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

The ESO Public Survey VISTA Variables in the Via Lactea (VVV) provides deep multi-epoch infrared observations for an unprecedented 562 sq. deg 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 JHK_s 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 Myr) and massive (3 ± 2 × 10³ M_⊙) 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 M_⊙.