We present Neutron Star Interior Composition Explorer X-ray and Arcminute Microkelvin Imager Large Array radio observations of a rapid hard-to-soft state transition in the black hole X-ray transient MAXI J1820+070. During the transition from the hard state to the soft state a switch between two particular types of quasiperiodic oscillations (QPOs) was seen in the X-ray power density spectra, from type-C to type-B, along with a drop in the strength of the broadband X-ray variability and a brief flare in the 7-12 keV band. Soon after this switch (~1.5-2.5 hr) a strong radio flare was observed that corresponded to the launch of superluminal ejecta. Although hints of a connection between QPO transitions and radio flares have been seen in other black hole X-ray transients, our observations constitute the strongest observational evidence to date for a link between the appearance of type-B QPOs and the launch of discrete jet ejections.
@article{arxiv.2003.01012,
title = {A rapid change in X-ray variability and a jet ejection in the black hole transient MAXI J1820+070},
author = {Jeroen Homan and Joe Bright and Sara E. Motta and Diego Altamirano and Zaven Arzoumanian and Arkadip Basak and Tomaso M. Belloni and Edward M. Cackett and Rob Fender and Keith C. Gendreau and Erin Kara and Dheeraj R. Pasham and Ronald A. Remillard and James F. Steiner and Abigail L. Stevens and Phil Uttley},
journal= {arXiv preprint arXiv:2003.01012},
year = {2020}
}