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…
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…
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…
Ultraviolet and Visual Wavelength Spectroscopy of Gas around Eta Carinae
Davidson, K.; Gull, T. R.; Dufour, R. J. +1 more
Observational results of η Carinae are reported, especially spectroscopy of the outer 'S condensation' supplemented by data on the homunculus and its core. Theoretical calculations of atmosphere/wind models and of the shock-heated S condensation are needed for a proper analysis of the data, but some simplified results are discussed. The helium abu…
New Results on the X-Ray Emission and Its Correlation with the Ultraviolet in NGC 4151
Piro, L.; Perola, G. C.; Altamore, A. +8 more
Results from observations of the Seyfert galaxy NGC 4151 obtained with Exosat (0.1-25 keV) and IUE (1200-3000 A) during November 1983, and between December 1984 and January 1985, are presented. The stability of the flux during large-scale variations in the UV and X-ray regions suggests that the soft X-ray excess noted by Holt et al. (1980) represe…
Spectroscopic Studies of Wolf-Rayet Stars. III. The WC Subclass
Conti, P. S.; Massey, P.; Torres, A. V.
Wolf-Rayet (W-R) stars, which are the descendants of massive O-type stars, can be subdivided into three groups depending on their spectral appearance. These groups include the nitrogen class (WN), the carbon class (WC), and the oxygen class (WO). The present paper is concerned with the WC stars. The assignment of WC subtypes has been based on visu…