First discovered by a stroke of sheer luck while combing through data from Australia’s Parkes radio telescope, the West Virginia University team that detected the first Fast Radio Burst (or FRB) had few clues as to its source.

They surmised that these high-energy, radio-luminous FRBs were likely produced by some sort of compact object. That is, either a neutron star, a white dwarf, or some sort of energetically active black hole.

Nearly two decades later, little is still known about the sources of FRBs —- except that they appear by the thousands all over the sky, mostly at vast extragalactic distances. And they are likely produced by several different astrophysical phenomena. One of the more interesting ideas is that they are the result of blitzars, the process by which a neutron star collapses into a black hole.

In a review paper just published in The Astrophysics and Space Science Journal, the authors suggest that a fast millisecond radio burst represents the final signal of a supra-massive rotating, neutron star that collapses into a black hole.

The snapping of the neutron star’s magnetic-field lines can turn an almost ordinary pulsar (a rapidly rotating, radio-emitting neutron star) into a radio-bright “blitzar,” note the authors. This produces a massive radio burst observable out to 3 billion light years away, they write.

The blitzar idea involves a neutron star being pushed over its mass limit by accreting material from some sort of stellar companion, Duncan Lorimer, the paper’s lead author and a professor of physics and astronomy at West Virginia University in Morgantown, told me via email.

The idea is that this neutron star would reach its theoretical limit so that it collapses into a stellar mass black hole. This transition, in turn, results in a massive release of energy from the neutron’s star’s magnetic field.

In the case of a blitzar, the energy contained within the neutron star’s magnetic field is released because the field can no longer be anchored to its —- now nonexistent —- stellar surface, says Lorimer.

Oppenheimer Again Ahead Of His Time

In late 1938, famed American nuclear physicist Robert J. Oppenheimer collaborated with George Volkoff, on a paper titled “On Massive Neutron Cores,” laboriously deriving their calculations from slide rules, as noted in the 2005 book, “American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer.” The two physicists suggested there was an upper limit-now called the “Oppenheimer-Volkoff limit” to the mass of these neutron stars; anything beyond this limit would become unstable.

Essentially, neutron stars exceeding a limit of two to three solar masses would become a black hole even though at the time, Oppenheimer and colleagues did not yet use that moniker. It took decades, however, before observational astronomers were able to detect such stellar mass black holes.

As for the sources of other FRBs?

In 2007, we were part of a team that discovered the so-called ‘Lorimer Burst,’ FRB 20010724, the first example of a new general class of objects now known as fast radio bursts, the authors note.

We were looking for individual radio pulses in the Magellanic Clouds that we thought might be coming from energetic pulsars, says Lorimer.

An Incredibly Bright Radio Source

It turned out to be two degrees south of the Small Magellanic Cloud and was so bright it saturated the electronics in the data acquisition system, says Lorimer. The luminosity of this pulse was inferred to be about a trillion times brighter than the brightest ones seen from pulsars, he says.

These Bursts Are Hyper Fast

There are now even some bursts seen with features on timescales of 10s of nanoseconds, says Lorimer. So far, they have been seen from 100 MHz up to about 8000 MHz in the radio band, which is where the most sensitive radio telescopes operate, he says.

FRBs As Cosmic Probes

One of the amazing aspects of FRB studies is that they act as probes of intervening matter, even if one does not fully understand their source populations, all that is needed is a sample of FRBs with well-determined redshifts, the authors write. From this, it is possible to effectively count the number of electrons along different sight lines in the Universe and measure the electron density directly, they note.

About ten percent of all FRBs repeat.

This means that at least some FRBs come from persistent sources (such as flares on neutron stars), rather than some one-off cataclysmic origin (such as mergers of neutron stars), says Lorimer.

The Bottom Line?

Understanding the sources of FRBs is crucial to making sense of stellar evolution and the end states of stars in general, says Lorimer. As we unravel their mysteries, it’s a good bet that compact objects (white dwarfs, neutron stars and black holes) will be involved in all of this, he says.