Periodic variability of the T tauri star DI cephei

Original spectroscopic and photometric observations are used together with data from the literature to compile a master light curve for DI Cep and to analyze individual data series for periodicity. The spectroscopic data reveal the period P=9.24^d. Data from different authors show the nine-day quasi-periodicity in the brightness variations fairly reliably, although the period cannot be derived from the entire master set of photometric data. The period P=18.28^d is also derived from the V brightnesses. We find variations of the zero epoch of the nine-day period, possibly due to the changing location of an accretion-disk hot spot.