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X-ray properties of the quasar HE0450-2958
Xin-Lin Zhou, Fang Yang, Xiao-Rong Lv +1
We present an {\it XMM-Newton} EPIC observation of HE0450-2958 which may be a ``naked''quasar as suggested by Magain et al. The \xmm EPIC spectra show a substantial soft X-ray exce…
Cosmological Evolution of the Duty Cycle of Quasars
Jian-Min Wang, Yan-Mei Chen, Fan Zhang
Quasars are powered by accretion onto supermassive black holes, but the problem of the duty cycle related to the episodic activity of the black holes remains open as one of the maj…
The Unified Model of Active Galactic Nuclei: I. Non-hidden Broad Line Region Seyfert 2 and Narrow Line Seyfert 1 Galaxies
E. -P Zhang, J. -M. Wang
The unified model of Seyfert galaxies suggests that there are hidden broad-line regions (HBLRs) in Seyfert 2 galaxies (S2s). However, there is increasing evidence for the appearanc…
Evidence for Rapidly Spinning Black Holes in Quasars
Jian-Min Wang, Yan-Mei Chen, Luis C. Ho +1
It has long been believed that accretion onto supermassive black holes powers quasars, but there has been relatively few observational constraints on the spins of the black holes.…