A precise determination of angular momentum in the black hole candidate GRO J1655-40

TL;DR

This paper uses observed high-frequency QPOs in GRO J1655-40 to precisely estimate the black hole's angular momentum, assuming a resonance model between orbital and epicyclic motions.

Contribution

It provides a novel method to determine black hole spin by linking QPO frequency ratios to angular momentum estimates.

Findings

Angular momentum range: 0.2 to 0.65 for the black hole.

QPO frequencies in 3:2 ratio support resonance model.

Black hole mass estimated between 5.5 and 7.9 solar masses.

Abstract

We note that the recently discovered 450 Hz frequency in the X-ray flux of the black hole candidate GRO J1655-40 is in a 3:2 ratio to the previously known 300 Hz frequency of quasi-periodic oscillations (QPO) in the same source. If the origin of high frequency QPOs in black hole systems is a resonance between orbital and epicyclic motion of accreting matter, as suggested previously, the angular momentum of the black hole can be accurately determined, given its mass. We find that the dimensionless angular momentum is in the range $0.2<j<0.65$ if the mass is in the (corresponding) range of 5.5 to 7.9 solar masses.