Radio observations of massive stars in the Galactic centre: The Arches Cluster

TL;DR

This study provides high-resolution radio observations of the Arches cluster, revealing new radio stars, their emission characteristics, and stability, which can help determine the cluster's age and mass.

Contribution

It offers the most detailed radio survey of the Arches cluster to date, nearly doubling known radio stars and analyzing their emission and variability.

Findings

Nine radio stars have thermal emission from stellar winds.

One star is a confirmed colliding wind binary.

Radio emission is stable over several years.

Abstract

We present high-angular-resolution radio observations of the Arches cluster in the Galactic centre, one of the most massive young clusters in the Milky Way. The data were acquired in two epochs and at 6 and 10 GHz with the Karl G. Jansky Very Large Array (JVLA). The rms noise reached is three to four times better than during previous observations and we have almost doubled the number of known radio stars in the cluster. Nine of them have spectral indices consistent with thermal emission from ionised stellar winds, one is a confirmed colliding wind binary (CWB), and two sources are ambiguous cases. Regarding variability, the radio emission appears to be stable on timescales of a few to ten years. Finally, we show that the number of radio stars can be used as a tool for constraining the age and/or mass of a cluster and also its mass function.