Constraining cosmic-ray acceleration in the magnetospheric gaps of Sgr A*

TL;DR

This paper investigates the potential for particle acceleration in Sgr A*'s magnetosphere, suggesting proton acceleration to PeV energies is feasible during its current activity phase, with implications for observed gamma-ray emissions.

Contribution

It provides new constraints on gap-type particle acceleration in Sgr A*, linking accretion activity to cosmic-ray and gamma-ray production capabilities.

Findings

Proton acceleration to PeV energies is possible in current activity phase.

TeV emission can result from electron upscattering, matching observations.

Higher past activity unlikely increased power output unless accretion flow changed.

Abstract

Sagittarius A* (Sgr A*) is a potential VHE gamma-ray and cosmic-ray source. We examine limits to gap-type particle acceleration in the magnetosphere of Sgr A*, showing that in the current phase of activity proton acceleration to PeV energies is possible, with injection powers into the environment usually limited to several 10^{36} erg/s. Compton upscattering of ambient soft photons by gap-accelerated electrons could yield TeV emission compatible with the detected VHE points source. We explore the dependency of the results on changes in the accretion rate showing that higher stages in the past are unlikely to increase the power output unless the inner accretion flows itself changed its configuration.