Transient Relativistic Ejections and Stationary Core in XTE J1752-223

TL;DR

This paper reports on the detection of transient and stationary radio components in XTE J1752-223, revealing highly relativistic ejecta, deceleration, and core reappearance during state transitions, advancing understanding of black hole binary jets.

Contribution

It presents new VLBI observations showing transient ejecta, a stationary core component, and evidence of decelerating relativistic jets in XTE J1752-223, with re-analysis of earlier data for comprehensive insights.

Findings

Detection of transient and decelerating ejecta with high proper motion

Identification of a stationary core component during state transition

Evidence of mildly relativistic ejecta at early stages

Abstract

The Galactic X-ray transient XTE J1752-223 was shown to have properties of black hole binary candidates. As reported in our previous paper, we identified transient and decelerating ejecta in multi-epoch Very Long Baseline Interferometry (VLBI) observations with the European VLBI Network (EVN) and the NRAO Very Long Baseline Array (VLBA). Here we present new EVN and VLBA data in which a new transient ejection event and later a stationary component are identified. The latter is interpreted as a reappearance of the radio core/compact jet during the transition from soft to hard X-ray state. This component appears to be highly variable in brightness although effects of tropospheric instabilities might play a role too. We also re-analyze the earlier VLBI data and find that the transient ejecta closer to the core position has significantly higher proper motion, further strengthening the case for strongly decelerating ejecta on the scale of several hundred milli-arcsecond, never observed in X-ray binaries before. Although the distance of the source is not well constrained, it is clear that these ejectas are at least mildly relativistic at the early stages. Moreover, we show the large scale environment of the transient from the Westerbork synthesis array data recorded in parallel during the EVN run.