V404 Cyg: The Kraken Wakes

After 26 years dormant, the nearby black hole V404 Cyg went into outburst on Monday last week (June 15). Many of the world’s premier observatories are following this spectacular outburst, which is likely to yield the textbook event for black hole accretion for many years to come.

The 4 PI SKY team are at the forefront of efforts to collect data and understand this source. Most notably, the AMI-LA telescope in rapid response mode (ALARRM), was triggered by a Swift X-ray alert on the source and obtained radio data only two hours after the trigger, revealing already a bright and declining radio flare (see figure below).


Since this initial observation we have been following the source intensely with AMI and have detected a large number of radio flares, which are probably associated with relativistic ejection events. 4 PI SKY team members are also involved in radio observations with other major facilities such as eMERLIN and LOFAR, and are leading aspects of the X-ray and optical data analysis.

The ALARRM robotic observations of V404 were reported in this press release from the European Space Agency:

ESA press release on V404 Cyg