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
disagree with this trend as the variability amplitude decreases from soft to hard X-ray bands. On
intra-day time-scales 3C 273 showed small amplitude variability in X-ray bands. A hardness
ratio analysis in the X-ray regime indicates that the particle acceleration mechanism dominates
the cooling mechanism during most of the ∼12 yr span of these observations
