Radio emission from high-mass binaries with non-accreting pulsars

TL;DR

This paper models radio emission from high-mass binaries with non-accreting pulsars, revealing insights into the flow dynamics and magnetic properties of the shocked wind regions through synthetic emission maps.

Contribution

It introduces a numerical framework for simulating radio emission in such binaries, linking shock flow properties to observable radio features.

Findings

The emitting flow is likely slow-moving.

Pulsar wind magnetization at the shock is higher than in isolated pulsars.

Synthetic maps can be compared with observations to infer flow characteristics.

Abstract

Binary systems that harbor a non-accreting pulsar are efficient non-thermal emitters, from radio to gamma rays. This broadband emission is thought to come from the region where the companion star and pulsar winds collide. A paradigmatic example of this source type is PSR B1259$-$63. Whereas the high-energy radiation probes the shock structure at the binary scale, the radio emission is produced well outside the system, in regions where the shocked stellar and pulsar winds are likely mixing due to hydrodynamical instabilities. Understanding the evolution of the shocked flow depends strongly on a proper characterization of the low-energy radiation. We have performed numerical calculations of the radio emission produced in a high-mass binary hosting a young pulsar. Adopting a prescription for the shocked flow in the system and the non-thermal particle injection, we have generated synthetic radio emission maps that can be compared with observations. Preliminary results suggest that the emitting bulk flow should be rather slow, with a pulsar wind magnetization at the shock higher than in isolated pulsars.