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

TL;DR

This study analyzes six years of spectroscopic data of the B[e] star V2028 Cyg, revealing long-term spectral variations and binarity evidence, with implications for modeling such complex stellar objects.

Contribution

It provides a detailed long-term spectral line variation analysis of V2028 Cyg, highlighting the challenges of modeling B[e] stars embedded in extended envelopes.

Findings

No periodic variation detected in spectral lines.

Correlations found between spectral line measurements.

Spectral variations suggest complex binarity and envelope effects.

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 H alpha line, [O I] 6300 A, Fe II 6427, 6433, and 6456 A lines. The bisector variations and line intensities are shown for the H alpha 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.