The soft X-ray spectra of active galactic nuclei

  • G. Branduardi-Raymont
Spectral Formation
Part of the Lecture Notes in Physics book series (LNP, volume 266)


EXOSAT LE and ME data on Seyfert 1 galaxies and quasars are reviewed: the observations indicate that a strong flux of soft X-rays, in excess of the power-law continuum that extends over most of the spectrum, is a common feature of the emission of Active Galactic Nuclei (AGN). This excess is seen in both Seyfert galaxies and quasars, irrespective of whether they are X-ray or optically selected. EXOSAT observations reveal that this low-energy X-ray spectral component, which is often identified with the emission of an optically thick accretion disc surrounding a central massive black hole, is highly variable, with changes in flux by more than a factor of ten over a few months. This new result and the observation of spectral variability correlated with the changes in flux give clues to the mechanisms of X-ray production in AGN and to the structure of the innermost parts of the accretion disc in these objects.


Accretion Disc Energy Index Seyfert Galaxy Strong Flux Thick Accretion Disc 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • G. Branduardi-Raymont
    • 1
  1. 1.Mullard Space Science LaboratoryUniversity College LondonDorkingUK

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