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تسجيل مستخدم جديدRemarkable Spectral Variability of PDS 456
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We report on the highest to date signal-to-noise-ratio X-ray spectrum of the luminous quasar PDS 456, as obtained during two XMM-Newton orbits in September 2007. The present spectrum is considerably different from several previous X-ray spectra recorded for PDS 456 since 1998. The ultra-high-velocity outflow seen as recently as February 2007 is not detected in absorption. Conversely, a significant reflection component is detected. The reflection model suggests the reflecting medium may be outflowing at a velocity v/c = -0.06 +/- 0.02. The present spectrum is analyzed in the context of the previous ones in an attempt to understand all spectra within the framework of a single model. We examine whether an outflow with variable partial covering of the X-ray source along the line of sight that also reflects the source from other lines of sight can explain the dramatic variations in the broad-band spectral curvature of PDS 456. It is established that absorption plays a major role in shaping the spectrum of other epochs, while the 2007 XMM-Newton spectrum is dominated by reflection, and the coverage of the source by the putative outflow is small (< 20%).
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We present a detailed analysis of a recent $500$ ks net exposure textit{Suzaku} observation, carried out in 2013, of the nearby ($z=0.184$) luminous (L$_{rm bol}sim10^{47}$ erg s$^{-1}$) quasar PDS 456 in which the X-ray flux was unusually low. The s
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