Radio-X-ray Time Lags in GX 339-4: Probing Magnetic Field Transport in Black Hole Accretion

TL;DR

This study analyzes radio and X-ray time delays in GX 339-4 to understand magnetic field transport and jet-accretion coupling during outbursts.

Contribution

It introduces a method to measure and interpret radio-X-ray time lags, linking them to magnetic field dynamics in black hole accretion systems.

Findings

Radio emission precedes X-ray in rising hard state by ~3 days.

Radio emission lags X-ray in decaying hard state by ~8 days.

Magnetic field estimates explain observed time delay patterns.

Abstract

We present an analysis of the time delay between the radio emission and the X-ray Compton luminosity during the 2010-2011 outburst of GX 339-4. Using the interpolated cross-correlation function (ICCF), we measure the time delay between the Compton luminosity and the radio luminosity, and find that during the rising hard state, the radio emission precedes the Compton luminosity by approximately 3 days. In contrast, in the decaying hard state, the radio emission lags behind the Compton luminosity by about 8 days. By estimating the mass accretion rate and the disk truncation radius, the calculated inner magnetic field can account for both the radio delay in the decaying hard state and the radio precedence in the rising hard state. The time delays observed in different outbursts across multiple sources are compared further, and the underlying physical mechanisms account for this difference are discussed. These results provide insights into the evolving coupling between the inner accretion flow and the jet in black hole X-ray binaries.