Modeling interaction of relativistic and nonrelativistic winds in binary system PSR 1259-63/SS2883. I.Hydrodynamical limit

TL;DR

This study uses hydrodynamical simulations to explore how relativistic pulsar winds interact with nonrelativistic stellar winds in a binary system, revealing shock formation and high-speed flows without magnetic fields, explaining observed variability.

Contribution

First hydrodynamical simulation of ultrarelativistic pulsar wind interacting with nonrelativistic stellar wind in a binary system, showing shock formation and flow acceleration without magnetic fields.

Findings

Formation of an unclosed pulsar wind termination shock.

High Lorentz factor flow ($b3a0100$) due to hydrodynamical effects.

No magnetic field needed for ultrarelativistic outflow.

Abstract

In this paper, we present a detailed hydrodynamical study of the properties of the flow produced by the collision of a pulsar wind with the surrounding in a binary system. This work is the first attempt to simulate interaction of the ultrarelativistic flow (pulsar wind) with the nonrelativistic stellar wind. Obtained results show that the wind collision could result in the formation of an "unclosed" (at spatial scales comparable to the binary system size) pulsar wind termination shock even when the stellar wind ram pressure exceeds significantly the pulsar wind kinetical pressure. Moreover, the post-shock flow propagates in a rather narrow region, with very high bulk Lorentz factor ($\gamma\sim100$). This flow acceleration is related to adiabatical losses, which are purely hydrodynamical effects. Interestingly, in this particular case, no magnetic field is required for formation of the ultrarelativistic bulk outflow. The obtained results provide a new interpretation for the orbital variability of radio, X-ray and gamma-ray signals detected from binary pulsar system PSR 1259-63/SS2883.