No evidence for black hole spin powering of jets in X-ray binaries

TL;DR

This study investigates the relationship between black hole spin and jet properties in X-ray binaries, finding no evidence of correlation and suggesting alternative explanations for jet variability.

Contribution

It provides the first comprehensive comparison of black hole spin measurements with jet power and speed across all accretion states, challenging the spin-jet connection hypothesis.

Findings

No correlation between jet properties and black hole spin.

Jet power and radiative efficiency vary independently of spin.

Multiple mechanisms influence jet variability beyond spin effects.

Abstract

In this paper we take the reported measurements of black hole spin for black hole X-ray binaries, and compare them against measurements of jet power and speed across all accretion states in these systems. We find no evidence for any correlation between the properties of the jets and the reported spin measurements. These constraints are strongest in the hard X-ray state, which is associated with a continuous powerful jet. We are led to conclude that one or more of the following is correct: (i) the calculated jet power and speed measurements are wrong, (ii) the reported spin measurements are wrong, (iii) there is no strong dependence of the jet properties on black hole spin. In addition to this lack of observational evidence for a relation between black hole spin and jet properties in stellar mass black holes, we highlight the fact that there appear to be at least three different ways in which the jet power and/or radiative efficiency from a black hole X-ray binary may vary, two of which are certainly independent of spin because they occur in the same source on relatively short timescales, and the third which does not correlate with any reported measurements of black hole spin. We briefly discuss how these findings may impact upon interpretations of populations of active galactic nuclei in the context of black hole spin and merger history.