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The flat spectrum radio quasars (FSRQs) are a sub-class of blazarscharacterised by prominent optical emission lines and a collimated large-scalejet along the observer line of sight. An X-ray spectral flattening has beenreported in FSRQs (at relatively high redshifts), attributable to eitherabsorption from gas along the line of sight or intrinsic jet based radiativeprocesses. We study a sample of 16 high redshift FSRQs (z of 1.1 -- 4.7; restframe energy upto 50 keV) observed with XMM-Newton and Swift satellitesspanning 29 epochs. The X-ray spectra are fit with a power law including freeexcess absorption and one multiplied by an exponential roll off to account forthe intrinsic jet based processes. A statistical analysis is used todistinguish between these models to understand the origin of the spectralflattening. The model selection is unable to distinguish between them in ten ofthe sixteen FSRQs. Intrinsic jet based radiative processes are indicated infour FSRQs where we infer energy breaks consistent with their expectation fromthe external Compton scattering of low energy ambient photons. Two of the FSRQsindicate mixed results, supportive of either scenario, illustrating thedifficulty in identifying X-ray absorption signatures. A clear detection can beemployed to disentangle the relative contributions from the inter-galacticmedium and the intra-cluster medium, the methodology of which is outlined andapplied to the latter two sources.

Breaks in the X-ray spectra of high redshift blazars and the intervening medium