A binary orbit for the massive, evolved star HDE 326823, A WR+O system progenitor

Abstract

The hot star HDE326823 is a candidate transition-phase object that is evolving into a nitrogen-enriched Wolf-Rayet star. It is also a known low-amplitude, photometric variable with a 6 day period. We present new, high- and moderate-resolution spectroscopy of HDE326823, and we show that the absorption lines show coherent Doppler shifts with this period while the emission lines display little or no velocity variation. We interpret the absorption line shifts as the orbital motion of the apparently brighter star in a close, interacting binary. We argue that this star is losing mass to a mass gainer star hidden in a thick accretion torus and to a circumbinary disk that is the source of the emission lines. HDE326823 probably belongs to a class of objects that produce short-period WR+O binaries. © 2011. The American Astronomical Society. All rights reserved.