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The X-ray spectrum of the superluminal quasar 1928+73.
Ghosh, K. K.; Soundararajaperumal, S.
EXOSAT observations (0.1-10 keV) of the radio-loud quasar 1928+73, which displays superluminal motion, were made at four epochs between 1983/283 and 1984/009, and we obtained spectra of this source from the EXOSAT database. The X-ray spectrum (0.1-10 keV) can be explained by a power law and uniform absorption model. No significant low-energy absor…
The radial velocity and binary of X Persei.
Stickland, D. J.
It is shown on the basis of radial velocity measurements on high-resolution spectra of X Persei from the IUE archive that there is no variation above the level of a few km/s and thus no need for a massive unseen component in the system. This does not rule out a neutron star or white dwarf orbiting in the variable wind of the Be star.
How fast is the evolution of the diffuse ultraviolet cosmic background radiation ?
Stanek, Krzysztof Z.
Lyα absorption lines observed in Hubble Space Telescope UV spectra of 3C 273 have neutral hydrogen column densities comparable with those of z ~ 2 quasars. Assuming the standard pressure-confined model of Lyα clouds, we use this fact to determine the evolution of UV background radiation for z < 2. We find that to fit the data the UV background …
EXOSAT observations of clusters of galaxies - I. The X-ray data.
Edge, A. C.; Stewart, G. C.
X-ray observations of 45 clusters of galaxies made with the European X- ray Observatory Satellite, EXOSAT, are presented. The 0.1-20 keV spectra obtained constitute the largest homogeneous spectral sample presently available. Here the analysis of the spectral and imaging data is described. A significant scatter in the correlation between the X-ray…
EXOSAT observations of clusters of galaxies - II. X-ray to optical correlations.
Edge, A. C.; Stewart, G. C.
The results obtained for clusters of galaxies using X-ray data from the European X-ray Observatory Satellite, EXOSAT, are compared with the optical, infrared and radio properties of the clusters taken from the literature. A number of strong correlations are found. The ratios of the intracluster medium (ICM) temperature and the cluster velocity dis…
Compton reflection and the variable X-ray spectrum of NGC 5548.
Nandra, K.; George, I. M.; Hayashida, K. +4 more
Spectral analysis of EXOSAT and Ginga observations of the Seyfert galaxy NGC 5548 has revealed a complex spectral form. At least four components, a steep non-thermal power law, an iron line, a `hard tail' and a soft emission component, have been identified in the 0.05-20 keV range. The soft component arises from thermal emission by optically thick…
Optical and X-ray observations of AO PISCIUM and the origin of the spin pulse in intermediate polars.
Cropper, Mark; Hellier, Coel; Mason, Keith O.
Results are presented of three nights of time-resolved spectroscopic observations and of four Exosat X-ray observations of the AO Psc polar binary. It is found that the AO Psc has a magnetic field much weaker than that of the AM Her star and that it possesses an accretion disc extending inward to about 8 white-dwarf radii and outward to fill the R…
Boundary-layer temperatures in high accretion rate cataclysmic variables.
Drew, Janet E.; Hoare, Melvin G.
The Zanstra method is used to derive limits on boundary-layer temperatures in eclipsing dwarf novae during outburst and nova-like variables, using the observed He II 1640 and 4686 A recombination lines. It is assumed that all the emission is produced in the wind rather than the accretion disk. This method constrains the boundary-layer temperatures…
Two early-type POST AGB stars at high galactic latitudes.
Dufton, P. L.; Keenan, F. P.; Conlon, E. S. +1 more
Two high galactic latitude B-type stars, PHL 1580 and PHL 174, originally identified as distant early-type objects from low-resolution spectroscopy and photometry are re-analyzed using high-resolution spectra. The results of LTE and non-LTE model atmosphere analyses reveal general metal underabundances relative to solar values of typically 0.6 and…
Dust scattering in the high-state eclipse of CEN X-3.
Tennant, A. F.; Day, C. S. R.
Exosat data from two high-state eclipses of Cen X-3 are analyzed for the effects of dust scattering. The light curves show bright (2 per cent of the out-of-eclipse flux), smoothly varying emission which reaches its minimum after mideclipse. Of this emission, the soft flux falls monotonically with orbital phase. This soft component with dust scatte…