Observational Signatures of Mass-Loading in Jets Launched by Rotating Black Holes

TL;DR

This paper explores how the presence of plasma in black hole jets affects observable signals, using simulations to differentiate between empty and filled funnels, with implications for interpreting astronomical observations.

Contribution

It provides the first detailed observational signatures of mass-loading in black hole jets through radiative transfer calculations on 3D GRMHD simulations.

Findings

Significant optical and X-ray differences between empty and plasma-filled funnels.

Current Sgr A* data constrains jet filling only for rapidly rotating black holes.

Implications for Event Horizon Telescope observations and X-ray binary states.

Abstract

It is widely believed that relativistic jets in X-ray binaries and active-galactic nuclei are powered by the rotational energy of black holes. This idea is supported by general-relativistic magnetohydrodynamic (GRMHD) simulations of accreting black holes, which demonstrate efficient energy extraction via the Blandford-Znajek mechanism. However, due to uncertainties in the physics of mass-loading, and the failure of GRMHD numerical schemes in the highly-magnetized funnel region, the matter content of the jet remains poorly constrained. We investigate the observational signatures of mass-loading in the funnel by performing general-relativistic radiative transfer calculations on a range of 3D GRMHD simulations of accreting black holes. We find significant observational differences between cases in which the funnel is empty and cases where the funnel is filled with plasma, particularly in the optical and X-ray bands. In the context of Sgr A*, current spectral data constrains the jet filling only if the black hole is rapidly rotating with $a\gtrsim0.9$. In this case, the limits on the infrared flux disfavour a strong contribution from material in the funnel. We comment on the implications of our models for interpreting future Event Horizon Telescope observations. We also scale our models to stellar-mass black holes, and discuss their applicability to the low-luminosity state in X-ray binaries.