Multi-band implications of external-IC flares

TL;DR

This paper investigates the impact of external-IC flares on multi-band emissions in blazars using a time-dependent SSC model, revealing that external radiation fields can explain rapid gamma-ray variability but pose challenges for other bands.

Contribution

It introduces a spatially resolved, time-dependent SSC model including Fermi-I acceleration to analyze orphan gamma-ray flares in Mrk501, highlighting the role of external radiation fields.

Findings

External radiation fields can reproduce high-energy lightcurves.

Inverse Compton cooling constrains model parameters.

Extreme parameter ranges are required to fit all observations.

Abstract

Very fast variability on scales of minutes is regularly observed in Blazars. The assumption that these flares are emerging from the dominant emission zone of the very high energy (VHE) radiation within the jet challenges current acceleration and radiation models. In this work we use a spatially resolved and time dependent synchrotron-self-Compton (SSC) model that includes the full time dependence of Fermi-I acceleration. We use the (apparent) orphan $\gamma$-ray flare of \textit{Mrk501} during MJD 54952 and test various flare scenarios against the observed data. We find that a rapidly variable external radiation field can reproduce the high energy lightcurve best. However, the effect of the strong inverse Compton (IC) cooling on other bands and the X-ray observations are constraining the parameters to rather extreme ranges. Then again other scenarios would require parameters even more extreme or stronger physical constraints on the rise and decay of the source of the variability which might be in contradiction with constraints derived from the size of the black hole's ergosphere.