Over a Century of Ceti Variability Investigation

We present results of a 2014-2018 campaign of radial velocity measurements of delta Ceti. Combining our determination of pulsation period with historical data we conclude that the most likely explanation of observed changes is the presence of a secondary component with a minimum mass of 1.10 +/- 0.05 M-circle dot on an orbit with a period of 169 +/- 6 yr. Consequently, we revised the intrinsic, evolutionary period change rate to be not larger than 0.018 +/- 0.004 s/century, which is significantly lower than previous estimations and is consistent with evolutionary models. We did not find any significant multiperiodic frequencies in radial velocity periodograms such as those reported in the photometric data from the MOST satellite. Using interferometric angular size of delta Ceti from JMMC Stellar Diameters Catalogue we determined several physical parameters of the star with bolometric flux method. They turned out to be consistent with most previous determinations, confirming lower mass and slower evolution of delta Ceti than obtained using different methods.