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…
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…
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…
IUE observations of beta Pictoris : an IRAS candidate for a proto-planetary system.
Kondo, Y.; Bruhweiler, F. C.
The authors have obtained new IUE observations of β Pic, which was identified from IRAS observations as one of the several candidate stars associated with proto-planetary systems (reported by Aumann and colleagues) and whose near-infrared imagery by Smith and Terrile showed an edge-on disk surrounding the star. New high-resolution spectra, when co…
Interstellar dust in the Large Magellanic Cloud.
Martin, P. G.; Clayton, G. C.
This paper presents extensive observations of the properties of interstellar dust in the Large Magellanic Cloud. Extinction and polarization analysis of 12 reddened stars spread across the LMC shows that in the optical and infrared the dust characteristics are remarkably similar to the Galaxy. The wavelength dependence of the polarization and the …
TT ARIETIS : the low state.
Szkody, P.; Shafter, A. W.; Bond, H. E. +3 more
A comprehensive photometric and spectroscopic study of the low state of the novalike variable TT Ari has been made with observations spanning the UV to IR spectral regions. The roughly 5 mag drop in the system's luminosity from the high state indicates that the mass-transfer rate decreased by more than two orders of magnitude. The drastic reductio…