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

Context. The young active star BD+20 1790 has been inferred to host a substellar companion from radial-velocity measurements that detected the reflex motion induced on the parent star. Aims. We attempt to completely characterize the radial-velocity signal in order to assess its nature. Methods. We used the CORALIE spectrograph to obtain precise (similar to 10 m s(-1)) radial-velocity measurements of this active star, while characterizing the bisector span variations. We took particular care to correctly sample both the proposed planetary orbital period, of 7.8 days, and the stellar rotation period, of 2.4 days. Results. We measure a smaller radial-velocity signal (with peak-to-peak variations <500 m s(-1)) than reported previously, and of different amplitude for two different campaigns. A periodicity similar to the rotational period is found in the data, as well as a clear correlation between radial velocities and bisector span. These results imply that the radial-velocity variations of the star are photospheric in origin and not caused by a barycentric movement movement of the star, and contradict the previous detection of a hot-Jupiter.