2008 Supplement: Frascati Workshop 2007 / Pian

INTEGRAL and Swift Observations of Blazars in Outburst

E. Pian, L. Foschini, G. Ghisellini


The blazars 3C 454.3, PKS 0537-441 and PKS 2155-304 are traditionally
known to be among the most active sources of this class. They emit at
all frequencies, up to gamma-rays, and are good probes of
multiwavelength nuclear variability. The first two also have luminous
broad emission line regions. We have recently monitored them with
various facilities, including Swift and INTEGRAL, and have interpreted
their variations with models of non-thermal radiation from a
relativistic jet. In particular, we have tested for the first two
sources the hypothesis that the variability is produced within the jet
through internal shocks, i.e. collisions of relativistic plasma blobs.
This allows a parameterization of all physical quantities as functions
of the bulk Lorentz factor. We have made the critical assumption that
every flaring episode is characterized by a fixed amount of energy. The
model reproduces satisfactorily the multiwavelength data, and
especially the gamma-ray spectra, when available. The model is not
applicable to PKS 2155-304, the variability of which is caused by
independent variations of a few individual parameters.


galaxies: active

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