Clues to unveil the emitter in LS 5039: powerful jets vs colliding winds

TL;DR

This paper investigates whether LS 5039's TeV gamma-ray emission is better explained by powerful jets or pulsar winds, analyzing observational data and theoretical models to identify the most plausible scenario.

Contribution

The study critically evaluates the pulsar wind and jet scenarios for LS 5039, providing new insights that favor the jet hypothesis based on gamma-ray opacity considerations.

Findings

Pulsar wind scenario is unlikely due to high gamma-ray opacities.

Jet scenario better explains TeV emission with lower photon-photon absorption.

Electromagnetic cascades are inefficient in the star's magnetic environment.

Abstract

LS 5039 is among the most interesting VHE sources in the Galaxy. Two scenarios have been put forward to explain the observed TeV radiation: jets vs pulsar winds. The source has been detected during the superior conjunction of the compact object, when very large gamma-ray opacities are expected. In addition, electromagnetic cascades, which may make the system more transparent to gamma-rays, are hardly efficient for realistic magnetic fields in massive star surroundings. All this makes unlikely the standard pulsar scenario for LS 5039, in which the emitter is the region located between the star and the compact object, where the opacities are the largest. Otherwise, a jet-like flow can transport energy to regions where the photon-photon absorption is much lower and the TeV radiation is not so severely absorbed.