as a clear correlation between radial-velocities and bisector span. This evidence points towards a stellar origin of the radial-velocity variations of the star instead of a barycentric movement of the star, and repudiates the reported detection of a hot-Jupiter.