Non-thermal emission from microquasar/ISM interaction

Abstract

Context. The interaction of microquasar jets with their environment can produce non-thermal radiation as in the case of extragalactic outflows impacting on their surroundings. Significant observational evidence of jet/medium interaction in galactic microquasars has been collected in the past few years, although little theoretical work has been done regarding the resulting non-thermal emission. Aims. In this work, we investigate the non-thermal emission produced in the interaction between microquasar jets and their environment, and the physical conditions for its production. Methods. We developed an analytical model based on those successfully applied to extragalactic sources. The jet is taken to be a supersonic and mildly relativistic hydrodynamical outflow. We focus on the jet/shocked medium structure in its adiabatic phase, and assume that it grows in a self-similar way. We calculate the fluxes and spectra of the radiation produced via synchrotron, inverse Compton, and relativistic bremsstrahlung processes by electrons accelerated in strong shocks. A hydrodynamical simulation is also performed to investigate further the jet interaction with the environment and check the physical parameters used in the analytical model. Results. For reasonable values of the magnetic field, and using typical values of the external matter density, the non-thermal particles could produce significant amounts of radiation at different wavelengths, although they do not cool primarily radiatively, but by adiabatic losses. The physical conditions of the analytical jet/medium interaction model are consistent with those found in the hydrodynamical simulation. Conclusions. Microquasar jet termination regions could be detectable at radio wavelengths for current instruments sensitive to ∼arcminute scales. At X-ray energies, the expected luminosities are moderate, although the emitter is more compact than the radio one. The source may be detectable by XMM-Newton or Chandra, with 1-10 arcsec of angular resolution. The radiation at gamma-ray energies may be within the detection limits of the next generation of satellite and ground-based instruments.

Large-scale flow dynamics and radiation in pulsarγ-ray binaries

“…Velázquez & Raga 2000;Heinz 2002;Heinz & Sunyaev 2002;Bosch-Ramon et al 2005;Zavala et al 2008;Bordas et al 2009;Bosch-Ramon et al 2011). On the other hand, PSR B1259−63 is a system formed by an O9.5 V star and a nonaccreting millisecond pulsar (Johnston et al 1992;Negueruela et al 2011).…”

Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations

“…The VHE gamma-ray emission from the SS 433/W50 interaction regions was first considered by Aharonian & Atoyan (1998), who estimated gamma-ray fluxes at a level of ∼ 10 −12 ph cm −2 s −1 for the eastern e3 region produced by electrons scattering off CMB photons. Bordas et al (2009) also considered the non-thermal emission produced in microquasar jets/ISM interaction regions, providing gamma-ray flux estimates as a function of the kinetic power of the jets, age of the system, and particle density of the environment. The application of this model to SS 433/W50 yielded fluxes at the level of ∼10 −13 erg cm −2 s −1 for E > 250 GeV for an assumed distance to the system of 5.5 kpc (Bordas et al 2010), which are roughly at the level of the upper limits reported here.…”

“…The interaction regions between the SS 433 jets and the surrounding W50 nebula could also produce VHE gamma-ray emission, for example through IC scattering of cosmic microwave background (CMB) photons by electrons accelerated at the eastern (e1, e2, e3) and western (w1, w2) termination regions (Safi-Harb & Ögelman 1997;Aharonian & Atoyan 1998;Bordas et al 2009), or through pp interactions if protons are efficiently accelerated at the interaction shocks (Heinz & Sunyaev 2002;Bosch-Ramon et al 2005). Non-thermal emission from these regions has indeed been observed from radio to Xray energies (Brinkmann et al 1996, Dubner et al 1998Safi-Harb & Ögelman 1997;Safi-Harb & Petre 1999;Fuchs 2002;Brinkmann et al 2007.…”

Radio continuum and near-infrared study of the MGRO J2019+37 region

“…It was either completely resolved or is a variable radio source, since no radio emission is expected in the high/soft state of microquasars. In any case, these three sources could be hadronic microquasars whose jets would interact with the ISM accelerating protons (e.g., Heinz & Sunyaev 2002;Bordas et al 2009). The accelerated protons may escape from the accelerating region colliding with the surrounding regions of the ISM, rendering very high-energy emission (e.g., Bosch-Ramon et al 2005).…”

“…To explain steady VHE γ-ray emission, hadronic models have been developed by several authors (e.g., Aharonian & Atoyan 1996;Butt et al 2003;Torres et al 2004;Bordas et al 2009). The electromagnetic radiation produced by both hadronic jets from microquasars and Galactic cosmic rays, and their interaction with the ISM were explored by Bosch-Ramon et al (2005).…”