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

Radial velocity studies of X-ray binaries still provide the most solid evidence for the existence of stellar-mass black holes. We currently have 20 confirmed cases, with dynamical masses in excess of 3 M[sun]. Accurate masses have been obtained for a subset of systems which give us a hint on the mass spectrum of the black hole population. These

Context: Interpretation of linearly polarized parameters of the lines of complex atoms for the second solar spectrum needs a lot of collisional coefficients which are often poorly known. Aims: We provide general and simple formulae giving the coefficients of the atomic master equation (depolarization, polarization transfer, population transfer, and