A Decade of Black-Hole X-ray Binary Transients

TL;DR

Over the past decade, enhanced multi-wavelength observations of black-hole X-ray binary transients have revealed detailed outburst behaviors, outflows, and accretion disc evolution, highlighting the importance of comprehensive monitoring.

Contribution

This review synthesizes a decade of observational data, emphasizing the advances in monitoring capabilities and their impact on understanding black-hole X-ray binary transients.

Findings

Detection of two of the brightest X-ray outbursts ever observed.

Observation of variable period optical dipping in Swift J1357.2-0933.

Discovery of irradiation-driven disc warp during outburst transition.

Abstract

The last decade has seen a significant gain in both space and ground-based monitoring capabilities, producing vastly better coverage of BH X-ray binaries during their (rare) transient events. This interval included two of the three brightest X-ray outbursts ever observed, namely V404 Cyg in 2015, and MAXI J1820+070 in 2018, as well as the outburst of Swift J1357.2-0933, the first such system to show variable period optical dipping. There are now superb multi-wavelength archives of these outbursts, both photometric and spectroscopic, that show substantial outflows in the form of jets and disc winds, and X-ray spectroscopy/timing that reveals how the inner accretion disc evolves. The ground-based AAVSO optical monitoring of the MAXI J1820+070 event was the most extensive ever obtained, revealing periodic variations that evolved as it approached its state transition. These modulations were of an amplitude never seen before, and suggested the development of an irradiation-driven disc warp that persisted through the transition. All these results have demonstrated the power of extensive multi-wavelength photometric and spectroscopic monitoring on all time-scales.