Multiband variability in the blazar 3C 273 with XMM–Newton

Abstract

We have undertaken a nearly simultaneous optical/UV and X-ray variability study of the flat spectrum radio quasar, 3C 273 using data available from the XMM–Newton satellite mission from 2000 June to 2012 July. Here, we focus on the multiwavelength flux variability on both intra-day and long time-scales of this very well known radio-loud source. We found high flux variability over long time-scales in all bands for which observations were made. The optical/UV variability amplitude was more than twice than that in the X-ray bands. There is some frequency dependence of the variability in optical/UV bands in the sense that the variability amplitude increases with increasing frequency; however, the X-ray emissions disagreewiththistrendasthevariabilityamplitudedecreasesfromsofttohardX-raybands.On intra-day time-scales 3C 273 showed small amplitude variability in X-ray bands. A hardness ratio analysis in the X-rayregime indicates that theparticle acceleration mechanism dominates the cooling mechanism during most of the ∼12 yr span of these observations.