We present high- and intermediate-resolution spectroscopy of the X-ray nova Centaurus X-4 during its quiescent phase. Our analysis of the absorption features supports a K3-K5 V spectral classification for the companion star, which contributes ~=75 per cent of the total flux at Hα. Using the high-resolution spectra we have measured the rotational

Quantitative structural analysis of the galaxies present in the Hawaiian Deep Fields SSA13 and SSA22 is reported. The structural parameters of the galaxies have been obtained automatically by fitting a two-component model (Sérsic r1/n bulge and exponential disc) to the surface brightness of the galaxies. The galaxies were classified on the basis of

Photometry of a large field around the young globular cluster Palomar 12 has revealed the main sequence of a low surface brightness stellar system. This main sequence is indicative of a stellar population that varies significantly in metallicity and/or age but in the mean is more metal-poor than Pal 12. Under different assumptions for the

We examine the isotope production in star forming regions through a model of stellar-group population synthesis evolution. From this we obtain the light-curves of γ-ray line emission due to radioactive decay of 26Al, 60Fe and the e -e + annihilation line. We discuss in particular, the effects of the dispersion due to the discreteness of the stellar

We have used the optical lines of N II and Fe III to study the wind of the luminous blue variable P Cyg. This was performed by applying a version of the Self Absorption Curve (SAC) method, involving few assumptions, to lines whose flux can be measured. A rather surprising result was obtained; the lines of more excited multiplets without blue

Esta tesis presenta el desarrollo y aplicación de métodos de transporte radiactivo para la investigación de Campos magnéticos en astrofísica mediante el efecto Hanle, con particular interés en los campos Magnéticos débiles de la atmósfera solar (desde 1 mililgauss hasta 11 gauss aproximadamente). En este Rango de intensidades de campo magnético es