The colliding-wind WC9+OB system WR 65 and dust formation by WR stars

TL;DR

This paper investigates the dust formation in the WC9+OB binary system WR 65, revealing a 4.8-year dust emission cycle linked to the colliding-wind binary orbit, with implications for understanding dust production in Wolf-Rayet stars.

Contribution

It provides the first detailed analysis of dust emission variability in WR 65, connecting infrared and X-ray observations to orbital dynamics in colliding-wind Wolf-Rayet binaries.

Findings

Dust emission varies with a 4.8-year period.

Maximum dust emission correlates with maximum star separation.

X-ray and extinction data support an elliptical orbit model.

Abstract

Observations of the WC9+OB system WR 65 in the infrared show variations of its dust emission consistent with a period near 4.8~yr, suggesting formation in a colliding-wind binary (CWB) having an elliptical orbit. If we adopt the IR maximum as zero phase, the times of X-ray maximum count and minimum extinction to the hard component measured by Oskinova & Hamann fall at phases 0.4--0.5, when the separation of the WC9 and OB stars is greatest. We consider WR 65 in the context of other WC8-9+OB stars showing dust emission.