Profiles of the Na I D doublet in three bright features (clusters of umbral dots), located in a relatively dark umbra, were analyzed by means of the 'local two-component modeling' to obtain the 'true' continuum intensities and temperatures of the bright features and their dark surroundings (background). The intensities of two central and one

Results are presented from simultaneous UBVRI photopolarimetric observations of eight blazars at the 2.56-m Nordic Optical Telescope during winter 1991. In 3C 66A the highest ever measured polarization, P(U) = 30.5 percent is observed, with small frequency dependence (FDP), P being lower toward longer wavelengths. In AO 0235 + 164, large changes in

Results of an investigation of 23 planetary nebulae whose post-AGB central stars have been previously analyzed using direct spectroscopic non-LTE methods are presented. A comparison of spectroscopic effective temperatures with Zanstra and Stoy temperatures shows that most PN in the present sample are optically thin in the H-Ly continuum. A good

Results of a program of near-IR monitoring of a sample of blazars and miniblazars observed during 1990 and 1991 with the Carlos Sanchez Telescope, in Teide Observatory, Tenerife are presented. All of the objects in the sample show blazar activity during the course of the observations. Several of the objects in the sample have been monitored for

A grid of evolutionary synthesis models for different scenarios (initial mass function slope, metallicity, age, etc.) and computing a set of observables in a wavelength range extending from soft x-rays to radio is reported. The model predictions were compared with observational data for a sample of 13 star forming galaxies of different morphologies

Strong Langmuir turbulence effects are investigated during ionospheric modification experiments performed at the Arecibo Observatory. Indirect evidence of Langmuir wave collapse is obtained through the observation of theoretically predicted 'caviton-type' enhanced plasma wave spectra. A typical spectrum consists of a 'free-mode' peak with a