Radio flaring and dual radio loud/quiet behaviour in the new candidate black hole X-ray binary MAXI J1631-472

TL;DR

This study monitors the black hole candidate MAXI J1631-472 during its 2018-2019 outburst, revealing radio flares, dual radio loud/quiet behavior, and state-dependent jet activity, contributing to understanding black hole accretion and jet physics.

Contribution

It provides detailed multi-wavelength observations of MAXI J1631-472, highlighting its complex radio and X-ray state transitions and jet behavior, especially the radio quietness at high luminosities.

Findings

Radio flares occur after state transitions.

The source is radio quiet at high luminosities.

Rejoins the standard radio:X-ray correlation at lower luminosities.

Abstract

We present the results of a weekly monitoring of the new black hole candidate X-ray binary MAXI J1631-472 carried out with the MeerKAT radio interferometer, the Neil Gehrels Swift Observatory, and the Monitor of All-sky X-ray Image (MAXI) instrument, during its 2018-2019 outburst. The source exhibits a number of X-ray states, in particular both high- and low-luminosity hard states bracketed by extended soft states. Radio flaring is observed shortly after a transition from hard/intermediate states to the soft state. This is broadly in agreement with existing empirical models, but its extended duration hints at multiple unresolved flares and/or jet-ISM interactions. In the hard state radio:X-ray plane, the source is revealed to be 'radio quiet' at high luminosities, but to rejoin the `standard' track at lower luminosities, an increasingly commonly-observed pattern of behaviour.