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The Shape of Soft X-ray Spectra of Quasars

Published online by Cambridge University Press:  07 August 2017

D. A. Schwartz ,
Y. Qian  and
W. H. Tucker
D. A. Schwartz
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA
Y. Qian
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA
W. H. Tucker
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA

Extract

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Several lines of evidence suggest that the x-ray spectra of quasars are not simple, exact power laws: 1. when Wilkes and Elvis (1987) analyzed quasars as power laws they found an absorption less than that due to our galaxy; 2. The mean 0.3 to 3.5 keV spectral index is steeper than the mean for the 2 to 20 keV range; 3. although several lines of evidence argue that AGN provide a significant portion (perhaps all) of the x-ray background, the diffuse background spectrum does not agree with the x-ray power-law indices measured for quasars or Seyfert galaxies. Schwartz and Tucker (1988) have suggested that all the above conflicts are reconciled if the slope in the Log(flux density) vs. Log(energy) plot flattens continuously with increasing energy. In this paper we utilize one particular parameterization suggested for the flux density, which we call the “log-slope” model:

where f is the flux density, K a normalization parameter which is not of interest here, and a and b are the two parameters of our fit.

Type
Part 3: X-rays and the Central Source
Information
Symposium - International Astronomical Union , Volume 134: Active Galactic Nuclei , 1989 , pp. 175 - 176
Copyright
Copyright © Kluwer 1989 

References

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