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Redshift evolution of X-ray spectral index of quasars observed by XMM-NEWTON/SDSS

Misra, R.; Hayman, Z. M.; Shehata, SH. M. +2 more

We study the X-ray spectral evolution of quasars with red-shift using a sample of 1280 quasars constructed by cross-referencing the XMM-Newton 3 XMM - DR 7 and the optical SDSS-DR14 catalogues. The sources were selected to have a minimum detected X-ray counts >600 and which were not affected by high background. The sample redshift distribution …