Astronomers using the Australian SKA Pathfinder (ASKAP) telescope at CSIRO’s Murchison Radio-astronomy Observatory have tracked four mysterious blasts of cosmic radio waves back to their home galaxies; all four came from the outer regions of massive galaxies with moderate star-formation rates, ruling out central supermassive black holes and cosmic strings as a source.
Fast radio bursts (FRBs) are enigmatic and rarely detected bursts of energy that come from far beyond our Milky Way Galaxy.
Lasting several milliseconds, they were first detected at the Parkes radio telescope by Australian astronomers Duncan Lorimer and David Narkevic in 2007.
Scientists estimate that there are between 2,000 and 10,000 FRBs occurring in the sky every day.
They emit as much energy in one millisecond as the Sun emits in 10,000 years, but the processes that cause them are unknown.
Using a specially designed transient detector on ASKAP, CSIRO astronomer Shivani Bhandari and colleagues found the exact location of four new fast radio bursts: FRB 180924, FRB 181112, FRB 190102 and FRB 190608.
Follow-up observations with the Gemini South, ESO’s Very Large Telescope, Magellan Baade, Keck, and LCOGT-1m telescopes imaged and found the distances to the host galaxies.
“Major advances for other transient events have been made by studying their home galaxies,” said Dr. J. Xavier Prochaska, an astronomer at the University of California, Santa Cruz.
“We are optimistic that studies like ours will be just as vital.”
The astronomers found FRB 180924, FRB 181112, FRB 190102 and FRB 190608 came from massive galaxies that are forming new stars at a modest rate, very similar to the Milky Way.
All four new FRBs lie in the outskirts of their galaxies, which appears to rule out the progenitor models that involve active galactic nuclei (i.e. accreting supermassive black holes located in the center of galaxies) or free-floating cosmic strings.
“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,” Dr. Bhandari said.
“These fast radio bursts could not have come from a superluminous stellar explosion, or from cosmic strings,” said CSIRO’s Professor Elaine Sadler.
“Models such as mergers of compact objects like white dwarfs or neutron stars, or flares from magnetars created by such mergers, are still looking good.”
“Positioning the sources of fast radio bursts is a huge technical achievement, and moves the field on enormously,” said Dr. Dame Jocelyn Bell Burnell, an astrophysicist from Northern Ireland who co-discovered the first radio pulsars in 1967.
“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.”
The findings were published in the Astrophysical Journal Letters.