Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992apj...384...62c&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 384, Jan. 1, 1992, p. 62-71. Research supported by Harvard-Smithsonian Cent
Astronomy and Astrophysics
Astrophysics
88
Exosat Satellite, Quasars, X Ray Spectra, Galactic Nuclei, Seyfert Galaxies
Scientific paper
Measurements of the X-ray spectra in the 0.1-10-keV energy range for 17 AGN (mostly PG quasars) using the Exosat Low and Medium Energy arrays are presented. For each object, the best-fit spectral parameters in the medium-energy range (about 2-10 keV), i.e., the power-law slope, the normalization, and the absorbing column density, are determined. In this energy range, all the spectra are well described by a single power law model, with a wide distribution of energy spectral indices in the range 0.4-1.3. The average spectral index is 0.89 +/-0.06, but most of the objects are distributed around 1.0. Inclusion of lower energy data (about 0.1-2.0 keV) shows the presence of significant soft excess in six out of 17 cases. This soft excess emission can be modeled by either a steep power law with the average spectral index ranging from 2.7 to 4.2 or the high-energy tail of a blackbody with temperatures in the range 40-80 eV.
Comastri Andrea
Elvis Martin
Giommi Paolo
McDowell Jonathan C.
Setti Giancarlo
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