IRAS 17423-1755 has been recognized as a new bipolar nebula during a multi-wavelength observational program of unidentified IRAS sources with far infrared colours similar to those of known planetary nebulae. B, V, R and Hα CCD images show a clearly marked bipolar structure with a total extension of ~11 arcsec. The spectrum of the core shows strong

We report broad-band imaging observations which reveal a circum-nuclear gas ring in NGC 4151. The ring is delineated by two arc-like features probably resulting from dust extinction of the background stellar continuum. These features are distributed along opposite quadrants of an elliptical ring which has a semi-major axis of length 1.8kpc and is

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