We have obtained new narrowband CCD images, spatially resolved intermediate- and high-dispersion spectroscopic observations of the Ring Nebula (NGC 6720). These data reveal that the bright main nebula is not a real ring, but a closed shell. A prolate ellipsoidal geometry for this shell is inferred from the observed tilts in the [N II] velocity

The continuum and emission lines properties of a sample of 73 blazars is studied, investigating differences and similarities among normal low-polarization quasars (LPQ), radio-loud high polarized quasars (HPQ), and BL Lacertae objects (BLL). We found that at variance with LPQ, most HPQ have power law optical continua (fnu_{prop.to}νalpha^ ) with no

IAUC 6714 available at Central Bureau for Astronomical Telegrams.

AXAF, the Advanced X-ray Astrophysics Facility will be the third satellite in the series of great observatories in the NASA program, after the Hubble Space Telescope and the Gamma Ray Observatory. At launch in fall 1998, AXAF will carry a high resolution mirror, two imaging detectors, and two sets of transmission gratings (Holt 1993). Important

Results from a numerical and analytical investigation of the solution of a nonlinear axisymmetric diffusion equation for the magnetic field are presented for the case when the nonlinear dependence of the diffusivity nu (B) on the magnetic field satisfies basic physical requirements. We find that for sufficiently strong nonlinearity (i.e., for

The star formation history (SFH) and the properties of the dwarf galaxy LGS 3 are analyzed using color-magnitude (CM) diagrams plotted from VRI photometry of 736 stars. The distance to the galaxy is estimated through the position of the tip or the red giant branch. Two acceptable results have been obtained: 0.77+/- 0.07 Mpc and 0.96+/- 0.07 Mpc