4,226 research outputs found
On the Exotic Hard X-ray Source Populations in the Hellas2XMM survey
Recent hard X-ray surveys have proven to be effective in discovering large
numbers of X-ray sources that, despite the likely association with active
nuclei, appear to be characterized by "peculiar" properties. Among these
"exotic" source populations, we will focus on the nature of two classes of hard
X-ray sources: those characterized by high X-ray-to-optical flux ratios -- a
fraction of these are associated with the rather elusive Type 2 quasars -- and
the X-ray bright optically normal galaxies, also known as XBONGs.Comment: On behalf of the HELLAS2XMM Collaboration, 6 pages, 4 figures,
contribution to the Proceedings of the COSPAR Scientific Assembly, E1.3
"High-Energy Radiation from Black Holes: from Supermassive Black Holes to
Galactic Solar Mass Black Holes", Paris (France), July 18-25, 2004, accepted
for publication in Advances in Space Researc
Restless Quasar Activity: From BeppoSAX to Chandra and XMM-Newton
We briefly review some of the progress made in the last decade in the study
of the X-ray properties of the quasar population from the luminous, local
objects observed by BeppoSAX to the large, rapidly increasing population of z>4
quasars detected by Chandra and XMM-Newton in recent years.Comment: 4 pages, 4 figures. To appear in the Proceedings of the Symposium
"The Restless High-Energy Universe", 5-8 May 2003, Amsterdam, The
Netherlands, E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers
Ed
The z>4 Quasar Population Observed by Chandra and XMM-Newton
The current status of our Chandra and XMM-Newton project on high-redshift
(z>4) quasars is briefly reviewed. We report the main results obtained in the
last few years for the detected quasars, along with a few (~10%) intriguing
cases where no detection has been obtained with Chandra snapshot observations.Comment: 4 pages, to appear in the proceedings of 'Multiwavelength AGN
surveys' (Cozumel, December 8-12 2003), ed. R. Maiolino and R. Mujic
Compton-thick AGN and the Synthesis of the Cosmic X-ray Background: the Suzaku Perspective
We discuss the abundance of Compton-thick AGN as estimated by the most recent
population synthesis models of the cosmic X-ray background. Only a small
fraction of these elusive objects have been detected so far, in line with the
model expectations. The advances expected by the broad band detectors on board
Suzaku are briefly reviewed.Comment: proceedings of "The Extreme Universe in the Suzaku Era", Kyoto 4-8
December 2006, to be published in Progress of Theoretical Physics, Supplemen
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