Influence of mass of black holes on radio/X-ray correlation diagram

TL;DR

This study examines how black hole mass affects the radio/X-ray correlation in black hole X-ray binaries, exploring whether mass influences the observed dual-track behavior in the correlation diagram.

Contribution

It investigates the impact of black hole mass on the radio/X-ray correlation, considering uncertainties in mass estimates and luminosity measurements, to explain the dual-track phenomenon.

Findings

Black hole mass may significantly influence the correlation track.

Current mass estimates and luminosity data have large uncertainties.

Sources may transition between correlation tracks over time.

Abstract

The radio/X-ray correlation diagram, for Black Hole X-ray Binaries (BHXBs) in the hard state, depicts the connection that might exists between the radio jets and X-ray emitting accretion discs. The current version of the radio/X-ray correlation diagram shows two populations of BHXBs. These two populations evolve along two different correlation tracks ($F_{rad}= \kappa F_{x}^{b}$), namely the standard track and the outliers. Over the past years, the key question has been to explain the existence of these two tracks. In this paper, we investigate the impact of the black hole mass on the radio/X-ray correlation for a sample of 17 BHXBs. We are led to conclude at least one of the following with full consideration of large uncertainties in mass estimates:(i) Most of the reported mass estimates of black holes are incorrect or insufficiently accurate to infer their impact on radio/X-ray correlation diagram. (ii) The estimated radio luminosities and X-ray luminosites are still not reliable enough for two reasons. One reason is due to the lack of associated errors in observational data. Another is that some sources might still transit from one track to the other. (iii) The mass of BH has a significant influence on which track, the source belongs to, on a radio/X-ray correlation diagram.