Since the 1960s, ground-based radio astronomers have had the capability to image solar radio emissions using aperture synthesis techniques. These images show the two-dimensional time history of CME-driven shock fronts, for example. However, ground-based observations are limited by the terrestrial ionosphere to frequencies above about 15 MHz, which

We have measured the equivalent width WK of the K i resonance line at 7699 Angstroms for a large sample of low activity late-type stars observed with high spectral resolution and we have verified that the relation WK vs. Teff is monotonically decreasing, for both dwarf and giant stars. This behaviour is different from that of the Na I D lines for

We report YALO consortium observations using the Yale 1-m telescope at CTIO and observations with the 48" telescope at the Whipple Observatory: Aql X-1 = V1333 Aql appears to be beginning a new outburst. This x-ray binary outbursts approximately once per year, and based on its recent outbursts was due to erupt.

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