Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon

I. V2028 Cygni^⋆,⋆⋆

¹ Faculty of Science, Masaryk University in Brno, Kotlářská 2, 611 37 Brno, Czech Republic
e-mail: jpolster@email.cz
² Astronomical Institute, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8, Czech Republic
e-mail: kor@sirrah.troja.mff.cuni.cz
³ Astronomical Institute of the Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov, Czech Republic

Received: 7 May 2011
Accepted: 27 March 2012

Abstract

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.