A broadband leptonic model for gamma-ray emitting microquasars
Abstract
Observational and theoretical studies point to microquasars (MQs) as possible counterparts of a significant fraction of the unidentified gamma-ray sources detected so far. At present, it is not well known what is the proper scenario for explaining the emission beyond soft X-rays from these objects, nor what is the precise connection between the radio and the high-energy radiation. We develop a new model where the MQ jet is dynamically dominated by cold protons and radiatively dominated by relativistic leptons. The matter content and power of the jet are both related with the accretion process. The magnetic field is assumed to be close to equipartition, although it is attached to and dominated by the jet matter. Concerning the relativistic particles in the jet, their maximum energy depends on both the acceleration efficiency and the energy losses. The model takes into account the interaction of the relativistic jet particles with the magnetic field, and all the photon and matter fields. Such interaction produces significant amounts of radiation from radio to very high energies through synchrotron, relativistic Bremsstrahlung, and inverse Compton (IC) processes. Variability of the emission, produced by changes in the accretion process (e.g. via orbital eccentricity), is also expected. The effects of the gamma-ray absorption by the external photon fields on the gamma-ray spectrum have been taken into account, revealing clear spectral features that might be observed. This model is consistent with the accretion scenario, the energy conservation laws, and the present observational knowledge, and can provide deeper physical information of the source when tested against multiwavelength data.Keywords
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