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

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 G. Jansky Very Large Array. With this work we have quadrupled the number of known radio stars in the cluster. Even though the uncertainty of the measured spectral indices is relatively high, we tentatively classify the 30 detected stars. Eleven have spectral indices consistent with thermal emission from ionised stellar winds, ten have flat to inverted spectral indices indicative of non-thermal emission arising in colliding winds in binaries, and the nine remaining sources cannot be easily classified because of large uncertainties or extremely positive values of the spectral index. The mean mass-loss rate estimated for Wolf-Rayet stars agrees with previous work. Regarding variability, remarkably we find a significantly higher fraction of variable stars in the Quintuplet cluster (∼30%) than in the Arches cluster (< 15%), probably because the Quintuplet cluster is older. 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. © ESO 2022.Karl G. Jansky Very Large Array (JVLA) of the National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation (NSF) operated under cooperative agreement by Associated Universities, Inc. A. T. G.-C., R. S., A. A. and B. S. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). A. T. G.-C., R. S., and B. S. acknowledge financial support from national project PGC2018-095049-B-C21 (MCIU/AEI/FEDER, UE). A. A. acknowledges support from national project PGC2018-098915-B-C21 (MCIU/AEI/FEDER, UE). F. N. acknowledges financial support through Spanish grants ESP2017-86582-C4-1-R and PID2019-105552RB-C41 (MINECO/MCIU/AEI/FEDER) and from the Spanish State Research Agency (AEI) through the Unidad de Excelencia “María de Maeztu”-Centro de Astrobiología (CSIC-INTA) project No. MDM-2017-0737. F. N.-L. gratefully acknowledges funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project-ID 138713538 – SFB 881 (“The Milky Way System”, subproject B8). F.N.-L. acknowledges the sponsorship provided by the Federal Ministry for Education and Research of Germany through the Alexander von Humboldt Foundation. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° [614922].Peer reviewe