Radio observations of massive stars in the Galactic centre: The Quintuplet cluster

TL;DR

This study uses high-resolution radio observations to identify and analyze massive stars in the Quintuplet cluster, revealing new radio stars, their emission types, variability, and implications for cluster age and mass function.

Contribution

It significantly increases the known radio star population in the Quintuplet cluster and demonstrates the use of radio luminosity functions to constrain cluster properties.

Findings

Quadrupled the number of known radio stars in the cluster.

Found a higher fraction of variable stars compared to the Arches cluster.

Stellar wind mass-loss rates agree with theoretical models.

Abstract

We present high-angular-resolution radio continuum observations of the Quintuplet cluster, one of the most emblematic massive clusters in the Galactic centre. Data were acquired in two epochs and at 6 and 10 GHz with the Karl J. Jansky Very Large Array. With this work, we have quadrupled the number of known radio stars in the cluster. Nineteen of them have spectral indices consistent with thermal emission from ionised stellar winds, five are consistent with colliding wind binaries, two are ambiguous cases, and one was only detected in a single band. Regarding variability, remarkably we find a significantly higher fraction of variable stars in the Quintuplet cluster (approximately 30%) than in the Arches cluster (< 15%), probably due to the older age of the Quintuplet cluster. Our determined stellar wind mass-loss rates are in good agreement with theoretical models. Finally, we show that the radio luminosity function can be used as a tool to constrain the age and the mass function of a cluster.