Search Publications
Line Variations in Quasars and Seyfert Galaxies
Gaskell, C. M.; Sparke, L. S.
Quantitative estimates of the sizes of broad-line regions in three well-studied Seyfert I galaxies are presented, and differences between these and previously reported size estimates for NGC 4151 are discussed. Both Lick Observatory and IUE satellite data on NGC 4151 are analyzed, and it is shown that both are consistent with the high-ionization f…
The atmosphere of subluminous B stars. II. Analysis of 10 helium poor subdwarfs and the birthrate of sdB stars.
Heber, U.
Ultraviolet and visual spectra of 10 helium-poor hot subluminous subdwarfs are analyzed, and the birthrate of these stars is determined. Effective temperatures range from 25,000 - 75,000 K in the group, which includes three binaries. sdB's occupy a narrow range in gravities and photospheric helium content in contrast to the sdOB ranges of gravitie…
Spectral Energy Distributions of Active Galactic Nuclei between 0.1 and 100 Microns
Malkan, M. A.; Edelson, R. A.
The authors have combined new photometry from IRAS with ground-based optical and near-infrared spectrophotometry and ultraviolet spectrophotometry from IUE to study the spectral energy distributions from 0.1 to 100 µm for 29 active galactic nuclei. After correcting for the effects of starlight and foreground and internal reddening, the autho…
An Analysis of the Shapes of Ultraviolet Extinction Curves. I. The 2175 Angstrom Bump
Fitzpatrick, E. L.; Massa, D.
IUE data are used to investigate the properties of the 2175 A interstellar extinction bump toward 45 reddened Milky Way stars. Using analytic fitting functions, parameters are derived which describe the central position, FWHM, and strength of the bump. The bump position is very stable, with an extreme deviation which is still significantly larger …
Radio Emission from Galactic Wolf-Rayet Stars and the Structure of Wolf-Rayet Winds
Churchwell, E.; Abbott, D. C.; Torres, A. V. +1 more
The authors have observed 23 Wolf-Rayet stars with the VLA at 6 cm and reobserved four stars at both 2 and 6 cm. When combined with previous data, these observations form an essentially complete sample of 40 W-R stars within a distance of 3 kpc and north of declination -47°. Available measurements of optical emission lines are used to estimate the…
An average interstellar extinction curve for the Large Magellanic Cloud.
Fitzpatrick, Edward L.
In a recent paper (Fitzpatrick, 1985) the author examined the properties of ultraviolet interstellar extinction curves in the Large Magellanic Cloud (LMC) utilizing International Ultraviolet Explorer observations of 19 reddened O and B type LMC supergiants. The author has now obtained IUE observations of an additional eight reddened LMC OB supergi…
A Survey of Chromospherically Active Stars
Fekel, F. C.; Henry, G. W.; Moffett, T. J.
Photometric and/or spectroscopic observations have been obtained of 52 late-type stars which are suspected or known to be chromospherically active. Although not all types of observations were obtained for each star, these observations include all-sky BVRI Johnson photometry, ultraviolet spectrograms, low-dispersion blue-wavelength spectrograms, an…
Active Extragalactic Sources: Nearly Simultaneous Observations from 20 Centimeters to 1400 Angstrom
Landau, Robert; Golisch, Bill; Jones, Terry J. +15 more
IRAS, IUE, and ground-based optical, NIR, mm and submm, and radio observations obtained mainly on Apr. 9-23, 1983, are reported for 19 active extragalactic sources and eight control sources. The overall spectra of the compact active sources are shown to be well represented by continuous-curvature functions such as parabolas. The spectra are found …
IUE Spectra and a Resulting Model of Seyfert 2 Galaxies
Ferland, G. J.; Osterbrock, D. E.
Nearly simultaneous optical and ultraviolet observations of several Seyfert 2 galaxies are presented. A mean optical to ultraviolet emission line spectrum for Seyfert 2 galaxies is determined, and these intensities are compared with predictions of photoionization models. The UV to X-ray nonthermal continuum which ionizes this gas is examined. The …
X-Ray Sources in Regions of Star Formation. I. The Naked T Tauri Stars
Walter, F. M.
Einstein X-ray observations of regions of active star formation in Taurus, Ophiuchus, and Corona Australis show a greatly enhanced surface density of stellar X-ray sources over that seen in other parts of the sky. Many of the X-ray sources are identified with low-mass, pre-main-sequence stars which are not classical T Tauri stars. The X-ray, photo…