The Australian Square Kilometre Array Pathfinder telescope has been used to track the endlessly puzzling Fast Radio Bursts (FRBs) to their host galaxies. These events are extremely powerful and extremely quick emissions of radio waves; the same amount of energy the Sun emits in a day but in just a fraction of a second.
The source of these events remains unclear. They can't be predicted, and because they flash so quickly, they are hard to trace. But since the first repeating FRB was traced back to its host galaxy in early 2018, researchers have been able to trace three more events back to their host galaxies, which has allowed us to gain more insights into what might be creating the FRBs.
As reported in The Astrophysical Journal Letters, the team studied where FRB 180924, FRB 181112, FRB 190102, and FRB 19060 come from. A very precise position was only possible for two of them but all four signals allowed researchers to establish some important constraints to what the source of FRBs are not, meaning we can rule them out and hopefully narrow down what they may be.
The data suggest that these cosmic emissions are not due to supermassive black holes at the core of galaxies. They are also unlikely to be caused by very powerful supernovae as these are hardly found in massive galaxies such as the hosts of these four FRBs. The team also excludes more outlandish explanations like cosmic strings, hypothetical and peculiar relics of events that happened a fraction of a second after the Big Bang.
“Just like doing video calls with colleagues shows you their homes and gives you a bit of an insight into their lives, looking into the host galaxies of fast radio bursts gives us insights to their origins,” lead author Dr Shivani Bhandari, an astronomer with the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO), said in a statement. “These precisely localized fast radio bursts came from the outskirts of their home galaxies, removing the possibility that they have anything to do with supermassive black holes.”
Many candidate hypotheses are still in the running. From the collision of dense objects such as white dwarfs or neutron stars to flares released by magnetars, a type of pulsating neutron star (pulsar) that have an obscenely large magnetic field.
The more FRBs are tracked back to their cosmic neighborhood, the better we’ll be able to constrain their possible origin.
“Major advances for other transient events have been made by studying their home galaxies. We are optimistic that studies like ours will be just as vital,” added co-author Dr Xavier Prochaska of the University of California, Santa Cruz, who co-led the optical observations.
The work even earned the praise of Dame Dr Jocelyn Bell Burnell, who discovered the first rapidly spinning neutron star, now known as "pulsars," when she was a postgraduate student.
“Positioning the sources of fast radio bursts is a huge technical achievement, and moves the field on enormously,” Dr Bell Burnell said. “We may not yet be clear exactly what is going on, but now, at last, options are being ruled out. This is a highly significant paper, thoroughly researched, and well written.”