Coaxing the Eclipsing Binary V367 Cygni Out of Its Shell

TL;DR

This study presents high-resolution spectra of V367 Cygni, revealing a well-mixed circumsystem shell, a donor star with surface activity, and an extensive dust envelope, providing insights into the system's structure and mass ejection processes.

Contribution

The paper provides detailed spectral analysis of V367 Cygni, including the first extraction of the donor star spectrum and evidence of a large-scale dust environment.

Findings

Shell is smoothly distributed and well-mixed.

Donor star is an early to mid-A giant with surface activity.

V367 Cygni expels matter into a large surrounding volume.

Abstract

Spectra that cover 0.63 - 0.69um with a spectral resolution ~ 17000 are presented of the W Serpentis system V367 Cygni. Absorption lines of FeII and SiII that form in a circumsystem shell are prominent features, and the depths of these are stable with time, suggesting that the shell is smoothly distributed and well-mixed. Further evidence of uniformity comes from modest radial velocity variations measured in the deepest parts of the shell lines. It is suggested that motions previously attributed to rotation of the shell are instead artifacts of contamination from the donor star spectrum. A donor star spectrum is extracted that is consistent with that of an early to mid-A giant. The depths of metallic lines in the donor spectrum vary with orbital phase, suggesting that spot activity covers a large fraction of the surface of that star. A spectrum of the accretion disk that surrounds the second star is also extracted, and similarities are noted with the emission spectra of Herbig Ae/Be stars. In addition to variations with orbital phase, H$\alpha$ changes with time over timescales of no more than two orbits. A tentative detection of HeI 6678 emission is made near primary minimum, but not at other phases. Finally, projected emission from hot dust in and around V367 Cyg is more-or-less symmetric and extends over 28 arcsec, or 0.09 pc at the distance of the system -- V367 Cyg is thus expelling matter into a large volume of the surrounding space.