We present high and low resolution spectroscopic observations for a sample of seven ring nebulae around Wolf-Rayet (WR) stars in M33: MC 27, MC 44, MC 46, MC 51, MC 57, MC 65, and MC 70. An analysis of the ionization structure of the nebulae indicates that photoionization is the main source of excitation. Physical conditions and abundances have

Supernova 1993J (SN 1993J) in M81, now classified as Type IIb, is a strongly emitting radio supernova whose size can be resolved and whose growth can be monitored with the technique of very long baseline interferometry (VLBI). The results could provide important information about the circumstellar matter and the degree of asymmetry of the explosion

We present deep charge coupled device (CCD) imaging of the low-luminosity radio galaxy B2 1243+26 which contains a two-sided, well-defined radio jet at the kpc scale. The galaxy is located in a region of high galactic density and has a nearby companion of similar luminosity. At approximately 10 kpc from the nucleus of the galaxy, we detect optical

A thorough analysis of the sensitivities of the four Stokes profiles to the physical quantities involved in the local thermodynamic equilibrium (LTE) line formation is presented. We point out the ambiguities on the definition of a mean depth of formation of a given spectral line and on the use of Contribution Functions for the ascription of a

IAUC 5945 available at Central Bureau for Astronomical Telegrams.

We present spectropolarimetric observations of a sample of three quasars selected because of their very different broad-band polarization properties. All of the objects in the sample show frequency-dependent polarization degree (FDP), and two of them also show frequency-dependent polarization position angle (FDPA). We have not detected polarization