Dynamical Effects of Colliding Outflows in Binary Systems

The outflow of an object traveling in a fluid can shape the fluid morphology by forming a forward bow shock that accelerates the object via gravitational feedback. This dynamical effect, namely, dynamical antifriction, has been studied in idealized infinite uniform media, which suffers from the convergence problem due to the long-range nature of gravitation. In this work, we conduct global 3D hydrodynamic simulations to study this effect in the scenario of a binary system, where the collision of outflows from both stars creates a suitable configuration. We demonstrate with simulations that a dense and slow outflow can give rise to a positive torque on the binary and lead to the expansion of the orbit. As an application, we show that binaries consisting of an AGB star and an outflowing pulsar can experience similar to 10% orbital expansion during the AGB stage, in addition to the contribution from mass loss. We also prove that the gravitational force drops as O(r (-3)) from the center of mass in the binary scenarios, which guarantees a quick converge of the overall effect.

Automated summary

In this study, the dynamical antifriction effect in a binary system was investigated using global 3D hydrodynamic simulations. The simulations showed that a dense and slow outflow can lead to orbital expansion, and it was proved that the gravitational force converges quickly in binary scenarios.