Massive open star clusters using the VVV survey IV. WR 62-2, a new very massive star in the core of the VVV CL041 cluster

TL;DR

This study confirms VVV CL041 as a young, massive star cluster containing a very massive star candidate, WR 62-2, using deep infrared observations and spectroscopy to determine its fundamental parameters.

Contribution

First detailed analysis of VVV CL041 confirming its mass, age, and the presence of a very massive star candidate using infrared data and spectroscopy.

Findings

VVV CL041 is less than 4 million years old.

The cluster has a mass of approximately 3,000 solar masses.

The most luminous star is a candidate with an initial mass over 100 solar masses.

Abstract

Context The ESO Public Survey VISTA Variables in the V\'ia L\'actea (VVV) provides deep multi-epoch infrared observations for an unprecedented 562 sq. degrees of the Galactic bulge and adjacent regions of the disk. Nearly 150 new open clusters and cluster candidates have been discovered in this survey. Aims We present the fourth article in a series of papers focussed on young and massive clusters discovered in the VVV survey. This article is dedicated to the cluster VVV CL041, which contains a new very massive star candidate, WR 62-2. Methods Following the methodology presented in the first paper of the series, wide-field, deep JHKs VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters (distance, reddening, mass, age) of VVV CL041. Results We confirm that the cluster VVV CL041 is a young (less than 4 Myrs) and massive (3 +/- 2 x 10^3 Msol) cluster, and not a simple asterism. It is located at a distance of 4.2 +/- 0.9 kpc, and its reddening is A_V = 8.0 +/- 0.2 mag, which is slightly lower than the average for the young clusters towards the centre of the Galaxy. Spectral analysis shows that the most luminous star of the cluster, of the WN8h spectral type, is a candidate to have an initial mass larger than 100 Msol.