The N2 index ([N II] λ6584/Hα) is used to determine emission line galaxy metallicities at all redshifts, including high redshift, where galaxies tend to be metal-poor. The initial aim of this work was to improve the calibrations used to infer oxygen abundance from N2 by employing updated low-metallicity galaxy databases. We compare N2 and the

{ We have studied high-resolution optical spectra of the peculiar B[e] star HD 45677 (FS CMa) observed during 3 nights in October 1995. The main results of our analysis can be summarized as follows: (1) The complex and variable profiles of Hβ indicate the presence of matter outflow. Three blue-shifted absorption components have been detected. (2)

Emission lines in the spectra of WC9 stars have been studied. It is shown that there are clear differences between the spectra of BD + 30 3639 and the central star of He2-99. It is argued that there are no systematic spectral differences between the WC9 CSPN and the Pop.I WC9 stars: both kinds of WC9 stars show a substantial and overlapping range

Context. The young open cluster Dolidze 25, in the direction of the Galactic anticentre, has been attributed a very low metallicity, with typical abundances between -0.5 and -0.7 dex below solar. Aims: We intend to derive accurate cluster parameters and accurate stellar abundances for some of its members. Methods: We have obtained a large sample of

Almost every star in our galaxy will eventually become a white dwarf. Since they are relatively simple compared to main-sequence stars, white dwarfs provide one of the best opportunities for learning about stellar structure and evolution. Studies of pulsating white dwarfs give us the opportunity to learn about their internal composition and

We present a study of high-velocity gas in the direction of 13 halo sub-dwarfs located at absolute value of z approximately equals 0.5-2 kpc and of 8 early-type stars in the Galactic disk at d approximately equals 1-4 kpc. For each line of sight of our sample we collected Ca II and Na I absorption spectra with the 2.5-m Isaac Newton Telescope at La