A microquasar model applied to unidentified gamma-ray sources

Abstract

Among unidentified gamma-ray sources in the galactic plane, there are some that present significant variability and have been proposed to be high-mass microquasars. To deepen the study of the possible association between variable low galactic latitude gamma-ray sources and microquasars, we have applied a leptonic jet model based on the microquasar scenario that reproduces the gamma-ray spectrum of three unidentified gamma-ray sources, 3EG J1735−1500, 3EG J1828+0142 and GRO J1411−64, and is consistent with the observational constraints at lower energies. We conclude that if these sources were generated by microquasars, the particle acceleration processes could not be as efficient as in other objects of this type that present harder gamma-ray spectra. Moreover, the dominant mechanism of high-energy emission should be synchrotron self-Compton (SSC) scattering, and the radio jets may only be observed at low frequencies. For each particular case, further predictions of jet physical conditions and variability generation mechanisms have been made in the context of the model. Although there might be other candidates able to explain the emission coming from these sources, microquasars cannot be excluded as counterparts. Observations performed by the next generation of gamma-ray instruments, like GLAST, are required to test the proposed model.

Radio detections towards unidentified variable EGRET sources

“…Bosch-Ramon et al (2006a) applied a microquasar model to explain the high-energy γ-ray emission of 3EG J1735−1500 consistent with the observations at lower energies (from radio frequencies to soft γ-rays) within the EGRET error box. Although their theoretical model suggests that a microquasar Var.…”

pγ interactions in Galactic jets as a plausible origin of the positron excess

“…Low mass microquasars are of special interest in this regard, for hadronic models based on inelastic pp collisions are not expected to play a leading role, the companion star being cold and old. Because of the same reasons, the external photon background are scarce, what would limit (albeit not rule out in all cases, especially due to self-synchrotron Compton, see, e.g., Bosch-Ramon et al 2006a,2006b) the ability of leptonic processes to dominate the spectra. If jets accelerate protons, these sources may lead to multi-particle injection via pγ processes, where perhaps the photons are synchrotron generated at the base of the jets, see e.g., Levinson & Waxman 2001.…”

INTEGRAL and XMM-Newton observations towards the unidentified MeV source GRO J1411-64

“…We have applied to the non-simultaneous data from XMM-Newton (treating them as an upper limit 1 ), INTEGRAL and COMPTEL the microquasar model presented by Bosch-Ramon et al (2006). This model consists of a magnetized conical jet filled with relativistic electrons which radiate through synchrotron and inverse Compton scattering with star, disk, corona and synchrotron photons.…”

“…These electrons lose energy mainly through adiabatical losses, as a first order approximation. At the top of Table 5, parameter values for a typical microquasar system and jet geometry are given (Bosch-Ramon et al 2006). We have considered different values within the range open for the free parameters finding that it is not possible to obtain a simple microquasar model that could fit the SED.…”