XTE J1752-223 in outburst: a persistent radio jet, dramatic flaring, multiple ejections and linear polarisation

TL;DR

This study presents a detailed radio and X-ray analysis of the black hole candidate XTE J1752-223 during its 2009 outburst, revealing persistent jets, multiple ejections, and complex flaring behavior with implications for jet physics.

Contribution

It provides the first comprehensive radio monitoring over the entire outburst, identifying multiple ejections, superluminal motion, and interactions with the environment, advancing understanding of jet mechanisms in black hole transients.

Findings

Persistent radio jet during the entire hard state

At least 7 radio flares with similar energy requirements

Evidence of superluminal ejecta and jet-environment interactions

Abstract

The black hole candidate, XTE J1752-223, was discovered in 2009 October when it entered an outburst. We obtained radio data from the Australia Telescope Compact Array for the duration of the ~9 month event. The lightcurves show that the radio emission from the compact jet persisted for the duration of an extended hard state and through the transition to the intermediate state. The flux then rose rapidly by a factor of 10 and the radio source entered a series of at least 7 maxima, the first of which was likely to be emission associated with the compact jet. The subsequent 6 flares were accompanied by variable behaviour in terms of radio spectrum, degree of linear polarisation, morphology and associated X-ray behaviour. They were, however, remarkably similar in terms of the estimated minimum power required to launch such an ejection event. We compare the timing of radio peaks with the location of the ejecta, imaged by contemporaneous VLBI experiments. We then discuss the mechanism behind the events, in terms of whether discrete ejections is the most likely description of the behaviour. One ejection, at least, appears to be travelling with apparent superluminal motion. The range of properties, however, suggests that mutiple mechanisms may be relevant and that at least some of the emission is coming from shocked interactions amongst the ejecta and between the ejecta and the interstellar medium. We also compare the radio flux density with the X-ray source during the hard state and conclude that XTE J1752-223 is a radio-weak/X-ray-bright outlier on the universal correlation for black hole transient sources.