# Sub-second variability in black-hole X-ray binary jets

## TL;DR

This paper reviews recent advances in studying black-hole X-ray binary jets through sub-second multi-wavelength variability, revealing how inflow fluctuations influence jet behavior using cross-spectral analysis.

## Contribution

It introduces a new approach to analyze jet physics via rapid variability studies and summarizes recent findings from cross-spectral analysis techniques.

## Key findings

- Detection of sub-second IR fluctuations lagging X-rays by ~0.1 s
- Evidence of inflow-to-jet fluctuation transfer
- Enhanced understanding of jet base physical processes

## Abstract

In the last 10 years multi-wavelength fast variability studies of low mass X-ray binaries have shown a dramatic development. A key discovery was the detection of O-IR sub-second fluctuations in two black-hole transients, lagging the X-rays by $\approx$0.1 s. This demonstrated how the fluctuations observed in the inflow could be transferred to the jet, allowing therefore also to study in a completely new way the physical processes which take place at the base of the jet. In this paper we review the latest developments of the study of jets with this new approach, focusing on the results obtained with cross-spectral analysis techniques.