Search Publications
The Ly-alpha and C IV lines in 10 low-redshift active galactic nuclei/quasars.
Buson, L. M.; Ulrich, M. -H.
We analyze the properties of the Ly α and C IV lines in 10 active galaxy nuclei/quasars with z < 0.2, for which relatively high quality spectra can be found in the first installment of the IUE "Uniform Low Dispersion Archives". A simple profile fitting of Ly α and of C IV with 2 gaussian components of different widths leads to the following res…
Ultraviolet Fluxes for Globular Clusters in M31: A Rediscussion
Crotts, Arlin P. S.; Cacciari, Carla; Kron, Richard G. +1 more
We discuss long-exposure observations of three bright globular clusters in M31 obtained with both the short- and long-wavelength low-resolution cameras of the International Ultraviolet Explorer satellite. All of the clusters are seen at the longer wavelengths, but only one of the clusters is seen at short wavelengths, and this detection is margina…
Simultaneous observations of the symbiotic star BF Cygni.
Gonzalez-Riestra, R.; Cassatella, A.; Fernandez-Castro, T. +1 more
Simultaneous ultraviolet/optical spectrophotometry and infrared photometry for the low excitation symbiotic star BF Cygni are presented. The analysis of the data suggests that three different components are present in the UV to IR energy distribution. A hot subdwarf with R = 0.48 solar radius and T not less than 60,000 K if the distance is 2.3 kpc…
Constraints on the inner accretion flow of 4U /MXB 1636-53 (V 801 Arae) from a comparison of X-ray burst and persistent emission.
van Paradijs, J.; Wijers, R. A. M. J.; Lewin, W. H. G. +4 more
A detailed analysis is presented of the importance of Comptonization in burst and persistent spectra of the low-mass X-ray binary 4U/MXB 1636-53, and from this analysis it is inferred that the inner accretion flow is geometrically thin. It is found that burst spectra of 1636-53 are very nearly Planckian in shape; from an upper limit to a high-ener…
Cepheid Companions? FM Aquilae, FN Aquilae, RX Aurigae, Y Lacertae, and RS Orionis
Evans, Nancy Remage; Szabados, Laszlo; Udalska, Joanna
IUE spectra have been used to search for companions of FN Aql and RX Aur, two classical Cepheids which have been tentatively identified as binary stars on the basis of cyclic variations in their pulsation periods. Three other Cepheids, FM Aql, Y Lac, and RS Ori, suspected of having blue companions from the (U-B), (B-V) diagram, have also been inve…
Differential Line Development and the Complex Structure of the Broad-Line Region in Fairall 9
Zheng, Wei; O'Brien, Paul T.
We find that the profiles of the UV emission lines Lyα, C IV λ1549, and Mg II λ2798, in the Seyfert 1 galaxy Fairall 9 vary such that the lines are broader when the object is brighter. The profile changes occur mainly near the line center for Lyα and C IV and in the wings for Mg II. These results indicate that the broad-line region (BLR) has a com…
The photospheric temperatures and composition of very hot He-rich white dwarfs.
Barstow, M. A.; Holberg, J. B.
Results are reported from a detailed analysis of Exosat observations of six hot He-rich white dwarfs belonging to, or related to, the spectroscopic subclass of PG1159 stars. These objects are thought to evolve directly from O VI type planetary nebulae nuclei and provide an important link in models of white dwarf evolution. When the Exosat data are…
Accretion behaviour in SS Cygni.
Gaudenzi, S.; Giovannelli, F.; Claudi, R. U. +1 more
The He II (1640 A) equivalent widths are determined from 28 IUE short wavelength low resolution spectra of SS Cygni in quiescence and in outburst. By using the boundary layer model for cataclysmic variables (Patterson and Raymond 1985), the mass accretion rate M(He II) is derived. This mass accretion rate is practically coincident with the rate of…
Coordinated observation of the massive system 4U 1700+24 = HD 154791.
Frontera, F.; Manzo, G.; Robba, N. R. +7 more
The authors report results from multifrequency observations of the X-ray source 4U 1700+24 / HD 154791. This source was observed simultaneously with the EXOSAT and IUE satellites on March 25, 1985, and it is continuously monitored in the optical band at the Bologna Astronomical Observatory since July 1984. Their observations show source features w…
The bimodal spectral and QPO-behaviour of GX 17+2.
Hasinger, G.; Truemper, J.; Langmeier, A.
The spectral and temporal analysis of Exosat observations of the bright galactic bulge source GX 17+2 is presented. The source shows a bimodal spectral and temporal behavior. High-frequency (24-28 Hz) quasi-periodic oscillations (QPO) are found on the horizontal branch of the H-I-diagram. There is evidence for a second harmonic at 50 Hz. QPOs with…