The proton low-mass microquasar: high-energy emission

TL;DR

This paper models high-energy gamma-ray emission from low-mass microquasars, suggesting they could explain halo gamma-ray sources through proton synchrotron radiation and photopion processes, with testable predictions for current telescopes.

Contribution

It introduces a proton microquasar model for gamma-ray emission, exploring its potential to explain halo sources and predicting observable signatures for upcoming gamma-ray and neutrino telescopes.

Findings

Proton synchrotron radiation can produce luminosities up to 10^{37} erg/s in the GLAST energy range.

Models show significant gamma-ray luminosities from low-mass microquasars are feasible.

Predictions include detectable signals for instruments like GLAST, HESS II, MAGIC II, and IceCube.

Abstract

A population of unidentified gamma-ray sources is forming a structure resembling a halo around the Galactic center. These sources are highly variable, and hence they should be associated with compact objects. Microquasars are objects undergoing accretion with relativistic jets; if such an object has a low-mass, evolved, donor star, it might be found in the Galactic halo. If these low-mass microquasars can generate detectable gamma-ray emission, then they are natural candidates to account for the halo high-energy sources. We aim to construct models for high-energy emission of low-mass microquasars, which could produce a significant luminosity in the gamma-ray domain. We consider that a significant fraction of the relativistic particles in the jets of low-mass microquasars are protons and then we study the production of high-energy emission through proton synchrotron radiation and photopion production. Photopair production and leptonic processes are considered as well. We compute a number of specific models with different parameters to explore the possibilities of this scenario.} We find that important luminosities, in the range of $10^{34}-10^{37}$ erg s$^{-1}$, can be achieved by proton synchrotron radiation in the Gamma-Ray Large Area Space Telescope (GLAST) energy range, and lower, but still significant luminosities at higher energies for some models. We conclude that the "proton microquasar" model offers a very interesting alternative to account for the halo gamma-ray sources and presents a variety of predictions that might be tested in the near future by instruments like GLAST, the High-Energy Stereoscopic System II (HESS II), the Major Atmospheric Gamma-ray Imaging Cherenkov telescope II (MAGIC II), and neutrino telescopes like IceCube.