Exploring the powering source of the TeV X-ray binary LS 5039

TL;DR

This study uses VLBA observations to investigate the powering source of LS 5039, finding evidence more consistent with a non-accreting pulsar than a microquasar scenario.

Contribution

The paper provides high-resolution VLBA data that help distinguish between pulsar wind interaction and microquasar models for LS 5039.

Findings

Extended emission morphology varies rapidly, inconsistent with microquasar predictions.

Core flux density remains stable over observations.

Results support the non-accreting pulsar scenario.

Abstract

LS 5039 is one of the four TeV emitting X-ray binaries detected up to now. The powering source of its multi-wavelength emission can be accretion in a microquasar scenario or wind interaction in a young non-accreting pulsar scenario. These two scenarios predict different morphologic and peak position changes along the orbital cycle of 3.9 days, which can be tested at milliarcsecond scales using VLBI techniques. Here we present a campaign of 5 GHz VLBA observations conducted in June 2000 (2 runs five days apart). The results show a core component with a constant flux density, and a fast change in the morphology and the position angle of the elongated extended emission, but maintaining a stable flux density. These results are difficult to fit comfortably within a microquasar scenario, whereas they appear to be compatible with the predicted behavior for a non-accreting pulsar.