  BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have
undertaken a study of stellar activity and kinematics for this star over the
past few years. Previous results show a high level of stellar activity, with
the presence of prominence-like structures, spots on the surface and strong
flare events, despite the moderate rotational velocity of the star. In
addition, radial velocity variations with a semi-amplitude of up to 1 km/s were
detected. We investigated the nature of these radial velocity variations, in
order to determine whether they are due to stellar activity or the reflex
motion of the star induced by a companion. We have analysed high-resolution
echelle spectra and also two-band photometry was obtained to produce the light
curve and determine the photometric period. Based upon the analysis of the
bisector velocity span, as well as spectroscopic indices of chromospheric
indicators and taking into account the photometric analysis, we report that the
best explanation for the RV variation is the presence of a sub-stellar
companion. The Keplerian fit of the RV data yields a solution for a close-in
massive planet with an orbital period of 7.78 days. The presence of the
close-in massive planet could also be an interpretation for the high level of
stellar activity detected. Since the RV data are not part of a planet search
program, we can consider our results as a serendipitous evidence of a planetary
companion. To date, this is the youngest main sequence star for which a
planetary candidate has been reported.
