Rapid jet production and suppression during fast state transitions in the black hole X-ray binary MAXI J1348–630

¹ INAF Osservatorio Astronomico di Roma Via Frascati 33 I-00078 Monte Porzio Catone (RM), Italy
² Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences 19B Yuquan Road Beijing 100049, People’s Republic of China
³ School of Physics & Astronomy, University of Southampton SO17 1BJ, UK
⁴ Université Paris Cité and Université Paris Saclay, CEA, CNRS, AIM F-91190 Gif-sur-Yvette, France
⁵ International Centre for Radio Astronomy Research – Curtin University GPO Box U1987 Perth WA 6845, Australia

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 8 September 2025
Accepted: 20 January 2026

Abstract

Black hole X-ray binaries (BH XRBs) launch powerful relativistic jets during bright outburst phases. The properties of these outflows change dramatically between different spectral-accretion states. Compact jets are observed during the hard state and are quenched during the soft state, while discrete ejecta are mainly launched during the hard-to-soft state transition. Currently, we do not understand what triggers the formation and/or destruction of compact jets or the launch of discrete ejecta. In this context, finding a unique link between the jet evolution and the properties of the X-ray emission, such as its fast variability, would imply major progress in our understanding of the fundamental mechanisms that drive relativistic outflows in BH XRBs. Here we show that a brief, strong radio re-brightening during a predominantly soft state of the BH XRB MAXI J1348–630 was contemporaneous with a significant increase in the X-ray root-mean-square (rms) variability observed with the Neutron Star Interior Composition Explorer (NICER) in 2019. During this phase, the variability displayed significant changes and, at the same time, MAXI J1348–630 launched two relativistic discrete ejecta that we detected with the MeerKAT and ATCA radio-interferometers. We propose that short-lived compact jets were reactivated during this excursion to the hard-intermediate state and were switched off before the ejecta launch, a behavior that has been very rarely observed in these systems. Interestingly, with the caveat of gaps in our radio and X-ray coverage, we suggest a tentative correspondence between the launch of ejecta and the drop in X-ray rms variability in this source, while other typical X-ray signatures associated with discrete ejections are not detected. We discuss how these results provide us with insights into the complex dynamic coupling between the jets and hot corona in BH XRBs.