An analysis has been carried out of the center-to-limb variation of the apparent sizes of the umbra, penumbra, and whole spot. It has revealed that the umbral size decreases with height. This result is interpreted in terms of the penumbral geometrical height scale. A value of 230 km, which is larger than that of the photosphere or the umbra

BVJK light curves of CG Cygni show an apparent infrared excess 0.2 mag out of eclipse, assuming the spectral types of the components to be G9.5V + K3V. The depths of the eclipses also show an excess equal (within the errors) to that at quadrature. The source of these excesses is most probably a circum-system shell of cool material; it cannot be

As the triangular libration points in the Earth-Moon system are of potential interest for optical interferometry, their dynamical property was analyzed adopting realistic models. Quasi-periodic orbits were identified, and their stability investigated. Results show that relative motion leads to baseline variation of 1 to 20 cm/sec, which may be

It is shown that recentering, selecting, and adding up sharp short-exposure images obtained with a photon-counting detector working in time-resolved mode can yield a gain in angular resolution better than a factor of 2. A cross-correlation selection algorithm, appropriate for faint and extended objects, is developed and compared with other image

The authors report the results of high resolution and high S/N observations of diffuse interstellar bands (DIBs) towards SN 1987A in the LMC. For the first time they clearly detect the LMC component of the 5780, 5797 and 6284 Å DIBs, and possibly that of 5778 and 6269 Å. Moreover, they observe the Galactic components of the 5778, 5780, 5797, 6283

EN ESTE TRABAJO SE HA REALIZADO UN ESTUDIO DE LAS PROPIEDADES FISICAS DE UN CONJUNTO EN REGIONES DE HII GIGANTES DE LA GALAXIA M33. LA CALIDAD DE LAS OBSERVACIONES JUNTO CON LA INFORMACION ESPACIAL NOS HA PERMITIDO REALIZAR UN EXAMEN DE LAS PREDICCIONES DE LOS MODELOS DE FOTOIONIZACION MEDIANTE UN ESTUDIO DETALLADO DE LOS COMPLEJOS DE GAS IONIZADO