Search Publications
The EXOSAT spectral survey of AGN.
Turner, T. J.; Pounds, K. A.
Results are presented from EXOSAT Observations of 48 hard X-ray selected Seyfert type active galactic nuclei (AGN). These include all 30 of the emission line AGN in the Piccinotti sample. Combining EXOSAT LE and ME data has allowed us to obtain X-ray spectra over the broad energy range 0.1 - 10 keV spectra in the ~2-10 keV range are found to be we…
Spin modulated X-ray emission from intermediate polars.
Watson, M. G.; Norton, A. J.
This paper describes a comparative study of all the intermediate polars observed by Exosat. The X-ray pulse profiles of each source are presented, and it is shown that, in all cases, the modulation can be described in terms of an increasing depth with decreasing energy. By considering the pulse phase-resolved spectra, it is shown that the modulati…
Variable X-ray absorption in NGC 4151.
Warwick, R. S.; Yaqoob, T.; Pounds, K. A.
The Seyfert galaxy NGC 4151 was monitored over 20 times by EXOSAT in the period 1983 July-1986 March. The very soft spectral component detected by the EXOSAT low-energy telescope, which may be thermal emission from the narrow-line region of NGC 4151, remained constant over the observing period. In contrast, the medium-energy X-ray continuum emanat…
Iron features in the X-ray spectra of three Seyfert galaxies.
Nandra, K.; Pounds, K. A.; Stewart, G. C. +1 more
Ginga X-ray spectra are presented for three Seyfert type 1 galaxies, each one showing evidence for a significant iron K-emission line. This line is interpreted as fluorescence from cold material, apparently lying close to the plane of the host galaxy, for NGC 5548 (near face-on) and NGC 3227 (~60^deg^ inclination). The additional detection of a la…
EXOSAT observations of X 1822-371 : modelling of the accretion disc rim.
Hellier, Coel; Mason, Keith O.
Data from three Exosat observations have been used to model X1822-371 as an X-ray emitting accretion disk corona (ADC) which is partially obscured by an optically emitting disk whose height varies with azimuthal angle. Using a system inclination of 85 + or - 3 deg and a disk structure parameterized by as few as two straight lines, the model is abl…
Detection of iron features in the X-ray spectrum of the Seyfert I galaxy MCG -6-30-15.
Nandra, K.; Fabian, A. C.; Pounds, K. A. +2 more
The spectra analysis of an extended (~2 d) EXOSAT observation of the Seyfert l galaxy MCG-6-30-15 has revealed significant difference from the previous simple power-law description. In particular, evidence is found for both emission and absorption features from cold iron, indicating a large column density of material possibly located close to the …
The giant haloes of NGC 6543 and 6826.
Walsh, J. R.; Clegg, R. E. S.; Middlemass, D.
Long-slit spectra at several positions on the large faint haloes of NGC 6543 and 6826 were obtained using IPC spectrograph and CCD detectors. It is shown that the halo emission is thermal in origin, and that the forbidden O III electron temperature is higher in each halo than in its central nebula. Halo electron temperature values of 14,700 K for …
The flux and spectral variability of NGC 6814 as observed with EXOSAT.
Branduardi-Raymont, G.; Mittaz, J. P. D.
We present five EXOSAT observations of the Seyfert galaxy NGC 6814 which were carried out over the period 1983 September to 1985 October at intervals of a few months to a year. Over these time-scales the soft X-ray (0.02-2.5 keV) flux of NGC 6814 varies by large factors, decreasing by over and order of magnitude in the first 9 months; this is foun…
Ultraviolet observations of stellar winds in Be and 'normal' B non-supergiant stars.
Prinja, Raman K.
Model profile fits to high-resolution IUE C IV, Si IV, and Si III spectra are used to produce a homogeneous set of wind-velocity and column-density measurements for 40 early-type Be stars and 40 nonemission, nonsupergiant B stars. The mass-loss characteristics in the Be and normal B stars are compared. Results on stellar wind morphology, velocitie…
The absolute magnitudes of RR Lyrae stars - I. X Arietis.
Jameson, R. F.; Fernley, J. A.; Kilkenny, D. +4 more
A Baade-Wesselink analysis based on the infrared flux method of Blackwell and Shallis (1977) is used to estimate the temperature and angular diameter of X Ari at all phases of the pulsational cycle. These results are then used to determine the radius, distance, and absolute magnitude. New UV, optical and IR observations for this metal-poor star ar…