3D RMHD simulations of jet-wind interactions in high-mass X-ray binaries

Abstract

Context. Relativistic jets are ubiquitous in the Universe. In microquasars, especially in high-mass X-ray binaries, the interaction of jets with the strong winds driven by the massive and hot companion star in the vicinity of the compact object is fundamental for understanding the jet dynamics, nonthermal emission, and long-term stability. However, the role of the jet magnetic field in this process is unclear. In particular, it is still debated whether the magnetic field favors jet collimation or triggers more instabilities that can jeopardize the jet evolution outside the binary. Aims. We study the dynamical role of weak and moderate to strong toroidal magnetic fields during the first several hundred seconds of jet propagation through the stellar wind, focusing on the magnetized flow dynamics and the mechanisms of energy conversion. Methods. We developed the code Lóstrego v1.0, a new 3D relativistic magnetohydrodynamics code to simulate astrophysical plasmas in Cartesian coordinates. Using this tool, we performed the first 3D relativistic magnetohydrodynamics numerical simulations of relativistic magnetized jets propagating through the clumpy stellar wind in a high-mass X-ray binary. To highlight the effect of the magnetic field in the jet dynamics, we compared the results of our analysis with those of previous hydrodynamical simulations. Results. The overall morphology and dynamics of weakly magnetized jet models is similar to previous hydrodynamical simulations, where the jet head generates a strong shock in the ambient medium and the initial overpressure with respect to the stellar wind drives one or more recollimation shocks. On the timescales of our simulations (i.e., t < 200 s), these jets are ballistic and seem to be more stable against internal instabilities than jets with the same power in the absence of fields. However, moderate to strong toroidal magnetic fields favor the development of current-driven instabilities and the disruption of the jet within the binary. A detailed analysis of the energy distribution in the relativistic outflow and the ambient medium reveals that magnetic and internal energies can both contribute to the effective acceleration of the jet. Moreover, we verified that the jet feedback into the ambient medium is highly dependent on the jet energy distribution at injection, where hotter, more diluted and/or more magnetized jets are more efficient. This was anticipated by feedback studies in the case of jets in active galaxies.

Modeling the effects of clumpy winds in the high-energy light curves of γ-ray binaries

“…Indeed, shortterm variability of high-energy emission seems to be a common feature in gamma-ray binaries (e.g., Bosch-Ramon et al 2005;Smith et al 2009;Takahashi et al 2009;Rea & Torres 2011;An et al 2015;Tam et al 2018). Studies of the clumpy-wind presence have also been performed, for instance, in the context of massive-star binaries (Pittard 2007), accreting X-ray sources (e.g., Oskinova et al 2012), and microquasars (e.g., Araudo et al 2009;Owocki et al 2009;López-Miralles et al 2022).…”

Numerical simulations of relativistic jets

“…This plot shows relevant information about the field structure in the jet spine, which was hidden by the mixed plasma in the cocoon in our representation in López-Miralles et al. (2022). Since the magnetic field within the cocoon is low compared with that in the jet, we have applied a linear transparency to the field lines, weighted by the field vector module.…”

“…The RMHD simulations are run with the code lóstrego (López-Miralles et al. 2022), which uses the same basic strategy, although with different schemes: (i) primitive variables are reconstructed using piecewise linear methods: MinMod (Roe 1986), monotonized central (MC) (van Leer 1977) or VanLeer (van Leer 1974), with slope limiters that preserve monotonicity (Suresh & Huynh 1997), (ii) the approximate solvers used to compute the fluxes are Harten-Lax-Van Leer (HLL) (Harten, Lax & van Leer 1983), HLLC (Mignone & Bodo 2006) and HLLD (Mignone, Ugliano & Bodo 2009). In this case, the divergence-free condition of the field is maintained by using the constrained transport technique (Evans & Hawley 1988; Ryu et al.…”

“…2010 a ; Perucho & Bosch-Ramon 2012), we run a set of dedicated three-dimensional numerical simulations using our new code lóstrego , including the dynamical effects of magnetic fields (López-Miralles et al. 2022). The results of these simulations showed that the latter could play a stabilizing role – and thus, to provide extra collimation within the binary scale – in the jet evolution when the flux of magnetic energy is low compared with the flux of kinetic energy, while a non-negligible magnetic energy flux makes the jet prone to the development of current-driven instabilities within the scale of the binary.…”

“…2017; López-Miralles et al. 2022), even far from the sub-milliarscsecond resolution achieved by very large baseline interferometry at cm–mm wavelengths in the radio band. Furthermore, the transition of the jet from these compact regions () to parsec scales () has been barely studied by numerical simulations, and only few works have been devoted to microquasar jet evolution at the largest scales (e.g.…”