Ejection of the corona at State transitions: a common behaviour in microquasars?

TL;DR

This paper reviews evidence from multiple microquasars suggesting that the corona is ejected during state transitions, highlighting a potentially common behavior that links spectral changes with radio ejections.

Contribution

It synthesizes observational data indicating corona ejection at state transitions across several microquasars, proposing a common physical mechanism.

Findings

Coronal flux decreases sharply before radio ejections.

Physical changes in the corona occur before state transitions.

Ejection of the corona may be a universal feature in microquasars.

Abstract

The onset of most microquasar outbursts is characterized by a state transition between a Low/Hard State (LHS) and a High/Soft State (HSS). Besides drastic spectral and timing changes, this transition often shows a discrete ejection event detectable in the radio range. However, the exact nature of the ejected material and the mechanisms that give birth to these phenomena are yet to be unraveled. Recent simultaneous radio and X-ray observations on several sources point to a coronal nature of the ejected material. In the cases of GRS 1915+105, XTE J1550-564, and the 2002 outburst of GX 339-4, the flux of the Compton component decreases sharply just before an ejection is detected in the radio range. Finally, in the case of H1743-322, drastic physical changes occurred in the corona just before the state transition, compatible with the disappearance of part of this medium. Thus, the behaviour of at least 4 microquasars points in the direction of an ejection of the corona at the state transition, feature that is yet to be confirmed (or infirmed) in the case of other available sources.