MeerKAT radio detection of the Galactic black hole candidate Swift J1842.5-1124 during its 2020 outburst

TL;DR

This study reports the first radio detection of the Galactic black hole candidate Swift J1842.5-1124 during its 2020 outburst, demonstrating its radio/X-ray behavior aligns with established black hole accretion models.

Contribution

It provides the first radio detection of Swift J1842.5-1124 during an outburst and analyzes its radio/X-ray correlation, supporting the disk-jet coupling model in black hole binaries.

Findings

First radio detection of Swift J1842.5-1124 during outburst

Radio and X-ray properties consistent with disk-jet coupling

Source likely located beyond 5 kpc if following black hole correlation

Abstract

Swift J1842.5$-$1124 is a transient Galactic black hole X-ray binary candidate, which underwent a new outburst in May 2020. We performed multi-epoch MeerKAT radio observations under the ThunderKAT Large Survey Programme, coordinated with quasi-simultaneous Swift/XRT X-ray observations during the outburst, which lasted nearly a month. We were able to make the first-ever radio detection of this black hole binary with the highest flux density of 229$\pm$31 $\mu$Jy when the source was in the hard state, after non-detection in the radio band in the soft state which occurred immediately after its emergence during the new X-ray outburst. Therefore, its radio and X-ray properties are consistent with the disk-jet coupling picture established in other black hole X-ray binaries. We place the source's quasi-simultaneous X-ray and radio measurements on the radio/X-ray luminosity correlation plane; two quasi-simultaneous radio/X-ray measurements separated by 11 days were obtained, which span $\sim$ 2 dex in the X-ray luminosity. If the source follows the black hole track in the radio/X-ray correlation plane during the outburst, it would lie at a distance beyond $\sim$ 5 kpc.