Lasting only a fraction of a second yet packing a phenomenal amount of energy, FRBs are brief radio flashes of unknown origin that appear to come from random directions on the sky. Though only a handful have been documented previously, astronomers believe that the observable Universe is rocked by thousands of these events each day."

Source : National Radio Astronomy Observatory, US

The bursts typically last only a few milliseconds, are wideband (from MHz to GHz), sometimes polarised, and are thought to originate predominantly outside our galaxy. Possible explanations for their source include:

• Collapsing black holes or neutron stars
• Blitzars (a spinning pulsar rapidly collapses into a black hole)
• Hyperflares of magnetars (a neutron star with an extremely powerful magnetic field)

However :

None of the models put forward seem perfectly adequate. Not one really explains all the observations.”

Source; PNAS 2017

More info Max Planck Institute for Radio Astronomy

Note: A 2017 study from Harvard put forward the imaginative idea that FRBs may be signs of Alien Civilisation's use of photon-drives to propel their spacecraft . . . though the authors end with the statement that the purpose of their paper includes "at the very least, the important purpose of enabling astronomers to rule it out" . . . See : Fast Radio Bursts from Extragalactic Light Sails

Project Breakthrough Listen (UC Berkeley)

[…] has detected 15 fast radio bursts emanating from the mysterious 'repeater' FRB 121102."

Source

Also see Fast Blue Optical Transientsplugin-autotooltip__plain plugin-autotooltip_bigFast Blue Optical Transients

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 vastly more powerful.

A research team from Northwestern University, US, have recently calculated that the events appear to be able to expel a mass of 1% > 10% of the mass of the Sun at a velocity of