A fast radio burst (FRB) called FRB 20191221A persists for up to three seconds, about 1,000 times longer than the average FRB; within this window, CHIME / FRB collaboration astronomers detected bursts that are repeated every 217 ms in a clear periodic pattern, resembling a beating heart.
The plates distributed worldwide in the European VLBI network are connected to each other and to the 305 m William E. Gordon Telescope at the Arecibo Observatory in Puerto Rico. Together they have located the exact position of FRB121102 within their host galaxy. Image credit: Danielle Futselaar, www.artsource.nl.
FRBs are millisecond-length radio wave flashes that are visible at distances of billions of light-years and exhibit the scattering sweep characteristic of radio pulsars.
These events emit as much energy in a millisecond as the Sun emits in 10,000 years, but the physical phenomenon that causes them is unknown.
Theories range from highly magnetized neutron stars, launched by gas currents near a supermassive black hole, to suggestions that the properties of the explosion are consistent with the signatures of technology developed by an advanced civilization.
The vast majority of FRBs observed so far are punctual; but recently, astronomers discovered FRB 180916.J0158 + 65, the first periodic FRB that appeared to emit a regular pattern of radio waves.
This signal consisted of a four-day window of random bursts that were then repeated every 16 days.
The 16-day cycle indicated a periodic pattern of activity, although the signal from the actual radio bursts was random rather than periodic.
On December 21, 2019, astronomers from the CHIME / FRB Collaboration picked up a signal of a potential FRB.
“FRB 20191221A was unusual,” said Dr. Daniele Michilli, an astronomer at MIT’s Kavli Institute for Astrophysics and Space Research.
“Not only was it very long, it lasted about three seconds, but there were periodic peaks that were remarkably accurate, emitting every fraction of a second like a heartbeat.”
“This is the first time the signal itself is periodic.”
Cascading graph of FRB 20191221A radio signal strength as a function of time and frequency. Image credit: Andersen et al., Doi: 10.1038 / s41586-022-04841-8.
In analyzing the burst pattern of FRB 20191221A, Dr. Michilli and colleagues found similarities with radio pulsar and magnetar emissions in our own galaxy.
“Radio pulsars are neutron stars that emit beams of radio waves, which appear to pulsate as the star rotates, while magnets produce a similar emission because of their extreme magnetic fields,” they said.
“The main difference between the new signal and the radio emissions of our own galactic pulsars and magnets is that FRB 20191221A appears to be more than a million times brighter.”
“Luminous flashes can originate from a pulsar or magnet from a distant radio that is usually less bright as it rotates and, for some unknown reason, ejected a train of bright bursts, in a rare window of three according to which CHIME was fortunately positioned to catch “.
Astronomers hope to capture additional bursts of the FRB 20191221A newspaper, which may help perfect their understanding of its source and neutron stars in general.
“This detection raises the question of what could cause this extreme signal that we had never seen before and how we can use this signal to study the Universe,” Dr. Michilli said.
“Future telescopes promise to discover thousands of FRBs a month, and right now we can find many more of these periodic signals.”
The findings were published in the journal Nature.
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BC Andersen et al. (CHIME / FRB collaboration). 2022. Frequency less than the second on a fast radio. Natura 607, 256-259; doi: 10.1038 / s41586-022-04841-8