Search Publications
Spectral Synthesis in the Ultraviolet. II. Stellar Populations and Star Formation in Blue Compact Galaxies
O'Connell, Robert W.; Thuan, Trinh X.; Fanelli, Michael N.
Far-UV spectra of seven blue compact galaxies have been obtained with the IUE satellite. These objects span a range in luminosity of -21 <= M_B_ <= -13. We have investigated their stellar content and star formation history by applying the technique of optimizing population synthesis utilizing the library of far-UV stellar spectra developed b…
The Fluorescence of Cometary OH
A'Hearn, Michael F.; Schleicher, David G.
A new solar spectral atlas, improved oscillator strengths, and additional transitions have been incorporated in calculations of the fluorescent equilibrium of the OH molecule in comets as a function of heliocentric distance and radial velocity. Comparisons of detailed, ultraviolet band profiles have been made with the observed, high-resolution spe…
Spatial and Spectral Interpretation of a Bright Filament in the Cygnus Loop
Gull, T. R.; Raymond, J. C.; Hester, J. J. +3 more
A comparison is made of optical and UV line intensities and spatial and spectral optical line profiles of a well-defined Cygnus Loop filament with theoretical models. It is found that the sharp filament is due to the tangency to the line of sight of a large, thick sheet of emitting gas. The emitting region associated with the spur is very deep, an…
Two Lines of Sight with Exceedingly Anomalous Ultraviolet Interstellar Extinction
Savage, Blair D.; Cardelli, Jason A.
Low-resolution IUE data obtained toward HD 62542, a B5 V star in a line of sight associated with a dark cloud in the Gum nebula region near ζ Pup and γ Vel, yield an extinction curve with an extremely broad and weak UV extinction bump and the highest far-UV extinction yet observed in the Milky Way, reaching a value of E(1200-V)/E(B-V) ≈ 15. The we…
Lyman- alpha Emission in Star-forming Galaxies
Huchra, John P.; Geller, Margaret J.; O'Brien, Paul +2 more
We report IUE observations of five blue, low-metallicity, star-forming galaxies sufficiently redshifted to permit detection of Lyα. Two of the galaxies exhibit Lyα emission at modest levels far below the recombination limit; two objects have Lyα in absorption. These observations confirm and extend earlier work which indicates that relatively unevo…
Galactic Interstellar Abundance Surveys with IUE. III. Silicon, Manganese, Iron, Sulfur, and Zinc
Shull, J. Michael; van Steenberg, Michael E.
This paper continues a survey of intestellar densities, abundances, and cloud structure in the Galaxy using the IUE satellite. A statistical data set of 223 O3-B2.5 stars is constructed, including 53 stars in the Galactic halo. It is found that S II lines in B stars, of luminosity classes IV and V, have possible contamination from stellar S II, pa…
A Test of Synthetic Accretion Disk Spectra Using Ultraviolet Flux Distributions of Nova-like Variables
Wade, Richard A.
Ultraviolet (UV) fluxes and other data for a sample of nine novalike cataclysmic variables are assembled from the literature. The UV fluxes and colors are compared to spectra of steady state model accretion disks, constructed using either Planck functions or model stellar atmosphere spectra as elementary radiators. Deficiencies are found with both…
Colliding Stellar Winds in the Eclipsing Wolf-Rayet Binary V444 Cygni
Shore, Steven N.; Brown, Douglas N.
High resolution spectra of V444 Cygni have been obtained using the International Ultraviolet Explorer Satellite. These spectra span both eclipses and include one observation at third quadrature. Together with seven archival spectra, they provide reasonably complete phase coverage for the system. The variations in the P Cygni profiles of the He(II)…
The Abundances of Carbon and Nitrogen in I ZW 18
Garnett, Donald R.; Dufour, Reginald J.; Shields, Gregory A.
We present IUE and McDonald IDS spectrophotometry of the NW H II region in the most oxygen-poor galaxy known, I Zw 18. The C III] λ1909 and [N II] λ6583 emission lines were detected for the first time in this galaxy. Using a photoionization model for the H II region, we derive 12 + log N(X)/N(H) = 6.94 +/- 0.24 for C, 5.99 +/- 0.16 for N, and 7.24…
Measurements of the Gas Temperature and Iron Abundance Distribution in the Coma Cluster
Hughes, John P.; Gorenstein, P.; Fabricant, D.
The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. We find evidence at greater than 95% confidence for a higher temperature in the center of the cluster than in a position approximately 45' off-center. No difference in iron abundance…