Search Publications
IUE Observations of Solar-Type Stars in the Pleiades and the Hyades
Linsky, Jeffrey L.; Vilhu, Osmi; Caillault, Jean-Pierre
An extensive set of IUE observations of solar-type stars (spectral types F5-G5) in the Pleiades is presented. Spectra were obtained in January and August 1988 for both the transition region and chromospheric emission wavelength regions, respectively. Mg II fluxes were detected for two out of three Pleiades stars and C IV upper limits for two of th…
Inference of the Extreme-Ultraviolet Continuum Shape of Quasars
Zheng, Wei
The strength of C IV emission in weak-bump QSOs is significantly larger than that in strong-bump QSOs. Equivalent widths of Lyα, Si IV, and C III show no sign of difference between objects with various UV bump strength. The finding suggests that the "big UV bump" is a source of ionization and can be scaled by emission lines. The higher average C I…
Stellar Lyman-Alpha Emission and the Local Interstellar Medium
Simon, Theodore; Landsman, Wayne
The UV spectra now available in the IUE archives have been systematically searched for the presence of Lyman-alpha emission in late-type stars. The results provide the first survey of the behavior of the Ly-alpha emission line across most of the cool half of the H-R diagram. The normalized Ly-alpha emission flux is strongest in the chromospherical…
Circumstellar Material around the Massive Close Binary DH Cephei
Corcoran, M. F.
The expanding atmosphere of the massive close binary DH Cephei is analyzed on the basis of data from ground-based polarimetry and spaceborne UV observations obtained with the IUE satellite. The mass loss from the system is estimated to be about 2 x 10 to the -6th solar mass/yr. This material can be divided into three classes: (1) wind material, wh…
IUE Investigation of Mass Flow in the Interacting Binary U Sagittae
Kondo, Yoji; McCluskey, George E., Jr.; McCluskey, Carolina P. S.
Fifteen far-UV and 13 mid-UV high-resolution spectra of the interacting Algol-type binary U Sagittae have been obtained with the IUE satellite. The resonance lines of Si IV and C IV are present in absorption of moderate strength at all phases. At several phases, weak absorption due to the N V resonance lines is present. The high-temperature pseudo…
The Ultraviolet Spectrum of KX Trianguli Australis
Feibelman, Walter A.
Low-dispersion and high-dispersion IUE satellite observations of the symbiotic star KX TrA, carried out on May 7, 1990, are reported. The low-dispersion data show no significant changes from the observation data obtained a decade ago. Resonantly excited high-excitation Fe II emission lines are seen in the UV spectra of KX TrA, suggesting the exist…
X-Ray Luminosity and Spectral Variability in the Seyfert Type I Galaxy: PG 2130+099
Singh, K. P.; Rao, A. R.; Vahia, M. N.
We present broad-band (0.1-10 keV) X-ray observations of a bright Seyfert I galaxy, PG 2130+099, using the low-energy (LE) and the medium-energy (ME) detectors of the EXOSAT Observatory. The observations were carried out on two occasions separated by a year (in 1984 and 1985), and the X-ray flux was found to have increased by ~35% in the 1.5-6 keV…
X-Ray Observations of the Seyfert 1 Galaxy Markarian 464
Piro, L.; Frontera, F.; Costa, E. +3 more
In this paper we present results of EXOSAT (0.05-10 keV) and hard X- ray (25-45 keV) balloon observations (XG-8 1) of the Seyfert 1 galaxy Mrk 464. The spectrum observed with EXOSAT is well fitted by a power law with a photon spectral index 1.70+/-0.15, in agreement with a previous measurement by HEAO 1 A-2. The absorption column density is found …
Heating Mechanism(s) for Transition Layers in Giants
Bohm-Vitense, Erika; Mena-Werth, Jose
The emission-line fluxes of lines originating in the lower parts of the transition layers between stellar chromospheres and coronas are studied. Simon and Drake (1989) suspect different heating mechanisms for 'hot' and cool stars. Changes in the flux ratios for the C IV to C II emission lines support this suspicion. Large C IV/C II line flux ratio…
Ultraviolet Fe VII Absorption and Fe II Emission Lines of Central Stars of Planetary Nebulae
Cheng, Kwang-Ping; Feibelman, Walter A.; Bruhweiler, Frederick C.
The SWP camera of the IUE satellite was used in the high-dispersion mode to search for Fe VII absorption and Fe II high-excitation emission lines in five additional very hot central stars of planetary nebulae. Some of the Fe VII lines were detected at 1208, 1239, and 1332 A in all the objects of this program, LT 5, NGC 6058, NGC 7094, A43, and Lo …