High-energy emission in low-mass microquasars

Abstract

Microquasars are binary systems with a compact object accretingfrom a donor star, characterised by the presence of relativisticjets. The electromagnetic spectra of microquasars can range from radioto gamma-rays. In this work we explore the possibility of obtaining high-energyemission from microquasars where the donor star is a low-mass,old and dim star without strong winds. We propose that the interactionof relativistic particles with radiation and magnetic fields in the jetcan be an efficient channel of gamma-ray production in such systems.We focus particularly in proton-dominated jets. We develop a simplemodel to characterise the jet and the distribution of relativistic particlesin steady state. We then calculate the emission spectrum due to differentprocesses: synchrotron radiation, inverse Compton scattering andproton-photon interaction. The contribution of secondary leptons is alsoestimated. Our results indicate that, under some conditions, low-massmicroquasars might be gamma-ray sources detectable by high-energy instrumentslike GLAST.