Radio observations of the massive stellar cluster Westerlund 1

TL;DR

This study presents high-dynamic range radio observations of Westerlund 1, revealing 21 radio-emitting stars, including remarkable objects like W9 with high mass-loss, and suggests many WR stars are colliding-wind binaries based on multi-wavelength evidence.

Contribution

First detailed radio survey of Westerlund 1 identifying 21 radio stars, including rare objects and evidence of colliding-wind binaries among WR stars.

Findings

Detection of 21 radio-emitting stars in Westerlund 1

Identification of W9 with high mass-loss rate

Evidence supporting colliding-wind binary nature of WR stars

Abstract

High-dynamic range radio observations of Westerlund 1 are presented that detect a total of 21 stars in the young massive stellar cluster, the richest population of radio emitting stars known for any young massive galactic cluster in the Galaxy. We will discuss some of the more remarkable objects, including the highly radio luminous supergiant B[e] star W9, with an estimated mass-loss rate ~10^{-3} solarmass/yr, comparable to that of eta Carina, along with the somewhat unusual detection of thermal emission from almost all the cool red supergiants and yellow hypergiants. There is strong supporting evidence from X-ray observations that each of the WR stars with radio emission are likely to be colliding-wind binaries