Search Publications
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…
The rapid burster and its type II burst profiles.
Stella, L.; van Paradijs, J.; van der Klis, M. +5 more
Type-II bursts with durations ranging from about 2 to about 680 seconds are examined to study burst-peak fluxes, burst intervals, integrated energies, and luminosities associated with MXB 1730-335, the Rapid Burster. The data regarding the bursts are compared to develop general correlations between burst variables, and some general characteristics…
Quasar H-beta profiles and discs.
Penston, M. V.; Perez, E.; Jackson, N.
We present high signal-to-noise spectra of the Hβ region of eight radio-loud quasars in an investigation seeking evidence for the emission of this line from a disc. Although we do not find the double-humped profile expected in simple versions of the disc hypothesis, we do find shoulders in the profile expected in a modified form of this idea. A mo…
SI II emission line diagnostics.
Judge, P. G.; Carpenter, K. G.; Harper, G. M.
The present study compares ratios of Si II UV emission lines in a variety of objects with computations based on recently published collisional data of Dufton and Kingston (1991). A high-quality spectrum of Alpha Tau (K5 III) obtained by Carpenter et al. (1991) is analyzed using the G270M mode of the GHRS on the HST, in addition to high-dispersion …