We present a kinematical study of the optical ejecta of GK Per. It is based on proper-motion measurements of 282 knots from ~20 images spanning 25 years. Doppler shifts are also computed for 217 knots. The combination of proper motions and radial velocities allows a unique three-dimensional view of the ejecta to be obtained. The main results are as

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.