The evolution of an SNR in a high-density medium has been studied using analytical and numerical hydrodynamic and photoionization models. The models show that SNR properties (luminosity, density, size, kinematics, emission line ratios, etc.) are essentially identical to those considered typical of the broad-line region (BLR) of radio-quiet active

Numerical simulations of the response of the broad emission lines in AGN to ionizing continuum variations are presented. The simulations are based on the discrete-cloud model of the broad-line region and employ a 'realistic' continuum light curve. The emission line response light curve and the evolution of the line profile are calculated for a

The optical warps of NGC 5907 is studied by means of CCD photometry, for the U and I filters, as well as for a narrow band filter centered at H-alpha. The present observations were extended out to about 380 arcsec in the NW side and out to about 348 arcsec in the SE side. The H I warps begin at these galactocentric radii, so that the optical ones

Intermediate-resolution spectroscopy in the range 625-775 nm is reported for a faint very-late-type object discovered in two CCD images taken near the center of the Alpha Per cluster. The spectrum shows strong absorption molecular bands, H-alpha emission, and KI absorption typical of late-M dwarfs; H-alpha varies conspicuously. The effective

The results of the 1989 Kaiko-Nankai diving cruise to the eastern Nankai accretionary wedge show that a narrow corridor on the top of a 2000 m deep ridge is characterized by concentrated surface manifestations of fluid seepage and chaotic outcrop orientations, suggesting active faulting along a right-lateral shear zone.Modern biological indicators

The results of one night of observations corresponding to an intensive site assessment campaign, held at the Observatorio del Roque de los Muchachos (La Palma) on July 22 1990, are presented and discussed. The goal of the campaign was to evaluate the contribution of free atmosphere, boundary layer, surface layer and dome + mirror seeing to image