QPOs in compact sources as a non-linear hydrodynamical resonance: Determining spin of compact objects

TL;DR

This paper presents a unified non-linear hydrodynamical resonance model explaining the origin of QPOs in compact objects, linking their frequencies to accretion disk modes and the spin of the objects, and deriving astrophysical parameters.

Contribution

It introduces a novel unified model attributing QPOs to nonlinear resonance of accretion disk modes influenced by the compact object's spin, explaining a wide frequency range.

Findings

Higher frequency QPOs explained by the model for black holes and neutron stars.

Model predicts black hole spins and constrains neutron star radii and masses.

Resonance conditions depend on accretion flow properties.

Abstract

Origin of wide varieties of quasi-periodic oscillation (QPO) observed in compact sources is still not well established. Its frequencies range from mHz to kHz spanning all compact objects. Are different QPOs, with different frequencies, originating from different Physics? We propose that the emergence of QPOs is the result of nonlinear resonance of fundamental modes present in accretion disks forced by external modes including that of the spin of the underlying compact object. Depending on the properties of accreting flow, e.g. its velocity and gradient, resonances, and any mode locking, take place at different frequencies, exhibiting low to high frequency QPOs. We explicitly demonstrate the origin of higher frequency QPOs for black holes and neutron stars by a unified model and outline how the same physics could be responsible to produce lower frequency QPOs. The model also predicts the spin of black holes, and constrains the radius of neutron stars and the mass of both.