Search Publications
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…
A survey of the galactic plane with EXOSAT.
Warwick, R. S.; Watson, M. G.; Turner, M. J. L. +2 more
The distribution of 2 - 6 keV X-ray emission in the galactic plane in the first and fourth galactic quadrants has been measured in a series of scanning observations with the medium-energy proportional counters on EXOSAT. The results are presented as contour maps and in the form of a catalogue of 70 discrete sources.
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…
Cometary gas and plasma flow with detailed chemistry.
Huebner, W. F.; Wegmann, R.; Schmidt, H. U. +1 more
This paper describes recent hydrodynamic and magnetohydrodynamic (MHD) simulations for the gas and plasma flow around a comet with detailed photo and chemical reaction network of 59 neutral and 76 ionized chemical species. The method allows for a separate energy balance of the electrons, separate flow of neutral gas, fast neutral atomic and molecu…
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…
The beta Pictoris circumstellar disk. VI. Evidence for material falling on to the star.
Ferlet, R.; Vidal-Madjar, A.; Lagrange-Henri, A. M.
New archive observations with International Ultraviolet Explorer are used to study the temporal variations of the circumstellar absorption towards β Pictoris. The authors first show that strong variations occur in the redshifted part of the resonance lines of Al III, Mg II, and Fe II, and also of metastable lines of Fe II. These variations are the…
Relative C, N, O abundances in red giants, planetary nebulae, novae and symbiotic stars.
Vogel, M.; Nussbaumer, H.; Schild, H. +1 more
C/N and O/N abundance ratios deduced from UV data are presented for 24 symbiotic stars. There is little scatter in these ratios, indicating that the symbiotic phenomenon only occurs in a well defined evolutionary stage. Comparison with related objects such as red giants, novae, and planetary nebulae reveals that symbiotic objects best fit the CNO …
The ultraviolet continuum of quasars -I. The shape of the continuum, continuum reddening and intervening absorption.
Wilson, R.; Gondhalekar, P. M.; Obrien, P. T.
We present ultraviolet data for a sample of 81 quasars covering a wide redshift and luminosity range. After allowing for the effect of absorption due to intervening clouds, the intrinsic optical and ultraviolet continuum for quasars is found to steepen towards shorter wavelengths from ~ 1 micron to ~800 A by ~1 in spectral index. The mean ratio of…