Fast Blue Optical Transients (FBOTs) are a recently discovered (2014) class of transient astronomical objects. They have similarities with Gamma-ray bursts - but appear to be far more powerful.
A recent observation by a team from Northwestern University, US have calculated that the events can expel a mass of 1% > 10% of the mass of the Sun at a velocity of 55% light speed.
There is currently no explanation of how this might happen,
See: news release , Northwestern, May 2020.