Hydrodynamics of interaction of pulsar and stellar winds and its impact on the high energy radiation of binary pulsar systems

TL;DR

This paper models the hydrodynamic interaction between pulsar and stellar winds in binary systems, revealing how relativistic effects influence high-energy radiation variability, especially gamma-ray emissions, due to anisotropic inverse Compton scattering and Doppler boosting.

Contribution

It provides a self-consistent hydrodynamic model of pulsar-stellar wind interactions that explains observed gamma-ray variability and the dominance of adiabatic losses in such systems.

Findings

Relativistic pulsar wind flow reaches Lorentz factors up to 4.

Anisotropic inverse Compton radiation causes variable gamma-ray signals.

Adiabatic losses dominate over radiative losses in the system.

Abstract

The hydrodynamics of the interaction of pulsar and stellar winds in binary systems harboring a pulsar and its impact on the nonthermal radiation of the binary pulsar PSR B1259-63/SS2883 is discussed. The collision of an ultrarelativistic pulsar wind with a nonrelativistic stellar outflow results in significant bulk acceleration of the shocked material from the pulsar wind. Already at distances comparable to the size of the binary system, the Lorentz factor of the shocked flow can be as large as $\gamma$~4. This results in significant anisotropy of the inverse Compton radiation of accelerated electrons. Because of the Doppler boosting of the produced radiation, one should expect a variable gamma-ray signal from the system. In particular, this effect may naturally explain the reported tendency of a decrease of TeV gamma-ray flux close to the periastron. The modeling of the interaction of pulsar and stellar winds allows self-consistent calculations of adiabatic losses. Our results show that adiabatic losses dominate over the radiative losses. These results have direct impact on the orbital variability of radio, X-ray and gamma-ray signals detected from the binary pulsar PSR 1259-63/SS2883.