The revised physical assumptions incorporated into a previously published evolutionary model for stellar population synthesis in galaxies (Casuso et al., 1989) are outlined. Applying the present version of the model to well defined zones on the nucleus and along a spiral arm of NGC 2903, it is shown that the star-formation rate has increased during

Not Available

We present some preliminary results of a spectroscopic study of the cataclysmic system IR Gem at quiescence during two orbital periods. The spectra covered the wavelength range 4000 7000 Å. The variations with the phase in the equivalent width of the Hα line confirms the existence of a maximum at phase 0.5.

The detection of high late-time luminosity in the type-II plateau supernova 1988A about 500 days after maximum indicates that some mechanism is still providing large amounts of energy to the supernova at this very late phase. We present a review of the observations of this supernova at different phases, and examine the possible mechanisms that can

We present some preliminary results of a time-resolved spectroscopic study of the peculiar cataclysmic system AM CVn. The analysis of He i lines profile variability, suggests the existence of a 1051 s periodicity. This is one of the known photometric periods, candidate to be the orbital period of the system, or the rotational period of the primary.

Visible light curves of the RS CVn short-period system BH Vir, collected over 26 years, have been analyzed.B-V colours indicate that the primary minimum is normally redder than one would expect, assuming the spectroscopic classification of the system components, while the secondary yielded bluer. A qualitative comparison of the different light