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

¹ Gemini Observatory, Northern Operations Center, 670 North A’ohoku Place, Hilo, HI 96720, USA
e-mail: andrenicolas.chene@gmail.com
² Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, Valparaíso, Chile
³ Millennium Institute of Astrophysics, MAS, Chile
⁴ LUPM-UMR 5299, CNRS & Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
⁵ Astronomical Institute of the ASCR, Fričova 298, 251 65 Ondřejov, Czech Republic
⁶ Universidade Federal do Rio Grande do Sul, Departamento de Astronomia CP 15051, RS, 91501-970 Porto Alegre, Brazil
⁷ Pontificia Universidad Católica de Chile, Facultad de Física, Departamento de Astronomía y Astrofísica, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago
⁸ Vatican Observatory, V00120 Vatican City State
⁹ Departamento de Ciencias Fisicas, Universidad Andres Bello, Republica 220, Santiago, Chile

Received: 24 February 2015
Accepted: 25 September 2015

Abstract

Context. The ESO Public Survey VISTA Variables in the Vía Láctea (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_⊙.