Optical and radio data from the 1989 minimum are analyzed to examine the implications of the light curves for the spectrum. The optical spectrum increases between maximum and minimum with a sharp peak in the continuum, and a normal shape is noted at the minimum. The data are suggestive of a self-absorbed synchrotron component in the accretion disk

We analyse age-velocity dispersion relations (AVRs) from kinematics of individual stars in eight Local Group galaxies ranging in mass from Carina (M* ˜ 106 M⊙) to M31 (M* ˜ 1011 M⊙). Observationally the σ versus stellar age trends can be interpreted as dynamical heating of the stars by giant molecular clouds, bars/spiral arms or merging subhaloes

The mechanism causing breaks in the radial surface-brightness distribution of spiral galaxies is not yet well known. Despite theoretical efforts, there is not a unique explanation for these features and the observational results are not conclusive. In an attempt to address this problem, we have selected a sample of 34 highly inclined spiral

We report atmospheric parameter estimates (Teff, log g, [Fe/H]) and other information (radial velocities, proper motions, distance estimates) for roughly 40,000 stars (out of a total of some 75,000) from the third public release of the Sloan Digital Sky Survey (SDSS), DR-3. As part of this exercise, we have compiled a set of spectral templates that

We briefly communicate about 21st run of the Whole Earth Telescope (WET) in April 2001, where the eclipsing short period binary sdB system PG 1336-018 was the primary target.

Absorption line-strengths have allowed us to carry out a comprehensive stellar populations analysis, providing very strong constraints for discriminating and constraining current galaxy formation scenarios. I describe the main features of this approach, pinpointing the most popular indices and diagnostic diagrams, and the main problems affecting