Westerlund 1 as a Template for Massive Star Evolution

TL;DR

Westerlund 1, as the most massive young cluster in the Galaxy, serves as an ideal environment to study massive star evolution, supported by new spectral classification and star population analysis.

Contribution

Developed a spectral classification scheme for supergiants in Westerlund 1, enabling identification of over 30 luminous supergiants and expanding the known massive star population.

Findings

Identification of >30 luminous supergiants in Westerlund 1

Presence of approximately 100 less evolved massive stars

Preliminary evidence of stars evolving to the red HR diagram at constant luminosity

Abstract

With a dynamical mass M_dyn ~ 1.3x10e5 M_sun and a lower limit M_cl>5x10e4 M_sun from star counts, Westerlund 1 is the most massive young open cluster known in the Galaxy and thus the perfect laboratory to study massive star evolution. We have developed a comprehensive spectral classification scheme for supergiants based on features in the 6000-9000A range, which allows us to identify >30 very luminous supergiants in Westerlund 1 and ~100 other less evolved massive stars, which join the large population of Wolf-Rayet stars already known. Though detailed studies of these stars are still pending, preliminary rough estimates suggest that the stars we see are evolving to the red part of the HR diagram at approximately constant luminosity.