Spectral Evolution in Young Active Galactic Nuclei

  • Elihu Boldt
  • Darryl Leiter
Part of the Astrophysics and Space Science Library book series (ASSL, volume 121)


The spectral evolution of AGNs is discussed within the context of a scenario where the cosmic X-ray background (CXB) is dominated by these sources. Attention is drawn to the fact that individually observed AGN X-ray spectra are significantly steeper than that of the CXB. The remarkably flat spectrum thereby required for the “as-yet” unresolved sources of the residual CXB is interpreted as an observational constraint on an earlier stage of AGN evolution. Assuming black hole disk accretion, a picture emerges where young AGNs are compact Eddington limited thermal X-ray sources and where canonical AGNs represent later stages in which they have become appreciably less compact, exhibiting the importance of non-thermal disk-dynamo processes.


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Copyright information

© Springer Science+Business Media Dordrecht 1986

Authors and Affiliations

  • Elihu Boldt
    • 1
  • Darryl Leiter
    • 1
  1. 1.Laboratory for High Energy AstrophysicsNASA/Goddard Space Flight CenterGreenbeltUSA

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