Related papers: The massive binary population of the starburst clu…
Massive stars and their stellar winds are important for a number of feedback processes. The mass lost in the stellar wind can help determine the end-point of the star as a NS or a BH. However, the impact of mass-loss on the post-Main…
We report the discovery of a population of Wolf-Rayet stars in the young Galactic open cluster Westerlund 1. In an incomplete shallow spectroscopic survey, we find six nitrogen-rich (WN) and five carbon-rich (WC) WR stars. We also confirm…
After leaving the main sequence, massive stars undergo complex evolution, still poorly understood. With a population of 100s OB stars, the starburst cluster Westerlund~1 offers an unparallelled environment to study their evolutionary…
The distance of the very young open cluster Westerlund 2, which contains the very massive binary system WR 20a and is likely associated with a TeV source, has been the subject of much debate. We attempt a joint analysis of spectroscopic and…
We examine the level of substructure and mass segregation in the massive, young cluster Westerlund 1. We find that it is relatively smooth, with little or no mass segregation, but with the massive stars in regions of significantly higher…
An unsettled question concerning the formation and distribution of massive stars is whether they must be born in massive clusters and, if found in less dense environments, whether they must have migrated there. With the advent of wide-area…
We report the discovery of a hitherto undetected population of Wolf-Rayet stars in the young galactic open cluster Westerlund 1. Optical spectroscopy of the cluster identified 11 such objects; provisional classification suggests that 6 are…
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…
Mass-loss in massive stars plays a critical role in their evolution, although the precise mechanism(s) responsible - radiatively driven winds, impulsive ejection and/or binary interaction -remain uncertain. In this paper we present ALMA…
Context. Westerlund I is the richest young cluster currently known in our Galaxy, making it one of the most massive clusters for which we can resolve the individual stars even in the crowded centre. This makes it an ideal target to assess…
The Galactic open cluster Westerlund 1 (Wd 1) represents the ideal local template for extragalactic young massive star clusters, because it is currently the only nearby young cluster which reaches a mass of around 10^5 Msun. The proximity…
We present a structural analysis of the young massive star cluster Westerlund 1 (Wd 1). With multi-epoch Hubble Space Telescope (HST) observations, we measure the proper motions of $10346$ stars and determine their kinematic memberships by…
The typically large distances, extinction, and crowding of Galactic supermassive star clusters have so far hampered the identification of their very low mass members, required to extend our understanding of star and planet formation, and…
Aims. The properties of the early-type stars in the core of the Westerlund2 cluster are examined in order to establish a link between the cluster and the very massive Wolf-Rayet binary WR20a as well as the HII complex RCW49. Methods.…
We present new spectroscopic and photometric observations of the young Galactic open cluster Westerlund 1 (Wd 1) that reveal a unique population of massive evolved stars. We identify ~200 cluster members and present spectroscopic…
Results: The two Wolf-Rayet stars WR20a (WN6ha+WN6ha) and WR20b (WN6ha) were analyzed in detail. They are both very luminous and display very hard spectra, but WR20b does not seem to vary. On the contrary, WR20a, a known eclipsing,…
The first soft gamma-ray repeater was discovered over three decades ago, and subsequently identified as a magnetar. However there is currently no consenus on the formation channel(s) of these objects. The presence of a magnetar in the…
We present a suite of binary evolution models with massive primaries (10 $\leq$ M$_1$ $\leq$ 40 M$_\odot$) and periods and mass ratios chosen such that the systems undergo non-conservative mass transfer while the primaries have helium…
High-mass stars are major players in the chemical and dynamical evolution of galaxies, and young massive clusters are the natural laboratories to study their evolution and their impact on star formation processes. Only in recent years have…
We report the detection of 3 additional Wolf-Rayet stars in the young cluster Westerlund 1. They were selected as emission-line star candidates based on 1 micron narrow-band imaging of the cluster carried out at OPD/LNA (Brazil), and then…