SIMBAD references

The results of a search for interstellar and circumstellar absorption lines in high-resolution optical spectra of seven late-type stars are presented. All these stars are single-lined spectroscopic binaries with unseen companions, presumably white dwarfs. Some residual material indicative of recent mass transfer from an asymptotic giant branch (AGB) star might still be associated with the systems. Peculiar energy distribution and the sodium D₁and D₂ lines give direct evidence about the material in the line of sight in some cases. Absorption features of simple carbon-bearing molecules (C₂, CN) have been detected in most of the examined stars, confirming a carbon-rich nature of the corresponding medium. The presence of four well-known prominent diffuse absorption bands at 5780, 5797, 5705, and 5844 Å, belonging to different families, was examined. We have not found clear evidence for these bands in the programme stars. The possible explanations are discussed in brief.