Spectral variability of blazars
Broadband spectral characteristics of different subclasses of
g-ray blazars in different g-ray intensity states
are presented, contrasted and discussed in the framework of
currently popular leptonic jet models. Recent modeling results
on all available simultaneous broadband spectra of the flat-spectrum
radio quasar (FSRQ) PKS 0528+134 during 6 years of EGRET observations
and on a sequence of simultaneous broadband spectra of the
high-frequency peaked BL Lac object (HBL) Mrk 501 during 6
months in 1997 are discussed. These and other modeling results
confirm that HBLs may be fitted successfully with pure SSC models,
while FSRQs require a strong component due to external
inverse-Compton scattering. Flaring properties of HBLs can
be understood in terms of a hardening of the electron spectra
in the jet, while g-ray flares of quasars appear to be
more closely related to an intensification of the external soft
photon field, possibly caused by an increasing bulk Lorentz
factor. A surprising prediction of this interpretation is that
the peak of the synchrotron spectrum of FSRQs is expected to
shift towards lower frequencies during flares, while it is
known to shift towards higher energies during flares of HBLs.
File translated from TEX by TTH, version 2.32.
On 16 Jul 1999, 09:18.