En esta tesis la población estelar de las galaxias enanas del Grupo Local NGC 185 y Phoenix es investigada a partir de fotometría obtenida en telescopios en tierra y usando diagramas color-magnitud sintéticos. El principal resultado de esta tesis es que ambas galaxias presentan periodos largos de actividad de formación estelar y gradientes en sus

We present spectra for 12 new ultracool dwarfs found in the DENIS infrared survey. Seven of them have spectral types at the bottom of the M-class (M8-M9.5), and the other five belong to the cooler ``L'' class. We also present spectra for the two new L dwarfs found by the EROS 2 proper-motion survey. We introduce a scheme for L dwarf classification

IAUC 7307 available at Central Bureau for Astronomical Telegrams.

We present Johnson B CCD photometry for the whole sample of galaxies of the Universidad Complutense de Madrid (UCM) Survey Lists I and II (Cat. and ). They constitute a well-defined and complete sample of galaxies in the Local Universe with active star formation. The data refer to 191 S0 to Irr galaxies at an averaged redshift of 0.027, and

Helioseismic instruments aboard SOHO are making possible a more accurate way of investigating the internal structure of the Sun. Making use of the different techniques and characteristics of these instruments, it is possible to measure solar oscillations as variations of the photospheric velocity (GOLF, MDI) or as irradiance and radiance

We present a parallax measurement for the very cool degenerate WD 0346+246, the serendipitous discovery of which was reported by Hambly et al. We find an absolute parallax of 36+/-5mas, yielding a distance estimate of 28+/-4pc. The resulting absolute visual magnitude of the object is MV=16.8+/-0.3, making it the second-lowest luminosity white dwarf