The velocity field of the nearly face-on galaxy NGC 3631, derived from observations in the Hα line and Hi radio line, is analysed to study perturbations related to the spiral structure of the galaxy. We confirm our previous conclusion that the line-of-sight velocity field gives evidence of the wave nature of the observed two-armed spiral structure

Current models of the evolution of the known extrasolar planetary systems need to incorporate orbital migration and/or gravitational interactions among giant planets to explain the presence of large bodies close to their parent stars. These processes could also lead to planets being ingested by their parent stars, which would alter the relative

We explore the dependence of {T_eff}'s and colors of stellar models on the treatment of over-adiabatic convection, both in the atmosphere and in the interior. We compute main sequence, turnoff, and subgiant models for low metallicity stars (Z=2 10-4) using as boundary conditions two new sets of model atmospheres by the Wien group (Kupka \cite{kup96

We present the results of a series of Chandra observations of globular cluster (GC) X-ray sources in M31. Among some 20 GC X-ray sources detected in our M31 observations, 2-3 of them show super-Eddington luminosity (> 1038 erg s-1). It is an interesting fact that the highest X-ray luminosities achieved by Galactic GCs are only several times 1037

The Chandra Multiwavelength Plane (ChaMPlane) Survey is a project to identify a large sample of serendipitous X-ray sources in the galactic plane (|b| ~ 10o), including cataclysmic variables, quiescent low mass X-ray binaries (qLMXBs: including both black hole and neutron star systems), Be X-ray binaries and stellar coronal sources (see Grindlay

Not Available