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Color Excesses, Intrinsic Colors, and Absolute Magnitudes of Galactic and Large Magellanic Cloud Wolf-Rayet Stars
Vacca, William D.; Torres-Dodgen, Ana V.
Using IUE archival data in the wavelength range 1200-3200 A, we have developed a new quantitative method of nulling the 2175 A interstellar absorption feature observed in stellar spectra and have used this method to determine the color excesses and UV spectral indices for 44 Galactic and 32 Large Magellanic Cloud (LMC) Wolf-Rayet stars. In order t…
Multi-wavelength observations of 3C 273. II. 1986-1988.
Bouchet, P.; Falomo, R.; Walter, R. +9 more
Multi wavelength observations of 3C273 started in 1983. Since then data have been obtained from the radio end of the spectrum to the X-rays at more or less regular intervals. The sampling of the radio, near IR, visible and UV domains has greatly improved since 1985 and 1986, allowing useful cross-correlation analysis of the different components. A…
Abundances from B stars of the Magellanic Clouds.
Stahl, O.; Wolf, B.; Reitermann, A. +1 more
Model atmosphere analyses of two B giants, NGC 1818/D 12 and NGC 330/3, which are probably members of blue globular clusters of the LMC and SMC, respectively, are carried out. The analyses are based on CASPEC spectrograms (resolution ~20.000 S/N >/~ 50), on IUE low dispersion spectrograms (both SWP and LWP) and on UBVRI photometry. The analysis…
Evidence for a Supermassive Black Hole in the Nucleus of the Seyfert Galaxy NGC 5548
Crenshaw, D. Michael; Blackwell, James H., Jr.
The international campaign to monitor the variable Seyfert 1 galaxy NGC 5548 with the International Ultraviolet Explorer (IUE) has provided an extensive and well-sampled set of spectroscopic observations. These observations are used to study the response of the C IV λ1550 emission-line profile to changes in the photoionizing continuum. Near the en…
PG 1553+11 : a bright optically selected BL Lacertae object.
Treves, Aldo; Falomo, Renato
A detailed study of the bright optically selected BL Lac object PG 1553 + 11 is presented. UV observations, obtained during a high state of the source, together with simultaneous optical spectrophotometry and near-IR photometry, allow the spectral flux distribution to be examined from 8 x 10 to the 13th to 2.5 x 10 to the 15th Hz. This distributio…
The Strength of Optical Fe II Emission in Quasi-stellar Objects
Zheng, Wei; O'Brien, Paul T.
Based on optical data for a sample of 33 QSOs taken from Wilkes and Elvis, we study the relation between the strength of optical Fe II emission, the line widths, and the soft X-ray spectrum. The previously claimed relation that objects with flat soft X-ray spectra have weak optical Fe II emission is not present for this sample. A strong relation e…
Camera Artifacts in IUE Low-Dispersion Spectra
Crenshaw, D. Michael; Norman, Dara J.; Bruegman, Otto W.
Sky-background images obtained by the International Ultraviolet Explorer (IUE) were analyzed to study artificial spectral features (camera artifacts) in low-dispersion spectra. The artifacts mimic emission features and have been present in long-exposure spectra since the launch of the IUE satellite. The camera artifacts are strong in spectra chara…
The ephemeris of X 1822-371.
Hellier, Coel; Mason, Keith O.; Smale, Alan P. +1 more
From the analysis of eclipses observed with the HEAO-1, Einstein, Exosat and Ginga satellites, it is shown that the orbital period of X1822 - 371 is increasing on a time-scale of 2.9 million yr. The period change, one of only three determined amongst the LMXBs, is in the opposite sense to the expected evolutionary trend, but in the same sense as t…
Chromospheres of Metal-deficient Field Giants
Smith, Graeme H.; Dupree, A. K.; Hartmann, L.
Observations of the 2800-A Mg II line have been obtained with IUE for a sample of 10 metal-deficient field giant stars to search for chromospheric emission and signatures of mass loss, as well as to establish the level of chromospheric radiative energy losses from these stars. Mg II emission is probably present in all stars. High-resolution spectr…
Spectral Synthesis in the Ultraviolet. III. The Spectral Morphology of Normal Stars in the Mid-Ultraviolet
O'Connell, Robert W.; Burstein, David; Wu, Chi-Chao +1 more
The morphology of 218 mid-UV spectra of stars ranging from O through K in spectral type is examined. Several new line and continuum indices are defined and their usefulness as temperature, luminosity, and metallicity discriminants is discussed. Mid-UV stellar continua are found to be markedly affected by abundance. A UV excess, delta(2600-V), is c…