Rapid compact jet quenching in the Galactic black hole candidate X-ray binary MAXI J1535-571

TL;DR

This study observes rapid changes in the jet structure of the black hole binary MAXI J1535-571, revealing that the jet quenching occurs as the acceleration region moves away from the black hole, not due to local particle cooling.

Contribution

The paper provides the first detailed multi-wavelength observation of rapid jet spectral break evolution and links jet quenching to the movement of the acceleration region in a black hole binary.

Findings

Jet spectral break shifts from IR to radio in less than a day.

Jet quenching is caused by the acceleration region moving away from the black hole.

X-ray spectral softening precedes and follows jet changes.

Abstract

We present results from six epochs of quasi-simultaneous radio, (sub-)millimetre, infrared, optical, and X-ray observations of the black hole X-ray binary MAXI~J1535$-$571. These observations show that as the source transitioned through the hard-intermediate X-ray state towards the soft intermediate X-ray state, the jet underwent dramatic and rapid changes. We observed the frequency of the jet spectral break, which corresponds to the most compact region in the jet where particle acceleration begins (higher frequencies indicate closer to the black hole), evolve from the IR band into the radio band (decreasing by $\approx$3 orders of magnitude) in less than a day. During one observational epoch, we found evidence of the jet spectral break evolving in frequency through the radio band. Estimating the magnetic field and size of the particle acceleration region shows that the rapid fading of the high-energy jet emission was not consistent with radiative cooling; instead the particle acceleration region seems to be moving away from the black hole on approximately dynamical timescales. This result suggests that the compact jet quenching is not caused by local changes to the particle acceleration, rather we are observing the acceleration region of the jet travelling away from the black hole with the jet flow. Spectral analysis of the X-ray emission show a gradual softening in the few days before the dramatic jet changes, followed by a more rapid softening $\sim$1--2\,days after the onset of the jet quenching.