We have studied the host galaxies of a sample of radio-loud active galactic nuclei (AGNs) spanning more than 4 decades in the energy output of the nucleus. The core sample includes 40 low-power sources (BL Lac objects) and 22 high-power sources (radio-loud quasars) spanning the redshift range 0.15

We analyze Space Telescope Imaging Spectrograph (STIS) spectra in the 1150-1700 Å wavelength range obtained for six early B supergiants in the neighboring galaxy M31. Because of their likely high (nearly solar) abundance, these stars were originally chosen to be directly comparable to their Galactic counterparts and represent a much needed addition

Horizontal velocities and their temporal variations inside a large pore and in the surrounding granulation are studied from a 73 min sequence of white light frames, acquired at the Swedish Vacuum Solar Telescope (La Palma). The local correlation tracking technique with high spatial (0farcs 31) and temporal (5 min) resolution was applied to

We examine the influence of non-adiabatic effects on the modes of an isothermal stratified magnetic atmosphere. We present new solutions for magneto-acoustic-gravity (or MAG) waves in the presence of a radiative heat exchange based on Newton's law of cooling. An analytic expression for the dispersion relation is derived, which allows the effect of

We examine the impact of discrete numbers of stars in stellar populations on the results of Chemical Evolution Models. We explore the resulting dispersion in the true yields and their possible relation with the dispersion in observational data based on a Simple Closed-Box model. In this framework we find that the dispersion is larger for the less

We have pursued two different methods to analyze the old stellar population near the Galactic plane, using data from the 2MASS survey. The first method is based on the isolation of the red clump giant population in the color-magnitude diagrams and the inversion of its star counts to obtain directly the density distribution along the line of sight