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 visible and infrared extinction law and the gas-to-dust ratio in the Small Magellanic Cloud.
Bouchet, P.; Lequeux, J.; Prevot, L. +2 more
Photometric observations in the UBVJHK bands have been made for 23 O-B3 stars in the Small Magellanic Cloud, for which the MK spectral type and luminosity class have been determined. Also derived from these data are the extinction curve in the visible and the near-infrared. This curve is very close to the curves in the Galaxy and the Large Magella…
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 hybrid spectrum of the LMC hypergiant R 126.
Stahl, O.; Leitherer, C.; Zickgraf, F. -J. +2 more
An extensive spectroscopic (1150 - 6700 Å) and photometric (UBVRIJHKLMN) study of the peculiar LMC hypergiant R126 has been carried out. The authors derive stellar parameters Teff = 22,500K, R = 72 R_sun; and Mbol = -10.5. The corresponding spectral type is B0.5 Ia+. An estimate of the initial and present mass lead…
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…
Spectrophotometric and model-atmosphere analyses of the hot DO and DAO white dwarfs from the Palomar-Green survey.
Wesemael, F.; Green, R. F.; Liebert, J.
Recent optical and spectrophotometric observations of all currently known DAO and DO hot white dwarf candidates from the Palomar-Green Survey are presented. The optical observations were carried out using the Kitt Peak National Observatory Intensified Image Dissector Scanner (IIDS) system, the Multiple Mirror Telescope (MMT), and two photon-counti…
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…