This means that there is probably a previously unseen companion star orbiting the star [4]. (alma-telescope.jp)
From the movements of a number of nearby stars we have now detected unseen companion bodies in orbit around them that are about as massive as large planets. (scientificamerican.com)
Most planet hunters watch for wobbles in the light from stars, which arise from the back - and - forth gravitational tugs of unseen companions. (sciencemag.org)