The X-ray spectrum of QSO 1821 + 643

Details The X-ray spectrum of QSO 1821 + 643 The X-ray spectrum of QSO 1821 + 643

Jun 1989

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989mnras.238..917w&link_type=abstract

Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711), vol. 238, June 1, 1989, p. 917-924. Research supported by SE

Astronomy and Astrophysics

Astronomy

25

Accretion Disks, Quasars, X Ray Spectra, Active Galaxies, Exosat Satellite, Heao 1

Scientific paper

Pravdo and Marshall (1984) have reported an unusually soft X-ray spectrum for the high-luminosity QSO 1821 + 643, based on measurements from the A2 experiment on HEAO-1. However, in a series of Exosat observations of this object, the medium-energy X-ray spectrum is found to be consistent with the canonical form observed in low-luminosity active galaxies. The most plausible interpretation is that two continuum components are present, a soft component which declined by a factor of about 10 over the period 1977-85 and a medium-energy component of standard slope which showed only a factor of about 2 decrease over the same period. This source may provide an important test of the hypothesis that the soft excesses present in the X-ray spectra of many active galaxies originate in the hot innermost regions of an accretion disk.

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