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Astronomers detected two more millisecond radio bursts from SGR 1935 + 2154, a magnetar located over 14,000 light-years away in the constellation of Vulpecula. The detection supports the hypothesis that – at least some – fast radio bursts are emitted by magnetars at cosmological distances.
On May 24, 2020, four European radio telescopes detected two bright radio bursts from the magnetar SGR 1935 + 2154. Image credit: Danielle Futselaar / Artsource.nl.
Fast radio bursts (FRBs) are mysterious and rarely detected bursts of radio waves from space.
These events last for milliseconds and show the characteristic scattering sweep of radio pulsars.
They emit as much energy in a millisecond as the Sun emits in 10,000 years, but the physical phenomenon that causes them is unknown.
One theory speculated that FRBs were neutron stars with exceptionally strong magnetic fields, commonly known as magnetars.
On April 28, 2020, a breakthrough was made when two teams of astronomers independently detected an extremely bright radio blast from the galactic magnetar SGR 1935 + 2154, using the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME / FRB) and the Survey for Transient Astronomical Radio Emission 2 (STARE2) respectively.
The specific energy of the burst, dubbed FRB 200428, was similar, although about 30 times lower, to the specific energy of the weakest known FRB.
In May 2020, a research team led by astronomer Franz Kirsten of Chalmers University of Technology pointed to four radio telescopes towards SGR 1935 + 2154.
“We didn’t know what to expect,” said team member Dr. Mark Snelders, an astronomer from the Anton Pannekoek Institute of Astronomy of the University of Amsterdam.
“Our radio telescopes have only rarely been able to see fast radio bursts and this source seemed to do something completely new. We were hoping to be surprised! “
Astronomers monitored SGR 1935 + 2154 every night for more than four weeks after the discovery of FRB 200428, for a total of 522 hours of observation.
On May 24, they detected two bright radio bursts with fluences of 112 ms and 24 ms, respectively, but separated in the time of 1.4 s.
“We clearly saw two bursts, extremely close in time,” said team member Dr. Kenzie Nimmo, an astronomer at the Anton Pannekoek Institute for Astronomy and ASTRON.
“Like the flash seen from the same source on April 28, this one looked just like the fast radio bursts we were seeing from the distant Universe, only fainter. The two explosions we detected on May 24 were even weaker than that. “
Together with the burst FRB 200428, as well as a much weaker burst as seen by the FAST radio telescope, the new observations show that SGR 1935 + 2154 can produce bursts with apparent energies that span about seven orders of magnitude and that the burst speed is comparable. in this interval.
“The brightest flashes of this magnetar are at least 10 million times brighter than the faintest ones,” said team member Dr. Jason Hessels, astronomer at the Anton Pannekoek Institute for Astronomy and ASTRON.
“We asked ourselves, could this also be true for fast radio burst sources outside our Galaxy?”
“If so, then the Universe’s magnetars are creating beams of radio waves that could cross the cosmos all the time – and many of these could be within the reach of modest-sized telescopes like ours.”
The results were published in the journal Nature Astronomy.
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F. Kirsten et al. Detection of two bright radio flashes from the magnetar SGR 1935 + 2154. Nat Astron, published online November 16, 2020; doi: 10.1038 / s41550-020-01246-3
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