Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon. I. V2028 Cygni

We present results of nearly six years of spectroscopic observations of the B[e] star V2028 Cyg. The presence of the cold-type absorption lines combined with a hot-type spectrum indicate the binarity of this object. Since B[e] stars are embedded in an extended envelope, the usage of common stellar atmosphere models for the analysis is quite inappropriate. Therefore, we focus on the analysis of the long-term spectral line variations in order to determine the nature of this object. We present the time dependences of the equivalent width and radial velocities of the Hα line, [O i] 6300 Å, Fe ii 6427, 6433, and 6456 Å lines. The bisector variations and line intensities are shown for the Hα line. The radial velocities are also measured for the absorption lines of the K component. No periodic variation is found. The observed data show correlations between the measured quantities, which can be used in future modelling.

Based on data from the Ondřejov 2 m telescope, Czech Republic.Reduced Ondrejov spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A57