A model for upper kHz QPO coherence of accreting neutron star

TL;DR

This paper presents a theoretical model explaining the coherence of upper kHz QPOs in accreting neutron stars by linking it to the radial extent of the emission region at the magnetosphere-disk boundary, and validates it with observational data.

Contribution

It introduces a new theoretical model connecting QPO coherence to the emission region size and applies it successfully to observational data from multiple sources.

Findings

Model explains the Q-factor of upper kHz QPOs.

Consistent with observational data from Atoll and Z sources.

Provides insights into the emission region at the magnetosphere-disk boundary.

Abstract

{We investigate the coherence of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in the low-mass X-ray binary (LMXB) theoretically. The profile of upper kHz QPO, interpreted as Keplerian frequency, is ascribed to the radial extent of the kHz QPO emission region, associated with the transitional layer at the magnetosphere-disk boundary, which corresponds to the coherence of upper kHz QPO. The theoretical model for Q-factor of upper kHz QPO is applied to the observational data of five Atoll and five Z sources, and the consistence is implied.