Search Publications
Broad emission features in QSOs and active galactic nuclei. II. New observations and theory of Fe II and HI emission.
Netzer, H.; Wills, B. J.; Wills, D.
Seven QSOs of low to intermediate redshift are characterized on the basis of: 320-850-nm spectra obtained with the UVITS spectrograph and image-dissector scanner at the f/9 Cassegrain focus of the 2.7-m reflecting telescope at McDonald Observatory; improved model calculations for the Fe II, Mg II, and Balmer lines and the Balmer continuum; and the…
The nucleus of M 82 at radio and X-ray bands : discovery of a new radio population of supernova candidates.
Kronberg, P. P.; Biermann, P.; Schwab, F. R.
Detailed VLA radio maps are presented of the continuum radio emission in M82 and the X-ray emission from the HRI of the Einstein X-ray satellite. The authors have discovered more than 40 new radio sources within 300 pc of M82's nucleus. It is argued that nearly all of these sources are radio supernovae or supernova remnants and their radio luminos…
Galactic interstellar abundance surveys with IUE. I. Neutral hydrogen
Shull, J. M.; van Steenberg, M. E.
A survey is initiated of interstellar densities, abundances, and cloud structure in the Galaxy, using the International Ultraviolet Explorer. From high-resolution (0.1-A) spectra, interstellar column densities are derived toward 244 early-type stars by fitting the damping wings of the Ly-alpha absorption line. Published B-V photometry is used to d…
Interstellar extinction variations in the Large Magellanic Cloud.
Fitzpatrick, E. L.
The properties of ultraviolet interstellar extinction in the Large Magellanic Cloud (LMC) are investigated, with particular emphasis on the issue of regional variability. New IUE observations of reddened and standard stars are combined with existing data from the IUE archives. The author finds essentially identical extinction properties toward 12 …
The evolution of chromospheric activity and the spin-down of solar-type stars.
Simon, T.; Boesgaard, A. M.; Herbig, G.
The authors report on observations made with the IUE satellite of nearly two dozen F7 - G2 dwarfs, dated on the basis of their surface Li content in order to examine the age dependence of ultraviolet chromospheric and transition region emission lines. The IUE data for solar-type stars are compared with observations of T Tauri stars (both published…
Trajectories of charged dust grains in the cometary environment
Horanyi, M.; Mendis, D. A.
Using a simple model of the particles and fields environment of a comet, the trajectories of the smallest (micron- and submicron-sized) dust grains that are expected to be released from a cometary nucleus are calculated. It is shown that electromagnetic forces play a crucial role in the dynamics of these particles. The present calculations indicat…
The gaseous component of the disk around beta Pictoris.
Ferlet, R.; Vidal-Madjar, A.; Gry, C. +2 more
Optical spectra of alpha Lyr, alpha PsA, and beta Pic have been obtained at a velocity resolution of 3 km/s. No circumstellar absorption lines of Ca II or Na I are detected toward alpha Lyr or alpha PsA at sensitive limits. In the favorable case of beta Pic, where the circumstellar disk imaged by Smith and Terrile (1984) is seen nearly edge-on, a …
Winds in central stars of planetary nebulae.
Perinotto, M.; Cerruti-Sola, M.
The physical properties of stellar winds have been studied using the low-resolution IUE spectra for 60 central stars in planetary nebulae. Approximately half of the 42 stars with a measurable stellar continuum displayed P Cygni profiles in UV absorption lines. The appearance of wind was correlated with stellar temperature and radius. Central stars…
The evolution of spiral galaxies and uncertainties in interpreting galaxy counts.
Ellis, R. S.; King, C. R.
Evolutionary models are discussed with respect to the interpretation of faint galaxy counts. The K-corrections are reviewed with available UV data, and the necessary assumptions and model input parameters. In particular the possibility that the bulges of spiral galaxies have evolved in a form similar to that expected for elliptical galaxies is exp…
The discovery of 4.4 second X-ray pulsations from the rapidly variable X-ray transient V 0332+53.
Stella, L.; Parmar, A. N.; White, N. E. +3 more
Using the EXOSAT Observatory, three outbursts from the transient X-ray source V0332 + 53 have been observed between November 1983 and January 1984. It is found that in addition to the rapid Cyg X-1-like variability previously reported by Tanaka et al. (1983), this source also displays stable pulsations with a period of 4.4 s. Doppler variations in…