Search Publications
PG 1700+518 : a low-redshift, broad absorption line QSO.
Boksenberg, A.; Pettini, M.
The first high-resolution optical spectra and lower resolution UV spectra of PG 1700 + 518, the only known broad-absorption-line (BAL) QSO at low emission redshift (0.288) are presented. The optical data were obtained with the Isaac Newton Telescope on the island of La Palma and the UV data with the International Ultraviolet Explorer satellite. Th…
Ultraviolet spectral morphology of the O stars. III. The ON and OC stars.
Walborn, N. R.; Panek, R. J.
Key regions in the 1200-1900-A spectra of two ON dwarfs and four ON/OC supergiants are illustrated and discussed, using high-resolution data from the International Ultraviolet Explorer archives. Marked anomalies are displayed by both stellar wind and photospheric C and N features, relative to the consistent framework provided by normal ultraviolet…
The X-ray spectrum of the supernova remnant W 49B from EXOSAT.
Jones, L. R.; Smith, A.; Pye, J. P. +1 more
X-ray observations of the supernova remnant W49B made by the medium-energy detector and gas scintillation propotional counter experiments on board Exosat are presented. The detection of a very strong emission line feature at 6.7 keV indicates a thermal origin of the X-rays. Fitting the spectral data with an optically thin thermal plasma model indi…
Detection and analysis of photospheric CNO features in the ultraviolet spectrum of the hot DO white dwarf PG 1034+001.
Sion, E. M.; Wesemael, F.; Liebert, J.
An analysis of PG 1034 + 001 extended to include the high-dispersion IUE spectra and the high-resolution optical multiple-mirror telescope echelle spectra is discussed. The observations reveal the presence of absorption lines (C IV at 1548 and 1551 A, N V at 1238 and 1242 A, and O V at 1371 A) from highly ionized species with large redshifts (+ 40…
Ultraviolet absorption by highly ionized halo gas near the galactic center.
Savage, B. D.; Massa, D.
As part of a program to survey highly ionized gas in the Milky Way disk and halo, the authors have obtained high-resolution IUE far-UV spectra of 12 stars at galactocentric distances less than 6 kpc. The stars are 0.7 - 2.2 kpc away from the plane. Most of the spectra contain exceedingly strong and broad interstellar absorption lines of weakly and…
Studies of hot B subdwarfs. III. Carbon, nitrogen and silicon abundances in three sdB stars.
Fontaine, G.; Sion, E. M.; Wesemael, F. +1 more
Optical and high-dispersion IUE observations of three hot B subdwarfs (UV 1758 + 36, Ton S-227, and Feige 65) are presented. These data are analyzed with model atmosphere techniques, and element abundances for C, N, and Si are derived. The abundances are either near (N) or below (C, Si) the solar value; large variations (1) in the extent of undera…
Stratification of the Extended Atmosphere of the Wolf-Rayet Component of V444 Cygni
Cherepashchuk, A. M.; Eaton, J. A.; Khaliullin, Kh. F.
The authors have obtained ultraviolet spectra covering both eclipses of V444 Cyg. Striking atmospheric eclipses, of up to 0.7 mag in depth, were detected in individual strong lines as well as over large ranges of the continuum shortward of 1500 Å. The continuum in the 1560 - 1900 Å range is produced by electron scattering. At shorter wavelengths e…
He II lambda 1640/lambda 4686 and Lyalpha/Hβ ratios in the extraordinary Seyfert galaxy Markarian 359.
Davidson, K.; Gull, T. R.; MacAlpine, G. M. +1 more
The exceptionally narrow-lined Seyfert 1 galaxy Mrk 359 is ideally suited for determining reddening via the He II lambda 1640/lambda 4686 emission-line ratio. Here the validity of He II lines as a reddening indicator for quasars and Seyfert galaxies is reexamined and confirmed in the context of the most complete photoionization models available. I…
Carbon IV absorption troughs in the ultraviolet spectra of Be stars :gone with the wind ?
Marlborough, J. M.; Barker, P. K.
IUE observations of five Be stars reveal striking and previously unrecognized forms of stellar wind variability. Broad C IV double-lambda 1548,1550 absorption troughs, which underlie shortward-shifted narrow absorption components, may disappear or reappear. The C IV equivalent width can vary by a factor approximately equal to or greater than 5 on …
IUE observations of amorphous hot galaxies.
Hunter, D. A.; Lamb, S. A.; Gallager, J. S., III +1 more
Blue amorphous galaxies are star-forming, irregularlike systems which lack the spatially distinct OB stellar groups that are characteristic of most late-type galaxies. In order to better understand the nature of star-formation processes in these unusual galaxies, short-wavelength IUE spectra of the amorphous galaxies NGC 1705 and NGC 1800 have bee…