We present a determination of the average space density and birth rate of hydrogen-line (DA) white dwarfs within a radius of 1 kpc around the Sun, based on an observational sample of 360 candidate white dwarfs with g < 19.5 and (g - r) < 0.4, selected from the UV-Excess (UVEX) survey of the northern Galactic plane, in combination with a theoretical

We present a chemical abundance analysis based on high resolution UVES spectra of seventeen bright giant stars in the Globular Cluster (GC) M 22. We obtained an average iron abundance of [Fe/H] = -1.76±0.02 (internal errors only) and an α enhancement of 0.36±0.04 (internal errors only). Na and O, and Al and O follow the well known anticorrelations

We present the results of a high spectral resolution (lambda / Delta lambda = 49 000) study of the circumstellar (CS) gas around the intermediate mass, pre-main sequence star UX Ori. The results are based on a set of 10 échelle spectra covering the spectral range 3800-5900 Å, monitoring the star on time scales of months, days and hours. A large

In many radiative transfer (RT) problems, the sources contain a scattering term that couples all the specific RT equations, one for each frequency and direction, so that solving the problem means solving the system formed by these equations. Each of them is a first-order linear differential equation with its own initial condition assigned at a

Context. Star formation rate (SFR), metallicity, and stellar mass are among the most important parameters of star-forming (SF) galaxies characterizing their formation and evolution. They are known to be related to each other both at low and high redshift in the mass-metallicity, mass-SFR, and metallicity-SFR relations. Aims: We demonstrate the

A detailed study of the brightness, size, spatial distribution, and filling factor of the different umbral inhomogeneities is presented. Many sunspots show multiple umbrae (separated by strong light bridges, SLBs), which behave like independent units. These are termed umbral cores (UCs). From the phenomenological point of view, UCs show two