Studying the influence of external photon fields on blazar spectra using a one-zone hadro-leptonic time-dependent model

TL;DR

This paper investigates how external photon fields influence blazar spectra by using a new time-dependent one-zone hadro-leptonic model, revealing that these fields can significantly alter the typical spectral features and affect jet emission dynamics.

Contribution

It introduces a novel time-dependent model (OneHaLe) to study the impact of external thermal photon fields on blazar spectra, including steady-state and moving emission regions.

Findings

External photon fields can disrupt the typical double-humped blazar spectrum.

Moving emission regions can traverse the jet without reaching steady states.

External fields significantly influence proton-photon interactions and resulting spectra.

Abstract

The recent associations of neutrinos with blazars require the efficient interaction of relativistic protons with ambient soft photon fields. However, along side the neutrinos gamma-ray photons are produced which interact with the same soft photon fields producing electron-positron pairs. The strength of this cascade has significant consequences on the photon spectrum in various energy bands and puts severe constraints on the pion and neutrino production. In this study, we discuss the influence of the external thermal photon fields (accretion disk, broad-line region, and dusty torus) on the proton-photon interactions employing a newly developed time-dependent one-zone hadro-leptonic code (OneHaLe). We present steady-state cases, as well as a time-dependent case, where the emission region moves through the jet. Within the limits of this toy study, the external fields can disrupt the ``usual'' double-humped blazar spectrum. Similarly, a moving region would cross significant portions of the jet without reaching the previously-found steady states.