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astro-ph2005
On the Exotic Hard X-ray Source Populations in the Hellas2XMM survey
C. Vignali, M. Mignoli
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 characteri…
astro-ph2004
Type II quasar candidates in the Sloan Digital Sky Survey: evidence for X-ray obscuration
C. Vignali, D. M. Alexander, A. Comastri
Recent X-ray surveys with Chandra and XMM-Newton have found several genuine Type II quasars, the long sought-after population of high-luminosity (high-redshift) Seyfert 2 galaxies,…
astro-ph2004
The HELLAS2XMM 1dF Survey: a window on exotic hard X-ray selected sources
C. Vignali
Recent Chandra and XMM-Newton surveys have confirmed that the cosmic X-ray background is mostly due to accretion onto super-massive black holes, integrated over cosmic time. Here w…