content 16-July-2019 14:53:41

Science Results

Currently, there have been more than 1000 publications of EXOSAT data in leading scientific journals. These include many notable discoveries:

  • The detection of quasi-periodic oscillations (QPO) in the radiation from GX 5-1. These pronounced oscillations are now known to be common in low-mass X-ray binaries. In a given source, the frequency behaviour of the QPO varies with luminosity and spectral hardness in a highly characteristic manner which depends upon the instantaneous position of the source on an X-ray colour-intensity plot. The systematic nature of these correlations makes this an important tool for studying accretion processes in these enigmatic systems which generally do not exhibit neutron-star spin periods

  • Observations of the pulsing X-ray nova EXO 2030+375 revealed for the first time in a single system, the changes in pulse period and shape as the luminosity changed by factor 100. These observations provided new insights into the accretion dynamics and beaming of accreting neutron stars

  • The detections of Doppler variations in the Fe-line from SS433, showing the emission to be thermal (with a rest energy of 6.7 keV) and to arise from the near-side jet

  • The discovery of the spectacularly short 11 minute period in the globular cluster X-ray burster XB 1820-30

  • A spectral survey of 48 Seyfert galaxies over two decades of energy (0.1-10 keV) showed many examples with a 'soft' X-ray component which supports an accretion disk model for Active Galactic Nuclei

  • The finding that short-term variability is a common characteristic of Active Galactic Nuclei, and that this variation lacks a characteristic time scale

  • The discovery that there is a lack of luminous (in X-rays) clusters at z>0.1 showing that cluster evolution is strong and continuing


Last Update: 30 June 2003

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