Aims:We detected tertiary components of close binaries from spectroscopy and light curve modelling, investigated the light-travel time effect and the possibility of magnetic activity cycles, measured mass ratios for unstudied systems, and derived absolute parameters. Methods: We carried out new photometric and spectroscopic observations of five

The abundances of iron and oxygen are homogeneously determined in a sample of 523 nearby (d 5500 K and [Fe/H] -0.3, we find no obvious indication of a sudden decrease (i.e., a "knee") in the [O/Fe] vs. [Fe/H] pattern of thick-disk stars that would connect the thick and thin disk trends at a high metallicity. We conclude that Type Ia supernovae (SN

We report the discovery of a periodic modulation in the optical lightcurve of the candidate ultracompact X-ray binary 4U1822-000. Using time-resolved optical photometry taken with the William Herschel Telescope we find evidence for a sinusoidal modulation with a semi-amplitude of 8 per cent and a period of 191min, which is most likely close to the

The results of the determination of magnetic field strength from weak polarimetric signals in solar internetwork regions are contradictory. We investigate the origin of this contradiction with the help of MHD simulations. It is shown that the Stokes V amplitude ratio of the Fe I λλ15652-15648 lines is a good indicator of kG magnetic field

Star clusters are born in a highly compact configuration, typically with radii of less than about 1 pc roughly independently of mass. Since the star formation efficiency is less than 50 per cent by observation and because the residual gas is removed from the embedded cluster, the cluster must expand. In the process of doing so it only retains a

We present an extensive spectroscopic investigation of evolved old- and intermediate-age stellar tracers of the Carina dSph galaxy. We discuss the approach we devised to calibrate the two European Southern Observatory multi-object spectrographs (FLAMES, FORS2). Pros and cons of the two instruments are also mentioned. Finally, we present preliminary