Search Publications
Chromospheric-Coronal Activity at Saturated Levels
Walter, Frederick M.; Vilhu, Osmi
High-resolution IUE observations of Mg II emission lines in W Ursae Majoris were obtained. In addition, estimates of the Mg II emission for other F-type contact binaries were obtained using archival high-resolution k line spectra and some nonstandard methods; the available data were compiled for Mg II, C IV, and X-ray emission in main-sequence F, …
Highly Ionized Interstellar Gas Located in the Galactic Disk and Halo
Savage, Blair D.; Massa, Derck
High-resolution IUE absorption line spectra have been obtained for 40 distant stars in order to study the distribution of interstellar H I, Si IV, C IV, and N V in the Galactic disk and lower halo. Respective midplane densities of 2 x 10 to the -9th, 7 x 10 to the -9th, and 3 x 10 to the -9th are found for Si IV, C IV, and Ni V. Both column densit…
The Planetary Nebula NGC 3918
Harrington, J. P.; Walsh, J. R.; Barlow, M. J. +1 more
A detailed study of the planetary nebula NGC 3918, based on UV, optical, and radio observations, is presented. The central star has a predicted V magnitude of 14.6 and a luminosity of 6000 solar luminosities for a distance of 1.5 kpc. A contour map of the nebula in H-beta light is given. Velocity profiles of forbidden O II optical lines show that …
X-Ray Spectra of PG Quasars. II. The X-Ray--Ultraviolet Excess of PG 1211+143
Elvis, Martin; Green, Richard F.; Bechtold, Jill +2 more
Observations of the quasar PG 1211 + 143 are presented and its continuum is modelled in terms of an accretion disk and an underlying power law. The X-ray spectrum in the Einstein imaging proportional counter band is well described by a power law with the very steep spectral index 2.2 + or - 0.4. The overall continuum spectral energy distribution c…
A Detailed Study of the C IV lambda 1550 Line Profile and Adjacent Spectral Features in NGC 4151 from 1978 to 1983
Perola, G. C.; Altamore, A.; Boksenberg, A. +7 more
The 1450 - 1720 Å spectral region of NGC 4151 is analyzed by means of Gaussian decomposition for 69 different epochs, from early 1978 to the end of 1983. The C IV λ1550 emission profile is well represented by a core, whose full width at half-maximum varies between 2600 and 5500 km s-1, and an ultrabroad component (14,600 km s-1
IUE Observations of the Dwarf Nova HL Canis Majoris and the Winds of Cataclysmic Variables
Raymond, John C.; Mauche, Christopher W.
In order to investigate the nature of the winds of cataclysmic variables the authors present an observational and theoretical study of the P Cygni profiles of these systems, giving particular attention to the profiles of the dwarf nova HL CMa. After presenting the IUE observations of HL CMa, the authors give the results of a synthetic spectral cod…
Ultraviolet Observations of SN 1987A
Kirshner, Robert P.; Sonneborn, George; Crenshaw, D. Michael +1 more
UV observations of the supernova in the LMC, SN 1987A, were carried out with the IUE satellite. The earliest data show that the UV flux from the supernova was already declining while the optical flux was still rising. The UV spectrum at these epochs consists of broad features associated with the supernova atmosphere punctuated by sharp interstella…
The Dependence of Ultraviolet Chromospheric Emission upon Rotation among Late-Type Stars
Simon, Theodore; Fekel, Francis C., Jr.
The authors have obtained low-resolution IUE spectra of a large number of chromospherically active stars. Integrated fluxes of chromospheric and transition region emission lines have been measured. These fluxes, supplemented by published observations and measurements of IUE archival spectra, have been used to search for correlations between activi…
Physical Parameters for 12 Planetary Nebulae and Their Central Stars in the Magellanic Clouds
Gull, Theodore R.; Aller, Lawrence H.; Maran, Stephen P. +3 more
Nebular and central star parameters and elemental abundances of C, N, O, Ne, S, and Ar are presented for the planetary nebulae N2, N5, N43, N54, and N67 in the SMC and P2, P7, P9, P25, P33, and P40 in the LMC. The nebular chemical compositions are affected by nuclear processes in the precursor stars, which may not have been sufficiently massive to…
Highly Ionized Stellar Winds in Be Stars: The Evidence for Aspect Dependence
Grady, C. A.; Snow, T. P.; Bjorkman, K. S.
The authors present the results of an ultraviolet survey of stellar winds in 62 Be and 43 normal B stars covering spectral types B0.5 - B5 and luminosity classes V - III. They find that the wind absorption seen in the resonance lines of C IV, Si IV, and Si III in Be stars is often the result of blended absorption from multiple shortward-shifted di…