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

TL;DR

This paper introduces a new parameter to describe the spectral energy distributions of blazars, accounting for nonlinear cooling effects, and demonstrates its application to real blazar outbursts, improving modeling accuracy.

Contribution

It develops an analytical model incorporating nonlinear synchrotron self-Compton cooling and applies it to blazar SEDs, highlighting the importance of the injection parameter in spectral dominance.

Findings

For small alpha, spectra match linear cooling results.

For large alpha, SSC dominates synchrotron emission.

Model successfully reproduces observed blazar SEDs.

Abstract

The broadband 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 nonlinear synchrotron self-Compton cooling, for monoenergetic injection the time-integrated total synchrotron and SSC radiation fluences and spectral energy distributions (SED). Depending on the ratio of the initial cooling terms, displayed by the injection parameter $\alpha$, we find for $\alpha\ll 1$, implying complete linear cooling, that the synchrotron peak dominates the inverse Compton peak and the usual results of the spectra are recovered. For $\alpha\gg 1$ 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 modeling attempts for blazar flares.