Optical and X-ray Variability of Blazars
  Here we report our recent results of variability studies in optical and X-ray
bands of three blazars namely 3C 273, PKS 2155 - 304 and BL Lacertae with
XMM-Newton. We found large amplitude optical to X-rays variability in 3C 273,
and PKS 2155 - 304 on year time scale. In 3C 273, we noticed that synchrotron
cooling and particle acceleration are at work at different epoch of
observations. In PKS 2155 - 304, spectral energy distribution from optical to
X-ray is fitted with LPPL (log parabolic + power law) model. In BL Lacertae,
optical flux and degree of polarization were anti-correlated.
