We checked the change of the effective temperature with the atmospherical pulsation of rho Cas from combined analyses of optical spectra of 1993-95 and IUE spectra of 1979-81. We find an upper range for bigtriangleup T_eff =~ 750 K over a period of 16-17 months. We present a thorough study of the related absorption line profile changes from which a

The radial scale length of the exponential component of the disc of the Milky Way has been determined in the near infrared. We have used the TMGS (Two Micron Galactic Survey) database which contains positions and K-magnitudes of about 700.000 stars distributed in serveral regions along the galactic plane. From those we have selected areas more than

We describe multi-wavelength, simultaneous observations of the RS CVn star, II Pegasi, most of which were obtained during the first three weeks of September 1992. These observations were made using optical and infra-red broad-band photometry, ultraviolet and optical spectroscopy and microwave monitoring. We have detected photospheric spots and

Palomar 1 is a peculiar Galactic globular cluster suspected of being younger than the bulk of Galactic halo objects. However, such a low age can be confirmed only after a reliable determination of the metallicity. In the present paper, we use the equivalent widths, W, of the Ca II triplet on medium-resolution spectra to determine the metal content

We study the formation of the Li I lambda 6708 Angstroms resonance doublet in spectra of X-ray novae during the stage of outburst decay. We discuss the general conditions on accretion disc parameters which allow the detection of any spectral line absorption component in spectra of self-irradiated accretion discs. We obtain a simple analytical

Esta tesis representa un gran avance en nuestro conocimiento de la influencia del medioambiente en la evolución de las galaxias. El estudio se ha realizado midiendo el Ritmo de Formación Estelar (RFE) de galaxias pertenecientes a Grupos Compactos. Se ha basado endatos astronómicos de buena calidad, obtenidos en los Observatorios del Roque de los