Quasiperiodic oscillations and Tomimatsu-Sato {\delta} = 2 space-time

TL;DR

This paper models low-mass X-ray binary spacetimes using the Tomimatsu-Sato {}=2 metric, analyzing orbital frequencies, and finds that their properties are similar to Kerr black holes, with implications for stellar black hole estimates.

Contribution

It introduces the use of the Tomimatsu-Sato {}=2 metric for modeling X-ray binary spacetimes and compares its oscillation frequencies to Kerr black holes, applying the nonlinear resonance model.

Findings

Characteristic frequencies are similar to Kerr black holes.

The nonlinear resonance model predictions agree with observed black hole estimates.

Estimates for black hole angular momenta are consistent with literature.

Abstract

We model the spacetime of low-mass X-ray binaries with the Tomimatsu-Sato {\delta} = 2 (TS2) metric and study the properties of the orbital and the epicyclic frequencies. The numerical analysis shows that the properties of the characteristic frequencies of oscillation do not differ qualitatively from those of the Kerr black hole. Estimates for the angular momenta of the three stellar mass black hole candidates GRO 1655-40, XTE 1550-564 and GRS 1915+105 are made with the application of the nonlinear resonance model. We find agreement between the predictions based on the 3 : 2 nonlinear resonance model for a TS2 background and the current estimates found in the literature.