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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…
Absorption dips and the properties of the accretion stream in polars.
Motch, C.; King, A. R.; Watson, M. G. +1 more
Simultaneous X-ray, optical and infrared observations of the absorption dips in the polar system EF Eri are presented. These observations are used to determine the properties of the dips and develop a simple model for the dips in which they are caused by absorption in the accretion stream as it crosses the line-of-sight to the X-ray/optical emissi…
On the nature of the old nova CP Puppis.
O'Donoghue, D.; Wargau, W.; Warner, B. +1 more
Results are reported from nearly 48 h of high-speed photometry of the ex-nova CP Pup, obtained at Sutherland or Mount Stromlo, and 23 h of spectroscopic coverage from Sutherland, during the period 1985-88. Analysis of the photometry and radial velocities derived from the spectroscopy gives a modulation period of 0.06143 d, free from the alias prob…