The effects of the stellar wind and orbital motion on the jets of high-mass microquasars

Abstract

High-mass microquasar jets propagate under the effect of the wind from the companion star, and the orbital motion of the binary system. The stellar wind and the orbit may be dominant factors determining the jet properties beyond the binary scales.} An analytical study is performed to characterize the effects of the stellar wind and the orbital motion on the jet properties. Accounting for the wind thrust transferred to the jet, we derive analytical estimates to characterize the jet evolution under the impact of the stellar wind. We include the Coriolis force effect, induced by orbital motion and enhanced by the wind presence. Large-scale evolution of the jet is sketched accounting for wind-to-jet thrust transfer, total energy conservation, and wind-jet flow mixing. If the angle of the wind-induced jet bending is larger than its half-opening angle, the following is expected: (i) a strong recollimation shock; (ii) bending against orbital motion, caused by Coriolis forces and enhanced by the wind presence; and (iii) non-ballistic helical propagation further away. Even if disrupted, the jet can reaccelerate due to ambient pressure gradients, but wind entrainment can weaken this acceleration. On large scales, the opening angle of the helical structure is determined by the wind-jet thrust relation, and the wind-loaded jet flow can be rather slow. The impact of stellar winds on high-mass microquasar jets can yield non-ballistic helical jet trajectories, jet partial disruption and wind mixing, shocks, and possibly non-thermal emission. Among several observational diagnostics at different bands, the radio morphology on milliarcsecond scales can be particularly insightful regarding the wind-jet interaction.