From H-alpha CCD observations taken with the 4.2-m William Herschel Telescope, a catalog of 456 H II regions of the inner zone of the spiral galaxy NGC 4321 has been compiled. The radial distribution, the distribution of diameters, and the luminosity function for the arm and the interarm H II regions are presented, together with the spatial

Results are presented on an analysis of rapid photometric data of the F2 V star HD 155543, obtained simultaneously from the Observatorio del Teide (Spain) and the Observatorio de San Pedro Martir (Mexico) during May-June, 1987. Strong evidence was found of the presence in this star of acoustic p-mode spectrum; when performing a squared amplitude of

The expected mass loss rates from horizontal branch (HB) and red giant branch models are investigated. The expected dependence of those rates on luminosity, metallicity, helium content, giant mass, and HB morphology is discussed. For an HB distribution depending on metallicity, the values found for the fitting factors in the Reimers

The BBKS (Bardeen, Bond, Kaiser and Szalay) expression for the number density of maxima above a threshold in a random Gaussian field (RGF) is used to develop a mathematical technique that would allow the computation of the probability density of filamentary structures arising at random in such a field. A description is given of a procedure for the

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A set of parameters to characterize azimuthal profiles of galaxies is proposed and applied to the spiral structure of the galaxies NGC 1832 and NGC 7479 observed in the B and I passbands. Interpretations of the observations in terms of the two most widely discussed theories of star formation, the spiral density wave theory and that of self