ISDC Data Centre for Astrophysics

Multiple synchrotron self-Compton modeling of gamma-ray flares in 3C 279

We test and constrain a new theoretical model for the high-energy emission of blazars. We fit the model parameters to longterm lightcurves and to radio-to-gamma-ray spectra of 3C 279. It turns out that the modeling of shock waves in a jet emitting synchrotron self-Compton radiation including multiple-order scatterings is a promising alternative to the usual external-Compton emission models.

Türler & Björnsson 2011, arXiv:1109.2518

ABSTRACT

The correlation often observed in blazars between optical-to-radio outbursts and gamma-ray flares suggests that the high-energy emission region shall be co-spatial with the radio knots, several parsecs away from the central engine. This would prevent the important contribution at high-energies from the Compton scattering of seed photons from the accretion disk and the broad-line region that is generally used to model the spectral energy distribution of low-frequency peaking blazars. While a pure synchrotron self-Compton model has so far failed to explain the observed gamma-ray emission of a flat spectrum radio quasar like 3C 279, the inclusion of the effect of multiple inverse-Compton scattering might solve the apparent paradox. Here, we present for the first time a physical, self-consistent SSC modeling of a series of shock-waves in the jet of 3C 279. We show that the analytic description of the high-energy emission from multiple inverse-Compton scatterings in the Klein-Nishina limit can fairly well account for the observed gamma-ray spectrum of 3C 279 in flaring states.

Multiple SSC modeling of 19 years of flaring in the blazar 3C 279
Animation of the modeled evolution of the spectral energy distribution of 3C 279 (grey line). The variability is assumed to be due to the emission of a succession of self-similar shock waves (colored lines) in the relativistic jet of the blazar. Synchrotron emission and associated multiple inverse-Compton scattering account for the low- and high-frequency bumps, respectively. Observed data points from Hartman et al. (2001) and from MAGIC (Aleksíc et al. 2011 A&A 530, A4) are shown for comparison.
Credits: M. Türler (ISDC)

Fit of a series of synchrotron outbursts to optical-to-radio lightcurves of 3C 279
Fit of ten lightcurves of 3C 279 in the optical-to-radio domain with a series of self-similar synchrotron model outbursts. The contribution of individual outbursts is shown with different colors.
Credits: M. Türler (ISDC)

Spectral evolution of the average synchrotron outburst in 3C 279
The evolution with time of the average synchrotron outburst in 3C 279 as derived from the fit of 19 lightcurves (see Fig. 2, above). The grey lines show spectra at different times after the onset of an outburst. The point of maximum flux follows the red line. The evolution peak of all individual outbursts is shown by colored dots.
Credits: M. Türler (ISDC)

Model decomposition of the spectral energy distribution of 3C 279 in early 1996
Spectral decomposition of the observations of 3C 279 in period P5a (Hartman et al. 2001) derived by a combined fit of all available spectra and lightcurves. The emission of different model outbursts — corresponding to a succession of different shock waves in the jet — are shown with the same colors as in Figs 2 and 3 (above).
Credits: M. Türler (ISDC)