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We analyze the 2.5--10 keV X-ray spectra of the luminous quasar 3C 273 andsimultaneous observations in UV wavelengths from XMM--Newton between 2000 and2015. The lowest flux level ever was observed in 2015. The continuum emissionfrom 3C 273 is generally best described by an absorbed power-law but duringextremely low states the addition of fluorescence from the K-shell iron lineimproves the fit. We study the spectral evolution of the source during itsextended quiescent state and also examine connections between the X-ray andultraviolet emissions, which have been seen in some, but not all, previouswork. We detect a possible anti-correlation between these two bands during thelow state that characterized 3C 273 for most of this period; however, this wasnot present during a flaring state. A harder-when-brighter trend for the X-rayspectrum was observed in these long-term observations of 3C 273 for the firsttime. We suggest that the X-ray emission in 3C 273 is the result of inverseCompton scattering of soft UV seed photons (emitted from the local environmentof the AGN), most likely in a thermal corona. We can explain the significanttemporal variation of the spectral continuum as an outcome of changing opticaldepth of the comptonizing medium, along the lines of the wind-shock modelproposed by Courvoisier and Camenzind (1989).

Origin of X-rays in the low state of the FSRQ 3C 273: Evidence of inverse Compton emission