Global simulations of the interaction of microquasar jets with a stellar wind in high-mass X-ray binaries

Jets powered by high-mass X-ray binaries must traverse the powerful wind of the companion star. We present the first global three-dimensional simulations of jet–wind interaction in high-mass X-ray binaries. We show that the wind momentum flux intercepted by the jet can lead to significant bending of the jet and that jets propagating through a spherical wind will be bent to an asymptotic angle ${\psi }_{\infty }$. We derive simple expressions for ${\psi }_{\infty }$ as a function of jet power and wind thrust. For known wind parameters, measurements of ${\psi }_{\infty }$ can be used to constrain the jet power. In the case of Cygnus X-1, the lack of jet precession as a function of orbital phase observed by the Very Long Baseline Array can be used to put a lower limit on the jet power of $L_{jet}\gtrsim {10}^{36}ergs{s}^{-1}$. We further discuss the case where the initial jet is inclined relative to the binary orbital axis. We also analyze the case of Cygnus X-3 and show that jet bending is likely negligible unless the jet is significantly less powerful or much wider than currently thought. Our numerical investigation is limited to isotropic stellar winds. We discuss the possible effects of wind clumping on jet–wind interaction, which are likely significant, but argue that our limits on jet power for Cygnus X-1 are likely unaffected by clumping unless the global wind mass-loss rate is orders of magnitude below the commonly assumed range for Cyg X-1.