Correlated radio--X-ray variability of Galactic Black Holes: A radio--X-ray flare in Cygnus X-1

TL;DR

This paper reports the first quasi-simultaneous radio and X-ray flare detection in Cygnus X-1, revealing a 7-minute lag that offers insights into jet ejection processes during state transitions.

Contribution

It presents the first observation of a near-simultaneous radio-X-ray flare in Cygnus X-1, highlighting the timing and potential physical mechanisms involved.

Findings

Radio flare lagged X-rays by approximately 7 minutes

Detected during a soft-to-hard state transition

Supports models of electron bubble ejections in jets

Abstract

We report on the first detection of a quasi-simultaneous radio-X-ray flare of Cygnus X-1. The detection was made on 2005 April 16 with pointed observations by the Rossi X-ray Timing Explorer and the Ryle telescope, during a phase where the black hole candidate was close to a transition from the its soft into its hard state. The radio flare lagged the X-rays by approximately 7 minutes, peaking at 3:20 hours barycentric time (TDB 2453476.63864). We discuss this lag in the context of models explaining such flaring events as the ejection of electron bubbles emitting synchrotron radiation.