Search Publications
The Discovery of Magnetically Controlled Circumstellar Matter in the Helium-weak Stars HD 5737 and HD 79158
Shore, Steven N.; Brown, Douglas N.; Sonneborn, George +2 more
The paper reports the discovery, using combined IUE spectroscopy and Zeeman polarimetric magnetic field measurements, of magnetically controlled circumstellar material in two helium-weak stars. HD 5737 = Alpha Sculptoris is, except for its extreme helium deficiency, similar to the He weak sn star HD 21699. A unique period for the magnetic and C IV…
The Temperature Scale of Hot DA White Dwarfs: Temperatures from Far-Ultraviolet Continuum Fluxes
Basri, Gibor; Bowyer, Stuart; Finley, David S.
Observed far-UV to visible flux ratios of all DA white dwarfs hotter than about 25,000 K are compared with ratios predicted by models in order to derive effective temperatures for the stars. All suitable IUE spectra of seven hot DA white dwarfs for which accurate temperatures based on hydrogen line profiles were available are used to derive a flux…
The Ultraviolet and Visible Light Variability of BP Tauri: Possible Clues for the Origin of T Tauri Star Activity
Simon, Theodore; Vrba, Frederick J.; Herbst, William
BP Tau is a moderate-strength T Tauri star, which has previously been studied photometrically by Vrba et al. (1986, 1989) and shown to have a 7.6-day light cycle. Here, BP Tau was reobserved in order to monitor this star with the IUE satellite. In conjunction with the UV spectroscopy, nearly simultaneous ground-based optical photometry was also ob…
Correlation of X-Ray Burst Properties with Source State in the ``Atoll'' Source 4U/MXB 1636-53
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +3 more
A series of Exosat observations of the 'atoll' source 4U/MXB 1636 - 53 shows that duration and temperature of the X-ray bursts strongly correlate with the X-ray spectral and fast variability characteristics of the persistent emission of the source. This implies that spectral shape, fast variability, and burst duration and temperature all correlate…
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…