Swift and XMM-Newton monitoring of the ISP blazar ON 231 in outburst state

We present a detailed temporal and spectral study of the intermediate type blazar, ON 231 with observations taken by Swift and XMM-Newton satellites during an outburst phase in June 2008. The source shows multiple X-ray flares in that period when the flux amplitude varies in the range of 27-38%. The X-ray spectra are well fitted with a broken power-law model indicating the presence of both synchrotron and inverse Compton components. We find that the source shows strong and variable emission in the soft energy bands (below 3-4 keV), where the hard band emission is weak and stable. All the soft X-ray bands show correlated variability with zero lag, while a soft lag of -600 s between the 0.3-0.5 and 4-10 keV bands is observed with DCF analysis. A time-resolved spectral study of the flares gives a positive relation between the total fluxes and the break energies of the two emission components.