The importance of radiation pressure in the launching of jets

TL;DR

This paper suggests that high radiation pressure from neutron stars in Z-track sources disrupts the inner accretion disk, diverts accretion flow vertically, and is essential for jet launching, supported by observational and theoretical analysis.

Contribution

It introduces a model linking radiation pressure to jet launching in Z-track sources, supported by extended ADC emission analysis and theoretical burning stability.

Findings

Radiation pressure exceeds Eddington limit on the Horizontal Branch.

Jet presence correlates with high radiation pressure regions.

Flaring results from unstable nuclear burning at critical accretion rates.

Abstract

Based on the results of applying the extended ADC emission model to three Z-track sources: GX340+0, GX5-1 and CygX-2, we propose an explanation of the Z-track sources in which the Normal and Horizontal Branches are dominated by the increasing radiation pressure of the neutron star. The emitted flux becomes several times super-Eddington at the Hard Apex and Horizontal Branch and we suggest that the inner accretion disk is disrupted by this and that part of the accretion flow is diverted vertically. This position on the Z-track is exactly the position where radio emission is detected showing the presence of jets. We thus propose that high radiation pressure is a necessary condition for the launching of jets. We also show that flaring must consist of unstable nuclear burning and that the mass accretion rate per unit emitting area of the neutron star mdot at the onset of flaring agrees well with the critical theoretical value at which burning becomes unstable.