Search Publications
Two patterns of correlated X-ray timing and spectral behaviour in low-mass X-ray binaries.
van der Klis, M.; Hasinger, G.
Exosat data are used to study the power spectra of 16 LMXBs as a function of their behavior in X-ray color-color diagrams. The study confirms the existence of a class of sources with three-branched Z-shaped colour-colour diagrams characterized by a temporal behavior that is strongly dependent on the position of the source on the Z. Evidence for an…
Accretion-powered X-ray pulsars.
Nagase, Fumiaki
This paper gives an overview of X-ray pulsars powered by the accretion of matter from a companion star in a close binary system. Recent advances in studies of X-ray pulsars are reviewed, with a special focus on the results of observations by the Hakucho and Tenma satellites. Some topics revealed by the Ginga satellite in the last one-and-a-half ye…
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…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. I. The Discovery and the Luminosity Dependence of the Pulse Period Variations
Stella, L.; Parmar, A. N.; White, N. E. +2 more
The discovery of a new transient X-ray pulsar, EXO 2030+375, that is associated with a Be star companion, is reported. The results of a series of EXOSAT observations, where the evolution of the pulsar's properties over two orders of magnitude in luminosity was monitored. The dependence of the change in pulsar period on luminosity is measured and c…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. II. The Luminosity Dependence of the Pulse Profile
Stella, L.; Parmar, A. N.; White, N. E.
During an outburst from the transient, 42 s, X-ray pulsar EXO 2030+375, marked luminosity-dependent changes in pulsar profile were observed. At high luminosities the pulse profile consisted of a smooth asymmetric main pulse separated by about 180 deg in phase from a small interpulse. As the luminosity decreased by a factor of about 100, the relati…
Spectral classification of low-mass X-ray binary (LMXB) energy spectra with color-color diagrams.
Hasinger, G.; Truemper, J.; Schulz, N. S.
In this article we describe spectral variations of a large sample of low-mass X-ray binaries (LMXBs). The observations are done with the European X-ray Observatory EXOSAT. We decomposed the measured X-ray spectrum into three energy bands and plotted them into color-color and hardness-intensity diagrams. Correlations are compared with a few templat…
The X-ray flare and the quiescent emission from Algol as detected by EXOSAT.
Mewe, R.; van den Oord, G. H. J.
The Algol system was observed on August 18/19,1983 with different combinations of three instruments aboard EXOSAT: the low-energy channel multiplier array, the medium-energy proportional counters, and the transmission grating spectrometer. The X-ray flare observed on August 19 was analyzed and the decay phase was studied. It is shown that during t…
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…
Coronal Activity in F-, G-, and K-Type Stars. III. The Coronal Differential Emission Measure Distribution of Capella, sigma 2 Coronae Borealis, and Procyon
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
EXOSAT soft X-ray spectra of three binary systems of cool stars are analyzed: Capella (G6 III + F9 III), Sigma-squared CrB (F8 V + G1 V), and Procyon (F5 IV-V + DF). The EXOSAT transmission grating spectrometer permits the study of individual spectral lines and line complexes between 10 and 200 A with approximately 3 A resolution. First it is demo…
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…