(ORDO NEWS) — The dead star, 14,350 light years away, has become the most important clue in unraveling the secret of the fast radio signal.
Earlier this year, it emitted a colossal millisecond radio signal – and now the first published analysis of the event notes its resemblance to mysterious extragalactic signals.
Fast radio bursts (FRBs) are a mystery that has puzzled astronomers since the first were discovered in 2007. They are bursts of extremely intense radio waves from galaxies millions of light years away, with some emitting more energy than hundreds of millions of suns. But only a millisecond duration.
Since most of the FRBs found to date are one-off, non-recurring events that occur very far away and cannot be predicted, they have proven extremely difficult to track and therefore study. The proposed explanations have ranged from supernovae to aliens (highly unlikely), but one source candidate has shown a growing prospect: magnetars.
In a case earlier this year, a magnetar called SGR 1935 + 2154 was discovered that was emitting bursts of millisecond radio waves.
“This is the first observational link between magnetars and fast radio bursts,” said astrophysicist Sandro Mereghetti of the National Institute of Astrophysics in Italy.
“This is a really important discovery that helps focus attention on the origin of these mysterious phenomena.”
Magnetars are a type of neutron star – the dead remnant of a massive star after it exploded most of its mass in a supernova – with extremely powerful magnetic fields 1,000 times more powerful than normal neutron stars.
These powerful magnetic fields have a strange effect. As gravity applies an internal force to hold the star together, the magnetic field pulls outward, distorting the star’s shape.
These two competing forces create tension that sometimes leads to the release of energy. They are called magnetic flares, and they usually produce X-rays and gamma rays. Only very rarely do magnetars emit radio waves.
Therefore, when SGR 1935 + 2154 was detected at the end of April, monitoring devices around the world turned in its direction.
Initially it looked like a fairly standard magnetar flash, but on April 28th there was an unprecedented flash: a very bright burst of radio emission that looked strikingly similar to the fast radio signal detected by multiple instruments.
The radio signal was so powerful that the transient detection telescope of the Canada Hydrogen Intensity Mapping Experiment (CHIME), which is responsible for detecting large amounts of FRBs, could not quantify it.
Not because the flare was more powerful than the extragalactic radio bursts (in fact, it was weaker), but because it was much closer.
Using data collected by the European Space Agency’s INTEGRAL satellite, Mereghetti and his team linked the signal to a magnetar, analyzed and characterized it.
“It is important to note that the IBIS scanner at Integral allowed us to pinpoint the origin of the flare and record its relationship with the magnetar,” said astrophysicist Vladimir Savchenko of the University of Geneva in Switzerland.
Although the flare itself was slightly weaker than the extragalactic FRBs, almost everything else in it corresponds to the extragalactic profile of fast radio bursts. But there was also a surprise – the signal had an X-ray analogue, which we have never seen in the extragalactic FRB.
This does not mean that extragalactic FRBs have no X-ray counterparts; in fact, it could mean the opposite, that the signals are more complex than we thought, spewing out many types of radiation that we cannot yet detect.
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