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 the TeV X-ray binary LS 5039, providing evidence favoring a non-accreting pulsar scenario over a microquasar model.

Contribution

The paper presents high-resolution VLBA observations that reveal morphological changes consistent with a pulsar wind interaction rather than accretion-driven jets.

Findings

Morphological changes align with pulsar wind models

Core flux density remains stable over observations

Results challenge the microquasar 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.