A Binary Orbit for the Massive, Evolved Star HDE 326823, a WR+O System Progenitor

TL;DR

This paper presents spectroscopic evidence that HDE 326823 is a close binary system with a hot star losing mass to a hidden companion, contributing to understanding the evolution of massive, nitrogen-enriched Wolf-Rayet stars.

Contribution

It provides the first orbital solution for HDE 326823, revealing a binary system with mass transfer and a circumbinary disk, advancing knowledge of massive star evolution.

Findings

Absorption lines show coherent Doppler shifts with a 6.123-day period.

Emission lines exhibit little or no velocity variation.

HDE 326823 is likely a short-period WR+O binary undergoing mass transfer.

Abstract

The hot star HDE 326823 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 6.123 d period. We present new, high and moderate resolution spectroscopy of HDE 326823, 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. HDE 326823 probably belongs to a class of objects that produce short-period WR+O binaries.