Coaxing the Eclipsing Binary V367 Cygni out of Its Shell

Abstract

Spectra that cover 0.63–0.69 μm with a spectral resolution ∼17,000 are presented of the W Serpentis system V367 Cygni. Absorption lines of Fe ii and Si ii 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, Hα changes with time over timescales of no more than two orbits. A tentative detection of He i 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″, or 0.09 pc at the distance of the system; V367 Cyg is thus expelling matter into a large volume of the surrounding space.