On the evolution of the particle distribution and the cascade in a moving, expanding emission region in blazar jets

TL;DR

This paper models how a moving, expanding emission region in blazar jets influences flare profiles, emphasizing gamma-gamma pair production effects, and demonstrates the importance of multiwavelength observations for understanding flare mechanisms.

Contribution

It introduces a semi-analytical model and realistic simulations to study particle evolution and flare profiles in expanding blazar emission regions, highlighting pair production effects.

Findings

Pair production significantly affects flare evolution.

Expansion and opening angle prolong flares.

Flares produce wavelength-dependent light curves with delays.

Abstract

There is a large variety in the models explaining blazar flares. Here, we study the flare profile induced by a moving and expanding blob with special emphasize on the gamma-gamma pair production. We first develop a simple semi-analytical model to study the evolution of the particle distribution in the expanding blob and show the influence of the pair production. In a second step, we produce a realistic simulation using the OneHaLe code based upon parameters of PKS 1510-089. The semi-analytical model shows that the pair production significantly influences the flare evolution, while the opening angle and the expansion can prolong flares considerably. The simulation based on PKS 1510-089 indicate that flares of a moving expanding blob result in strongly wavelength dependant light curves including delayed, secondary flares. A moving, expanding blob can cause significant flaring events with a large variety in light curve profiles. High-cadence multiwavelength observations are necessary to derive the details causing the flare. Extended observations beyond the initial burst may provide important information on the opening angle and the particle content due to delayed secondary flares in some energy bands.