Search Publications
The carbon and nitrogen abundances in WN and WC Wolf-rayet stars.
Willis, A. J.; Smith, L. J.
New ultraviolet spectroscopy obtained with the IUE satellite of helium, carbon and nitrogen lines in six WN and four WC stars have been analysed using non-LTE Escape Probability techniques to derive the stellar atmospheric C/N, C/He and N/He ratios. The derived C/N ratio is found to lie in the range: 0.02-0.06 for WNE stars; 0.006-0.04 for WNL sta…
Discovery of highly ionized species in the ultraviolet spectrum of Feige 24.
Raymond, J. C.; Dupree, A. K.
A high-resolution ultraviolet spectrum of the nearby (90 pc) white dwarf binary Feige 24 (DA + M1-2 V) obtained with the International Ultraviolet Explorer satellite (IUE) reveals two sets of absorption features in the species C IV, Si IV, and N V. The low-velocity component (V approximately 1 km/s) arises from the local interstellar gas apparentl…
OH fluorescence in comets - Fluorescence efficiency of the ultraviolet bands
A'Hearn, M. F.; Schleicher, D. G.
The present investigation is concerned with the calculation of the fluorescence efficiency of OH over a wide range of heliocentric radial velocities. Three vibrational states in each of the two lowest electronic states are included in these calculations, producing a total of nine vibrational bands in the ultraviolet. The attempt is made to reprodu…
A study of element depletions in interstellar gas.
Gondhalekar, P. M.; Pettini, M.; Phillips, A. P.
Optical and ultraviolet studies have shown that most elements in the gas phase of the interstellar medium are underabundant relative to the solar composition. The missing gas atoms are assumed to be contained in interstellar grains. The study of the depletion of interstellar elements in the gas phase provides, in this connection, a means for study…
Energy distribution in the strongly interacting binary system SX Cas.
Weiland, J. L.; Koch, R. H.; Plavec, M. J.
IUE spectra and optical scans covering the 110-680 nm interval were obtained in a search for a source which would resolve the anomalous presence of strong Balmer emission lines in the SX Cas eclipsing binary system, which is inconsistent with the usual spectral classification of the components as A6 III + G6 III. The IUE spectra unexpectedly show …
Two multifrequency observations of the BL Lacertae object OJ 287
Bruhweiler, F. C.; Sitko, M. L.; Worrall, D. M. +8 more
Results are reported for various sets of X-ray, UV, visual, IR, millimeter, and radio observations of OJ 287. The spectral information is used to constrain nonthermal energy production models for the source, and three possible models are considered. It is found that, in order to describe all the observed flux in the radio to X-ray bands with a syn…
IUE observations of dwarf novae during active phases.
Stahl, O.; Vogt, N.; Wolf, B. +4 more
Spectra of six dwarf novae during active phases were observed with the IUE in the low resolution mode in order to study different types of outburst behavior and to investigate physical processes during outbursts. Results were obtained for continuum energy distribution and interstellar extinction, temperatures and spectral indices, line spectra, an…
SK 143 : an SMC star with a galactic-type ultraviolet interstellar extinction.
Lequeux, J.; Prevot, L.; Prevot-Burnichon, M. -L. +2 more
The ultraviolet extinction curve (1200-3000 A) deduced from IUE observations of the Small Magellanic Cloud star Sk 143 is presented. This curve is rather similar to the galactic one, with a large bump at 2200 A and a smaller rise shortward of 2000 A compared to the SMC extinction curve of Rocca-Volmerange et al. (1981). The N(H)/E(B-V) ratio estim…
Magnetic structure in cool stars. V. Chronospheric and transition-region emission from giants.
Zwaan, C.; Oranje, B. J.; Middelkoop, F.
The outer atmospheres of giants at larger heights than the low chromosphere, where the Ca II H and K lines are formed, are studied. In particular, the coupling between the upper chromosphere and the transition region is investigated. G and early K-type giants of different Ca II H and K line-core flux were selected for observations with the IUE. Th…
LB 3459 - an O-type subdwarf eclipsing binary system. Non-LTE analysis of the primary.
Kudritzki, R. P.; Kilkenny, D.; Lynas-Gray, A. E. +2 more
A non-LTE analysis is presented for the primary component of the sdO eclipsing binary LB 3459. The results of the analysis give Teff = 40,000+3000-2000 K, log g = 5.3±O.2 (cgs) and a surprisingly low helium abundance of y = 0.3+O.2-0.1% by numbers. LB 3459 appears to be the result of mass exch…