Using the Lovell Telescope, an international team led by Jodrell Bank Observatory discovered 32 fast radio bursts (FRBs), among the most enigmatic and powerful events in the cosmos, initially thought to be one-off events over a four-year study, revealing the presence of a regular sequence in the burst activity could imply that the powerful bursts are linked to the orbital motion of a massive star, a neutron star or a black hole. The emission from the FRB, known as 121102, follows a cyclic pattern, with radio bursts observed in a window lasting approximately 90 days followed by a silent period of 67 days. The same behavior then repeats every 157 days.
“This is an exciting result as it is only the second system where we believe we see this modulation in burst activity. Detecting a periodicity provides an important constraint on the origin of the bursts and the activity cycles could argue against a precessing neutron star,” said Dr. Kaustubh Rajwade of The University of Manchester, who led the new research.
In a 2018 study, Harvard astrophysicist Avi Loeb examined the possibility that fast radio bursts come from radio transmitters constructed by an advanced alien civilization — perhaps evidence of powerful energy beams used to propel alien starships based on the hypothesis that repeater sources are more likely to be alien signals because natural origin explanations would most likely produce only a single burst. “We still have no new clue on whether the origin is artificial or natural,” observed Loeb.
“Fast radio bursts are exceedingly bright given their short duration and origin at great distances, and we haven’t identified a possible natural source with any confidence,” added Loeb. “An artificial origin is worth contemplating and checking.”
The Jodrell Bank team reported that although repeating FRBs could be explained by the precession, like a wobbling top, of the magnetic axis of a highly magnetized neutron star, but with current data scientists believe it would be hard to explain a 157-day precession period given the large magnetic fields expected in these stars.
The existence of FRBs was only discovered as recently as 2007, and were initially related to a cataclysmic event such as an exploding star. This picture partly changed once FRB 121102, originally discovered with the Arecibo radio telescope on November 2 2012, was seen to repeat in 2016. However, until now, no one recognized that these bursts were in fact organised in a regular pattern.
“This result relied on the regular monitoring possible with the Lovell Telescope, and non-detections were just as important as the detections,” said Benjamin Stappers, who leads the MeerTRAP project to hunt for FRBs using the MeerKAT telescope in South Africa.
In a new paper published in Monthly Notices of the Royal Astronomical Society, the team confirm that FRB 121102 is only the second repeating source of FRBs to display such periodic activity. To their surprise, the timescale for this cycle is almost 10 times longer than the 16-day periodicity exhibited by the first repeating source, FRB 180916.J10158+56, which was recently discovered by the CHIME telescope in Canada.
“This exciting discovery highlights how little we know about the origin of FRBs,” says Duncan Lorimer who serves as Associate Dean for Research at West Virginia University and, along with Ph.D. student Devansh Agarwal, helped develop the data analysis technique that led to the discovery. “Further observations of a larger number of FRBs will be needed in order to obtain a clearer picture about these periodic sources and elucidate their origin,” he added.
The Daily Galaxy, Max Goldberg, via University of Manchester
Image credit: Artist’s conception of the localization of Fast Radio Burst 180916.J0158+65 to its host galaxy, based on real observations using the Gemini-North telescope atop Mauna Kea in Hawaii. The burst emanating from the galaxy is based on real data recorded using the 100-meter Effelsberg radio telescope in Germany. With thanks to Danielle Futselaar (artsource.nl)