The kHz QPOs of Neutron Stars and Millisecond Pulsars and Implications

TL;DR

This paper reviews the properties, correlations, and implications of kilohertz QPOs in neutron star low mass X-ray binaries, discussing their mechanisms and what they reveal about neutron star characteristics.

Contribution

It provides a comprehensive summary of kHz QPO observations, correlations, and their implications for neutron star properties, highlighting recent insights and unresolved questions.

Findings

Twin kHz QPOs show specific correlation patterns.

No clear link between NS spin and QPOs.

Implications for NS mass, radius, and magnetic field.

Abstract

The kilohertz quasi-periodic oscillations (kHz QPOs) have been found in neutron star low mass X-ray binaries (NS-LMXBs), which present the millisecond timing phenomena close to the surface of the compact objects. We briefly summarize the following contents: (1). The correlations and distributions of twin kHz QPOs; (2). The relations of high-low frequency QPOs; (3). The QPO properties of NS Atoll and Z sources; (4). No clear direct correlations between NS spins and QPOs; (5). The mechanisms of kHz QPOs; (6). The implications of kHZ QPOs, e.g., NS mass and radius, disk thickness and magnetic field of Atoll and Z source.