Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983chjss...3q.146z&link_type=abstract
(Chinese Journal of Space Science, vol. 3, no. 2, 1983, p. 146-156) Chinese Astronomy and Astrophysics (ISSN 0275-1062), vol. 7,
Astronomy and Astrophysics
Astronomy
Galactic Nuclei, Quasars, Seyfert Galaxies, X Ray Sources, Active Galactic Nuclei, Active Galaxies, Black Holes (Astronomy), Luminosity, Red Shift, Statistical Analysis, Stellar Mass Accretion
Scientific paper
The evolution of X-ray radiation of 273 objects (235 quasars and 38 type I Seyferts) in the 0.5-4.5 keV band is investigated. The Lx-z plot of these objects shows a natural physical sequence (the QE band) which connects the active galaxies, such as quasars and Seyferts, with respect to the energy and mass of the central compact object. It is determined that quasars may quickly cross the lower envelope of the QE band and disappear, based on the spherically symmetric accretion model by a massive black hole. High-redshift quasars are found to have comparatively short (approximately 10 to the 6th yr) staying times on this QE band, whereas low-redshift quasars and type I Seyferts have longer (approximately 10 to the 8th yr) staying times. These results suggest that active galactic nuclei such as quasars and Seyferts may be manifestations of galactic nuclei in an excited state under specific conditions. It is found that two evolutionary stages exist in the optical luminosities of quasars: the optically bright and optically faint stages. The parameters characterizing the typical properties of quasars are found to be distinctive in each of these stages, which indicates that the radiation mechanisms in different energy regions are different.
Liu Rong-Li
Yang Hyun Seok
Zhang Qing-Hong
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