Related papers: A reference framework for extremely metal-poor OB …

Context. The uncertainty in the degree to which radiation-driven winds of hot stars might be affected by small inhomogeneities in the density leads to a corresponding uncertainty in the determination of the atmospheric mass loss rates from…

In the last few years our knowledge of the physics of massive stars has improved tremendously. However, further investigations are still needed, especially regarding accurate calibrations of their fundamental parameters. To this end, we…

Theoretical stellar evolution models are constructed and tailored to the best known, observationally derived characteristics of metal-poor ([Fe/H]$\sim-2.3$) stars representing a range of evolutionary phases: subgiant HD140283, globular…

We report on oxygen abundances determined from medium-resolution near-IR spectroscopy for a sample of 57 carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/ESO survey. The majority of our program stars exhibit oxygen-to-iron…

Extremely metal-poor (XMP) galaxies are chemically, and possibly dynamically, primordial objects in the local Universe. Our objective is to characterize the HI content of the XMP galaxies as a class, using as a reference the list of 140…

We have undertaken quantitative analysis of four LMC and SMC O4--9.7 extreme supergiants using far-ultraviolet FUSE, ultraviolet IUE/HSTand optical VLT UVES spectroscopy. Extended, non-LTE model atmospheres that allow for the consistent…

With the dual aims of enlarging the list of extremely metal-poor stars identified in the Galaxy, and boosting the numbers of moderately metal-deficient stars in directions that sample the rotational properties of the thick disk, we have…

Evolutionary and atmospheric models have become available for young ultralow-mass objects. These models are being used to determine fundamental parameters from observational properties. TiO bands are used to determine effective temperatures…

We present radial velocities, equivalent widths, model atmosphere parameters, and abundances or upper limits for 53 species of 48 elements derived from high resolution optical spectroscopy of 313 metal-poor stars. A majority of these stars…

In this paper we have analyzed 25 Galactic O and early B-stars by means of H and K band spectroscopy, with the primary goal to investigate to what extent a lone near-IR spectroscopy is able to recover stellar and wind parameters derived in…

We present results of a search for extremely metal-poor (EMP) stars in the Large Magellanic Cloud, which can provide crucial information about the properties of the first stars as well as on the formation conditions prevalent during the…

We present and discuss the results of a search for extremely metal-poor stars based on photometry from data release DR1.1 of the SkyMapper imaging survey of the southern sky. In particular, we outline our photometric selection procedures…

(Abridged) Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are…

We have analyzed bibliographical observational data and theoretical predictions, in order to probe the environment in which extremely metal-poor dwarf galaxies (XMPs) reside. We have assessed the HI component and its relation to the optical…

Unevolved metal poor stars are the witness of the early evolution of the Galaxy. The determination of their detailed chemical composition is an important tool to understand the chemical history of our Galaxy. The study of their chemical…

Identification of metal-poor stars among field stars is extremely useful for studying the structure and evolution of the Galaxy and of external galaxies. We search for metal-poor stars using the artificial neural network (ANN) and extend…

The Early Universe, together with many nearby dwarf galaxies, is deficient in heavy elements. The evolution of massive stars in such environments is thought to be affected by rotation. Extreme rotators amongst them tend to form decretion…

Context. Current implementations of mass loss for hot, massive stars in stellar evolution models include a sharp increase in mass loss when blue supergiants become cooler than Teff 20-22kK. This drastic mass-loss jump has been motivated by…

Massive stars play a key role in the evolution of the Universe. Our goal is to compare observed and predicted properties of single Galactic O stars to identify and constrain uncertain physical parameters and processes in stellar evolution…

Context: Determining the parameters of massive stars is crucial to understand many processes in galaxies and the Universe, since these objects are important sources of ionization, chemical enrichment and momentum. 10m class telescopes…