Related papers: Distance and age of the massive stellar cluster We…
Only a small number of high mass stars (> 30 Mo) have fundamental parameters (i.e. masses and radii) measured with high enough accuracy from eclipsing binaries to constrain formation and evolutionary models of massive stars. This work aims…
New NTT/SOFI imaging and spectroscopy of the Wolf-Rayet population in Westerlund 1 are presented. Narrow-band near-IR imaging together with follow up spectroscopy reveals four new WR stars, of which three were independently identified…
The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages and other parameters for a variety of clusters in the Solar Neighbourhood. We construct the cluster age distribution, investigate its spatial variations,…
O-type stars are known to significantly contribute to both the dynamics and evolution of galaxies. Massive and luminous, they probably control and regulate the galaxies star formation rates. For this work I performed a redetermination of…
Observational tests of stellar and Galactic chemical evolution call for the joint knowledge of a star's physical parameters, detailed element abundances, and precise age. For cool main-sequence (MS) stars the abundances of many elements can…
We present a new method to determine the age spread of resolved stellar populations in a starburst cluster. The method relies on a two-step process. In the first step, kinematic members of the cluster are identified based on multi-epoch…
We present fundamental parameters of 4 massive eclipsing binaries in the young massive cluster Westerlund 1. The goal is to measure accurate masses and radii of their component stars, which provide much needed constraints for evolutionary…
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…
We present multi-epoch spectroscopic observations of the massive binary system WR21a, which include the January 2011 periastron passage. Our spectra reveal multiple SB2 lines and facilitate an accurate determination of the orbit and the…
Observations of clusters suffer from issues such as completeness, projection effects, resolving individual stars and extinction. As such, how accurate are measurements and conclusions are likely to be? Here, we take cluster simulations…
Young massive stellar clusters are extreme environments and potentially provide the means for efficient particle acceleration. Indeed, they are increasingly considered as being responsible for a significant fraction of cosmic rays (CRs)…
Using ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars in the central 2'x2' of the cluster Westerlund 1 (Wd 1) with a resolution of R~9000 at a central wavelength of 2.30 micron. This allowed us to determine radial…
We have exploited the very precise parallaxes, proper motions and photometry of \textit{Gaia}\, Data Release~2 to study white dwarf members of the Hyades star cluster. Gaia photometry and parallaxes for the eight DA white dwarfs confirmed…
High-dynamic range radio observations of Westerlund 1 are presented that detect a total of 21 stars in the young massive stellar cluster, the richest population of radio emitting stars known for any young massive galactic cluster in the…
A most desirable feature of a standard candle to estimate astronomical distances is robustness against changes in metallicity and age. It is argued that the radii of main sequence stars with spectral types from solar to A0 show predictable…
The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than $\sigma_\pi/\pi\leq0.10$ and…
We searched through a seven-million cubic-parsec volume surrounding each of the four nearest young open clusters with ages from 40 to 80 Myr to identify both the current and past members of the clusters within the Gaia EDR3 dataset. We find…
Context: The Carina Nebula complex (CNC) is one of the most massive and active star-forming regions in our Galaxy and it contains several large young star clusters. The distances of the individual clusters and their physical connection were…
Recent results have suggested that there is tension between the Gaia DR1 TGAS distances and the distances obtained using luminosities determined by eclipsing binaries or asteroseismology on red giant stars. We use the $K_s$-band…
We use several main-sequence models to derive distances (and extinctions), with statistically meaningful uncertainties for 11 star-forming-regions and young clusters. The model dependency is shown to be small, allowing us to adopt the…