We discuss the energy budget of AGN jets, based on available data for all 14 having detected optical synchrotron emission. Assuming equipartition between magnetic field and particle energy, these jets transport enough kinetic energy to power a typical extended radio lobe only if the bulk motion of the jet plasma is at least moderately relativistic

There were predictions that blazar OJ 287 should have faded in late 1997 or early 1998. The observational background for these predictions is the sudden fade of OJ 287 in 1989. Back then, the radio flux decreased steadily for 4-5 months and then the brightness dropped also in the optical region suddenly for 2-3 weeks to all time low values, e.g. V

We present the lithium measurements of a continuing programme of light element abundances in metal-poor stars. New equivalent widths of the Li i lambda 670.8 nm resonance line in 67 metal-poor stars covering the metallicity range -3.5

This paper shows how to generalize to non-LTE polarization transfer some operator splitting methods that were originally developed for solving unpolarized transfer problems. These are the Jacobi-based accelerated Lambda-iteration (ALI) method of Olson, Auer, & Buchler and the iterative schemes based on Gauss-Seidel and successive overrelaxation

We present echelle spectroscopy in the 3500 to 10300 Angstroms range for two positions of the galactic H ii region M17. The data have been obtained using the 2.1 m telescope at Observatorio Astronomico Nacional in San Pedro Martir, Baja California. We measure the intensities of 160 emission lines, in particular 36 permitted lines of C(+) , N(0) , N

We present a detailed study of the stellar kinematics in the barred galaxy NGC 5728 based on I-band photometry and long-slit spectroscopic observations in the region of the near-IR Ca II triplet. The analysis of the stellar line-of-sight velocity distribution (LOSVD) has revealed, in the central regions of the bar, the presence of a cold (v/sigma~2