EN ESTA TESIS SE ESTUDIAN LA DEPENDENCIA DE LA RADIACION GRAVITATORIA GENERADA POR SISTEMAS BINARIOS EN LA EXCENTRICIDAD DE LA ORBITA. ESTE OBJETIVO SE HA CONSEGUIDO MEDIANTE EL USO DE ALGUNAS APROXIMACIONES BASTANTE PRECISAS QUE PERMITEN LA OBTENCION DE RESULTADOS ANALITICOS RELATIVAMENTE SENCILLOS. LAS APROXIMACIONES REALIZADAS SON DE DOS TIPOS

From low and high resolution spectroscopic observations of IRAS 10215-5916 we have discovered the presence of nebular emission lines in this G-type supergiant star in the post-AGB stage. From its high resolution spectrum we derived an expansion velocity of 17 km/s for the shell, similar to the values usually observed in planetary and proto

We report on the Lovers of Active Galaxies' (LAG) monitoring of the Seyfert 1 galaxy Markarian 279 from January to June 1990. The source, which was in a very bright state, gradually weakened after the first month of monitoring: the Hα and Hβ flux decreased by 20% and 35% respectively, and the continuum under Hα by 30%. The luminosity-weighted

We present the results of a combined HST/IUE/ground-based spectroscopic monitoring campaign on the Seyfert 1 galaxy NGC 5548 that was undertaken in order to address questions that require both high temporal resolution (one day) and high signal-to-noise ratios. We find (1) that the ultraviolet and optical continuum variations are virtually

Strong light bridges (SLBs) represent an abrupt change in the physical conditions of sunspot umbrae. They divide the umbra into separate units (fragments, umbral cores) and very often show a granular structure. A photometric and spectroscopic study of SLBs, and also of abnormal granulation (AG) in a region of pores, is presented. Slit-jaw images

We have observed the linear polarization of 21 bright grains of the photospheric network close to the disk center. The linear polarization of Fe I 6302.5 A was always lower than 1.9 x 10-3 (referred to continuum intensity). This level of linear polarization implies a very small magnetic field inclination with respect to the vertical, which we