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Extinction and Abundance Properties of Alpha Scorpii Circumstellar Grains
Buss, Richard H., Jr.; Snow, Theodore P., Jr.; Gilra, D. P. +1 more
The authors have investigated the ultraviolet extinction and element depletions in the circumstellar envelope of the M supergiant binary system, α Sco, by using IUE, Copernicus, and ANS data of the B dwarf companion, α Sco B, which can be seen in absorption through the cool-star envelope. After assessing the interstellar, circumstellar, and atmosp…
The Ultraviolet Spectra of Intermediate-Redshift Quasars. II.
Huggins, P. J.; Kinney, A. L.; Bregman, J. N. +1 more
This paper completes the analysis of an IUE survey of intermediate-redshift QSOs for which the results on Ly-alpha and continuum properties were given previously. The weaker lines were measured and are discussed in the context of an extended sample including Seyfert galaxies and high-redshift QSOs. The EW(C IV) anticorrelates with the luminosity o…
Studies of Hot B Subdwarfs. V. Continuing Investigation of the C, N, and SI Abundance Patterns in the Atmospheres of sdB Stars
Fontaine, G.; Wesemael, F.; Lamontagne, R.
High-dispersion ultraviolet observations of two hot, hydrogen-rich subdwarfs have been obtained with the IUE observatory and are presented. These data are analyzed with model atmosphere techniques, and element abundances for C, N, and Si are derived. Both PG 0342 + 026 (Te = 21,800 K) and PG 1104 + 243 (Te = 27,200 K) display abundances of these i…
The Low-Luminosity X-Ray Sources in Omega Centauri
Bolte, Michael; Margon, Bruce
The authors report multicolor CCD photometry of the fields of three X-ray sources in ω Centauri; two have very accurate (10arcsec) EXOSAT X-ray positions, in addition to observations from the Einstein Observatory. The crowding in these X-ray fields is moderate and does not preclude accurate photometry of individual objects. Although the data in th…
X-Ray and Optical Observations of X-Ray--selected BL Lacertae Objects
Maccagni, D.; Giommi, P.; Garilli, B. +4 more
Results from several X-ray and optical observations of five X-ray-selected BL Lacertae objects are reported. X-ray light curves covering periods of up to 6 yr reveal that the X-ray flux from these objects does not show large-amplitude trends over this time scale. Variations of up to 2 mag have been observed in the optical. The soft X-ray spectra o…
Spectral Synthesis in the Ultraviolet. I. Far-Ultraviolet Stellar Library
O'Connell, Robert W.; Thuan, Trinh X.; Fanelli, Michael N.
A library of mean stellar energy distributions for use in population synthesis of the ultraviolet spectra of active star-forming galaxies is derived from the ultraviolet spectrophotometry in the IUE Spectral Atlas. The spectra extend from 1230 to 1930 A with a resolution of 6 A. The library contains eight main-sequence groups from O3 to A7 V, four…
Ultraviolet Spectra of HH 1 and HH 2: Spatial Variations and the Continuum Problem
Raga, A. C.; Witt, A. N.; Brugel, E. W. +3 more
High-SNR 12-hr and 14-hr ultraviolet spectra of HH 1 and HH2 in the IUE short-wavelength range are reported. HH 1 data show a (spatial) half-width of the image size in the C IV 1548-A, 1551-A line which is smaller than the spatial half-width for the semiforbidden C II 1907-A, 1909-A line. A qualitatively similar situation is shown for HH 2, althou…
First Unambiguous X-Ray Detection of R Aquarii
Piro, L.; Friedjung, M.; Viotti, R. +1 more
The authors report coordinated ultraviolet and X-ray observations of the symbiotic Mira R Aqr obtained with IUE and EXOSAT in 1985 June and December at phases 0.0 and 0.5 of the Mira light curve. They have detected with the Low-Energy EXOSAT detector a weak X-ray flux of 5.4 and 4.6×10-3 counts s-1 at the two epochs, respecti…
Ultraviolet Spectra and Chromospheres of Cool Carbon Stars
Johnson, Hollis R.; Luttermoser, Donald G.
The authors assemble and discuss all available low-resolution IUE spectra of N-type carbon stars - including TW Hor, BL Ori, UU Aur, NP Pup, U Hya, T Ind, and TX Psc. Identification of spectral features is aided by a composite spectrum. Shortward of 2850 A only emission lines of C II, Mg II, Al II, and Fe II are seen, while the spectrum longward o…
The Problem of V444 Cygni
Underhill, A. B.; Fahey, R. P.
The authors have studied the changes of the spectrum of V444 Cygni (WN5+O6) shown on 13 high-resolution spectrograms obtained with the IUE. Evidence is found for an orbital-phase-dependent "third light" both in line and in continuum wavelengths. A model for the V444 Cygni system consisting of an O star with Teff = 40,000K, R/R_sun; = 10…