Resonant switch model of twin peak HF QPOs applied to the atoll source 4U 1636-53

TL;DR

This paper introduces a Resonant Switch model for twin peak HF QPOs in neutron stars, explaining frequency shifts at resonant points and constraining the star's mass and spin.

Contribution

It proposes a novel Resonant Switch model that accounts for mode transitions at resonant points, providing new insights into HF QPOs in neutron stars.

Findings

Identifies two resonant points at frequency ratios 3:2 and 5:4.

Constrains neutron star mass and spin parameters.

Explains mode switching due to non-linear resonance phenomena.

Abstract

We present a Resonant Switch (RS) model of twin peak high-frequency quasi-periodic oscillations (HF QPOs), assuming switch of twin oscillations at a resonant point, where frequencies of the upper and lower oscillations $\nu_U$ and $\nu_L$ become to be commensurable and the twin oscillations change from one pair of the oscillating modes (corresponding to a specific model of HF QPOs) to some other pair due to non-linear resonant phenomena. The RS model enables to determine range of allowed values of spin $a$ and mass $M$ of the neutron star located at the atoll source 4U 1636-53 where two resonant points are observed at frequency ratios $\nu_U:\nu_L$ = 3:2, 5:4.