Search Publications
A Flare Event on the Long-Period RS Canum Venaticorum System IM Pegasi
Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W.
The characteristics of a flare event detected on the long-period RS CVn system IM Pegasi are reported. The low-resolution spectrum show enhancements of up to a factor of five in some emission lines. All of the ultraviolet emission lines normally visible are enhanced significantly more than the normal 30 rotational modulation. Emission fluxes of bo…
An IUE Survey of Activity in Red Giants and Supergiants
Gibson, D. M.; Oznovich, I.
Chromospheric and transition region line activity is examined in apparently single red giants and supergiants using the IUE archives. Low-resolution, large-aperture spectra (mostly short-wavelength) were used to search for variations of emission-line fluxes in time. A series of automatic processing procedures were implemented in order to uniformly…
Identification of Lines in the Satellite Ultraviolet: The Spectrum of Tau Scorpii
Cowley, Charles R.; Merritt, Donald R.
The method of wavelength coincidence statistics (WCS) is applied to the ultraviolet spectra of Tau Sco obtained by the IUE. No identifications of elements heavier than Zn were made. With the exception of Zn IV, all identifications had been previously made in an exhaustive study of Copernicus spectra by Rogerson and Ewell (1985). A comparison of th…
Determination of Photospheric Helium Abundances for the Hot White Dwarfs LB 1663 and CD -38 degrees 10980 from EXOSAT Soft X-Ray Photometry
Heise, J.; Kahn, S. M.; Paerels, F. B. S. +1 more
The photospheric soft X-ray emission of hot (Te> 20,000 K) DA white dwarfs is very sensitive to the composition of the stars' atmospheres. Very small amounts of helium in a hydrogen-dominated atmosphere, amounts which are difficult or impossible to measure at UV and optical wavelengths, can be detected in the soft X-ray band. In this…
Isophotal Diameters of Galaxies at High Redshifts
Weedman, Daniel W.; Williams, Karen L.
New ultraviolet observations and archival spectra are presented for the bright disk of the galaxy NGC 4736 to derive the ultraviolet surface brightness profile. This is used to predict the appearance of such a galaxy at high redshift. The profiles in red light of 100 galaxies determined by S. Kent (1984) are used with assumed ultraviolet spectra t…
X-Ray Observations of the Supernova Remnant N103B in the Large Magellanic Cloud
Singh, K. P.; Westergaard, N. J.; Schnopper, H. W. +1 more
New X-ray observations of the supernova remnant N103B made using the European X-Ray Observatory satellite Exosat and the Einstein Observatory are reported. An X-ray map from Exosat obtained with three different filters corresponding to three different energy bands is presented. The analysis of the X-ray spectra indicates a thermal origin for X-ray…
The Stars with H alpha Missing
Downes, Ronald A.
During the course of a survey for ultraviolet-excess objects, a group of objects were found that spectroscopically resemble the subdwarf B stars, except for variable strength H-alpha absorption. The H-alpha line can have the nominal strength predicted from the other Balmer lines, or it can be completely absent. Observations reveal significant chan…
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 …