Properties of massive stars in four clusters of the VVV survey

TL;DR

This study analyzes massive stars in four newly discovered clusters from the VVV survey to understand their evolution, surface abundances, and mass loss rates, providing new observational constraints on massive star evolution.

Contribution

It presents the first detailed spectroscopic analysis of massive stars in four VVV clusters, revealing evolutionary stages and chemical abundances with radiative transfer modeling.

Findings

Wolf-Rayet stars are more luminous or hotter than O stars.

WN stars are more chemically evolved than O stars, WC stars are more evolved than WN stars.

Mass loss rates in Wolf-Rayet stars are ten times higher than in O stars.

Abstract

The evolution of massive stars is only partly understood. Observational constraints can be obtained from the study of massive stars located in young massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered several new clusters hosting massive stars. We present an analysis of massive stars in four of these new clusters. Our aim is to provide constraints on stellar evolution and to better understand the relation between different types of massive stars. We use the radiative transfer code CMFGEN to analyse K-band spectra of twelve stars with spectral types ranging from O and B to WN and WC. We derive the stellar parameters of all targets as well as surface abundances for a subset of them. In the Hertzsprung-Russell diagram, the Wolf-Rayet stars are more luminous or hotter than the O stars. From the log(C/N) - log(C/He) diagram, we show quantitatively that WN stars are more chemically evolved than O stars, WC stars being more evolved than WN stars. Mass loss rates among Wolf-Rayet stars are a factor of 10 larger than for O stars, in agreement with previous findings.