Links Between Z Sources and Atoll Sources

TL;DR

This paper proposes that Z and atoll sources are different evolutionary phases of neutron stars in low mass X-ray binaries, rather than distinct source types, based on their differing Q-$ u$ relations of lower kHz QPOs.

Contribution

It introduces a new evolutionary framework linking Z and atoll sources as phases in neutron star development within LMXBs.

Findings

Z and atoll sources share a common evolutionary track.

Differences in Q-$ u$ relations reflect different phases.

Supports the phase-based model over the distinct-source classification.

Abstract

It is known that the Z and atoll sources are two typical types of neutron-star sources in low mass X-ray binaries (LMXBs), which present very different Q-$\nu$ relations of lower kHz QPOs. We propose that the Z and atoll sources are two different phases in the evolutionary track of neutron star in LMXBs, instead of two types of distinct sources.