The physics of kHz QPOs---strong gravity's coupled anharmonic oscillators

TL;DR

This paper proposes that high-frequency QPOs in neutron stars and black holes originate from non-linear resonances caused by strong gravity, explaining observed frequencies through coupled anharmonic oscillators.

Contribution

It introduces a novel non-linear resonance model linking QPOs to strong gravity effects, explaining observed frequency ratios in accreting compact objects.

Findings

Resonance model matches observed 300 Hz and 450 Hz QPOs in GRO J1655-40.

Strong gravity causes deviations from Newtonian potential, enabling resonances.

The theory provides a unified explanation for QPOs in neutron stars and black holes.

Abstract

We explain the origin of the puzzling high frequency peaks (QPOs) in the variability power spectra of accreting neutron stars and black holes as a non-linear 1:2 or 1:3 resonance between orbital and radial epicyclic motion. These resonances are present because the gravitational field deviates strongly from a Newtonian 1/r potential. Our theory agrees with the recently reported observations of two QPOs, at 300 Hz and 450 Hz, in the black hole candidate GRO J1655-40.