Numerical analysis of quasiperiodic oscillations in the Hartle-Thorne spacetime

Abstract Within the framework of general relativity, we numerically analyse quasiperiodic oscillations (QPOs) observed in low-mass X-ray binary systems containing neutron stars (NSs). Using the Relativistic Precession Model (RPM), formulated by Stella and Morsink, we examine QPO data from eight NSs. We apply expressions for the fundamental frequencies of test particles in the gravitational field of a slowly rotating, slightly deformed compact object described by a Hartle–Thorne (HT) metric, which closely represents a rotating NS. Employing Markov-Chain-Monte-Carlo (MCMC) analyses with the Metropolis–Hastings algorithm, we estimate the parameters of compact objects, including their 1–σ error bar. Finally, we compare our results with predictions based on consideration of the Schwarzschild metric, which has just one free parameter. Despite the two additional free spacetime parameters, we show that only one of the eight sources can be satisfactorily explained within the RPM when the HT metric is considered. This conclusion holds under the a priori limit on NS angular momentum adopted in our analysis, namely j < 0.7.