A multi-frequency, multi-epoch radio continuum study of the Quintuplet cluster with the Very Large Array

¹ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
² School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
³ Centro de Astrobiología, CSIC-INTA, Ctra de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
⁴ Universitat de València. Departament d'Astronomia i Astrofísica, Facultat de Física, Av. Doctor Moliner 50, Burjassot, Valencia, Spain

^★ Corresponding author: mcano@iaa.es

Received: 14 March 2025
Accepted: 9 July 2025

Abstract

Context. The Quintuplet cluster, located in the Galactic Centre, is one of the few young massive clusters in the Milky Way. It allows us to study dozens of massive, post main-sequence stars individually, providing unique insights into the properties of the most massive stars.

Aims. Our goal is to study the radio continuum emission of the most massive stars in the cluster.

Methods. We carried out a total of nine observations (three in the C-band and six in the X-band) of the Quintuplet cluster with the Karl G. Jansky Very Large Array in the A-configuration. We cross-matched the detected sources with infrared stellar catalogues to ensure cluster membership, calculated their spectral indices, quantified variability, and inferred clumping-scaled mass-loss rates.

Results. We present the most complete catalogue of radio stars in the Quintuplet cluster to date, with a total of 41 detections, and the deepest images of the cluster in the 4–12 GHz range (reaching an rms noise level of 2.3 µJy/beam in the X-band). The six year baseline of our observations allowed us to perform a robust variability assessment, finding that around 60% of the Quintuplet radio stars are variable on timescales of months to years. We derived the spectral indices of 28 out of the 41 sources. Based on their spectral indices and variability, we classified 11 of them as colliding-wind binaries, seven as strictly thermal sources, and ten as ambiguous. Including the ambiguous sources, we estimate a multiplicity fraction of (75 ± 22%). We also computed upper limits for the mass-loss rates of the thermal radio stars, finding them in agreement with typical values for Wolf-Rayet (WNh and WC) stars. Finally, we compared these results to the ones obtained from our analogous study of the Arches cluster.