Search Publications
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…
Evaluation of cometary dust parameters from numerical simulations: comparison with an analytical approach and the role of anisotropic emissions.
Fulle, M.
A numerical method is developed which models cometary dust tails by means of sample grains. The orbital motion of the grains is rigorously computed, avoiding any Finson-Probstein hypersonic condition and dust shell geometry approximation. The model is applied to the dust tails of Comet Seki-Lines 1962III and Comet Kohoutek 1973XII. The results sho…
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 Ultraviolet Spectrum of eta Carinae
Cassatella, Angelo; Viotti, Roberto; Rossi, Lucio +2 more
An atlas of the high-resolution UV spectrum of Eta Car from 1200 to 1974 A and from 2200 to 3230 A is presented, based on IUE observations made between 1978 and 1980. The fluxes and equivalent widths of the emission and absorption features, and the stellar continuum in line-free regions are presented. The profiles displayed by the most intense emi…
A Soft X-Ray Survey of Hot White Dwarfs with EXOSAT
Heise, J.; Paerels, F. B. S.
Broadband multicolor soft X-ray photometry of 34 hot white dwarfs is presented, obtained with the Low Energy Imaging Telescopes on Exosat. By combining the soft X-ray fluxes with measurements of the stellar parameters in the UV and optical bands, photospheric He abundances for 16 of the 21 hot DA white dwarfs are derived. Supplemented by five star…
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 velocity distributions of cometary protons picked up by the solar wind
Balsiger, H.; Neubauer, F. M.; Fuselier, S. A. +3 more
Velocity space distributions of picked up cometary protons were measured by the ion mass spectrometer on the Giotto spacecraft upstream of the Halley bow shock. Large pitch angle anisotropies were observed at all distances >1.2×106 km from the comet. As expected, pitch angle diffusion was much more rapid than energy diffusion. When t…
Emission-Line Variability of Fairall 9: Determination of the Size of the Broad-Line Region and the Direction of Gas Motion
Koratkar, Anuradha P.; Gaskell, C. Martin
A cross-correlation analysis has been performed on 118 IUE spectra of Fairall 9 available from 1978 to January 1987 to determine the size of the broad-line region and the average direction of gas motion. Analysis of the line flux shows that the C IV λ1549 emitting region is 124 +/- 39 light days from the central source and the Mg II λ2800 emitting…
Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. XI. Ultraviolet spectral images of AR Lacertae in September 1985.
Linsky, J. L.; Walter, F. M.; Neff, J. E. +1 more
High-resolution IUE SWP and LWP spectra of the bright eclipsing RS CVn system AR Lac, obtained during 40 h of continuous observations on September 18-19, 1985, are compiled and used to derive chromosphere images. The data and results are presented graphically and discussed in detail. The K 0 IV star is found to have a globally brighter trailing he…