We have observed, with high spectral resolution, the BeII resonance doublet at λ 3131A in five G and K-type main-sequence stars belonging to the Hyades open cluster, as well as in four K-type probable members of the Ursa Major Group. We carried out a detailed abundance analysis via spectral synthesis fitting and studied the utility of the BeII

EK Cep is a double-lined eclipsing binary system with unique characteristics. Accurate absolute dimensions are available, a good determination of the surface lithium abundance has been made, the system is known to show apsidal motion variations, and its secondary component seems to be in the pre main sequence phase. Due to all this, it appears to

Visual and infrared light curves of the noncontact, short period, close binary system UR Tauri were obtained in 1992 November. A new ephemeris of the binary is given using the times of minima inferred from all the observations of the system to date. New light and photometric data from the analysis of the B, V and J,K light curves via the Wilson

We have put into practice the technique to minimize the instrumental polarization (IP) of coude telescopes proposed by Martinez Pillet & Sanchez Almeida (1991): a λ/2-plate inserted into the optical path, with the proper orientation, cancels the IP. The compensation of the Gregory-Coude Telescope at the Observatorio del Teide turns out to fulfil

We have performed two-dimensional spectroscopy of the Seyfert galaxies NGC 5728 and 4151 in the 4500-7500A spectral range. The data (especially the [OIII] lambdalambda4959, 5007 lines), obtained using a new optical fibre system, complement previous observational work carried out by means of this technique. The two gaseous components found in NGC

We solve the line transfer problem in evolving H ii regions in order to calculate line profiles of hydrogen recombination (Hα) and forbidden oxygen ([O III] 5007) lines along several lines of sight during the photo- disruption of molecular cloud cores, or high-density condensation. The density, velocity, and ionization structure of spherically