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 …
The Discovery of 3.8 Hour Periodic Intensity Dips and Eclipses from the Transient Low-Mass X-Ray Binary EXO 0748-676
Parmar, A. N.; White, N. E.; Giommi, P. +1 more
Using the EXOSAT Observatory the authors have discovered a new transient X-ray burst source EXO 0748-676 that shows 8.3 minute duration X-ray eclipses that recur with a period of 3.82 hr. If the companion star is on the main sequence, the eclipse duration gives a companion mass of 0.45 M_sun; and a system inclination of 75°. Irregular intensity di…
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 and Optical Observations of the Ultrashort Period Dwarf Nova SW Ursae Majoris: A Likely New DQ Herculis Star
Szkody, P.; Shafter, A. W.; Thorstensen, J. R.
Optical photometric and spectroscopic and X-ray observations of the dwarf nova SW UMa are presented. Moderate resolution spectroscopic data have established an orbital period of 81.8 min and have revealed that the Balmer emission lines have a multiple structure. A narrow component, similar to the s-wave component which is sometimes seen in catacly…
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…