A new ordering parameter of spectral energy distributions from synchrotron self-Compton emitting blazars

Abstract

The broad‐band SEDs of blazars exhibit two broad spectral components, which in leptonic emission models are attributed to synchrotron radiation and synchrotron self‐Compton (SSC) radiation of relativistic electrons. During high‐state phases, the high‐frequency SSC component often dominates the low‐frequency synchrotron component, implying that the inverse‐Compton SSC losses of electrons are at least equal to or greater than the synchrotron losses of electrons. We calculate from the analytical solution of the kinetic equation of relativistic electrons, subject to the combined linear synchrotron and non‐linear SSC cooling, for monoenergetic injection the time‐integrated total synchrotron and SSC radiation fluences and spectral energy distributions (SEDs). Depending on the ratio of the initial cooling terms, displayed by the injection parameter α, we find for α≪ 1, implying complete linear cooling, that the synchrotron peak dominates the inverse‐Compton peak and the usual results of the spectra are recovered. For α≫ 1, the SSC peak dominates the synchrotron peak, proving our assumption that in such a case the cooling becomes initially non‐linear. The spectra also show some unique features, which can be attributed directly to the non‐linear cooling. To show the potential of the model, we apply it to outbursts of 3C 279 and 3C 454.3, successfully reproducing the SEDs. The results of our analysis are promising, and we argue that this non‐equilibrium model should be considered in future modelling attempts for blazar flares.

Modelling of blazar SEDs with the nonlinear SSC cooling process

“…We first presented the results of Zacharias & Schlickeiser (2012a), in which we calculated the SED including the synchrotron and the SSC component. Then we proceeded with the recent work of Zacharias & Schlickeiser (2012b), where we added the effect of external Compton cooling, yielding a third broad component in the SED.…”

First-generation science cases for ground-based terahertz telescopes

“…The peak of the lower-energy bump between 10 13 and 10 17 Hz is due to the synchrotron emission; moving relativistic shocks in the jet ("shock-in-jet" model) are generally considered for non-thermal particle acceleration (Blandford & Königl 1979;Marscher 1980). On the other hand, a high energy bump between 10 21 and 10 24 Hz is due to SSC and/or EC as mentioned above (Abdo et al 2011), although which of EC and SSC is the dominant mechanism of the high-energy component is not yet conclusive (Ghisellini, Celotti, & Costamante 2002;Sikora et al 2009;Zacharias & Schlickeiser 2012). …”

Nonlinear synchrotron self-compton modelling of blazars

“…This injection corresponds to a complete flaring event and does not represent the steady state. A complete description of combined linear synchrotron and nonlinear SSC modelling is constructed by M. Zacharias and R. Schlickeiser [9] and reveals that SSC loss rate of the electron depends on the energy integral of the actual electron spectrum n( ,t), where is particle energy and t is time, suggesting that SSC cooling term is nonlinear and time dependent. This dependence of cooling rate on the energy integral is a collective effect which is completely different from linear synchrotron loss rate of the electron.…”

“…The nonlinear SSC model presented by [9] solved the kinetic equation of electron for the total radiative losses (including synchrotron and SSC losses) to get a dimensionless ordering parameter, , as given by:…”

“…ssc and . s are SSC and synchrotron cooling rates respectively, 0 is electron Lorentz factor, Q 0 is injection electron density while A 0 and D 0 are constants appearing is these loss terms as given in [9].…”