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A Milky Way magnetar named SGR 1935 + 2154 may have contributed enormously to solving the mystery of the powerful deep space radio signals that have bothered astronomers for years.
On April 28, 2020, the dead star, which is only 30,000 light-years away, was recorded by radio observatories around the world, seemingly ablaze with a single blast of incredibly bright millisecond-long radio waves that they could have been detected from another galaxy.
Furthermore, global and space X-ray observatories recorded a very bright X-ray counterpart.
Work on this event is highly preliminary, with astronomers struggling madly to analyze the data strips. But many seem to agree that it could finally point to the source of fast radio bursts (FRB).
“This, in the minds of most people, states that the origin of FRBs comes from magnetars,” Caltech astronomer Shrinivas Kulkarni and a member of one of the teams, the STARE2 survey that also detected the signal, told ScienceAlert radio.
Rapid radio bursts are one of the most fascinating mysteries in the cosmos. They are extremely powerful radio signals from deep space, galaxies millions of light years away, some that discharge more energy than 500 million suns. However, they last less than the blink of an eye, only milliseconds in duration, and most of them are not repeated, making them very difficult to predict, track, and therefore understand.
Possible explanations range from supernovae to aliens (which, I’m sorry, is extremely unlikely). But one possibility that has been gaining strength is that FRBs are produced by magnetars.
These are a particularly strange type of neutron star, the extremely dense core debris that remains after a massive star turns into a supernova. But magnetars have much more powerful magnetic fields than ordinary neutron stars, about 1,000 times stronger. How they got that way is something we don’t quite understand, but it has an interesting effect on the star itself.
As the gravitational force tries to hold the star together, an internal force, the magnetic field is so powerful that it distorts the shape of the star. This leads to continuous tension between the two forces, explained Kulkarni, which occasionally produces gigantic stellar earthquakes and flashes of giant magnetar.
On April 27, 2020, SGR 1935 + 2154 was detected and observed by multiple instruments experiencing an outbreak of activity, including the Swift Burst Alert telescope, AGILE satellite, and NICER ISS payload. Initially it seemed relatively normal, consistent with the behavior observed in other magnetars.
But then on April 28, the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a telescope designed to scan the skies for transient events, performed an unprecedented detection, a signal so powerful that the system was unable to quantify it. . The detection was reported in The Astronomer’s Telegram.
But the STARE2 survey, a project started by Caltech graduate student Christopher Bochenek, is designed exactly for the detection of local FRBs. It consists of three dipole radio antennas located hundreds of kilometers away, which can firstly rule out local signals produced by human activities, and can also allow signal triangulation.
It received the signal loud and clear, with a creep of over a million Jansky milliseconds. Typically, we receive extragalactic FRBs within a few tens of jansky milliseconds. Once corrected for distance, the SGR 1935 + 2154 would be at the low end of the FRB stem, but it fits the profile, Kulkarni said.
“If the same signal came from a nearby galaxy, like one of the typical nearby FRB galaxies, it would look like an FRB to us,” he told ScienceAlert. “Something like this has never been seen before.”
Transient phase space chart now with lower limit SGR 1935 + 2154 of STARE2. I think the interpretation is written alone. pic.twitter.com/8ScrlcyqLW
– A Dr. Evan Ó Catháin🅾️ (@evanocathain) April 29, 2020
But we also saw something else we’ve never seen on an extragalactic FRB, and that’s the X-ray counterpart. These are quite common in magnetar outbursts, of course. In fact, it is much more normal for magnetars to emit X-rays and gamma radiation than radio waves.
The X-ray counterpart of the SGR 1935 + 2154 explosion was not particularly strong or unusual, said astrophysicist Sandro Mereghetti of the National Institute of Astrophysics in Italy, which processes the data for the X-ray satellite AGILE. But it could imply that FRBs have much more than we can currently detect.
“This is a very intriguing result and supports the association between FRB and magnetars,” Mereghetti told ScienceAlert.
“The FRBs identified so far are extragalactic. They have never been detected on X-ray / gamma rays. An X-ray burst with a luminosity like that of SGR1935 would be undetectable for an extragalactic source.”
But that radio signal was undeniable. And, according to Kulkarni, it is absolutely possible for a magnetar to produce even greater outbursts. The SGR 1935 + 2154 burst did not require much energy, to be a magnetar, and the star could easily handle a burst a thousand times stronger.
They are certainly dizzying things. But it is important to note that this is still early. Astronomers continue to make follow-up observations of the star using some of the most powerful tools we have.
And they still have to analyze the spectrum of the explosion, to determine if it has any similarity to the spectrum of extragalactic fast radio bursts. If not, we can return to the starting point.
Of course, even if SGR 1935 + 2154 turns out to confirm a magnetar origin for fast radio bursts, that doesn’t mean it’s the only origin. Some of the signals behave very differently, repeating themselves unpredictably. It was recently discovered that a source repeats itself on a 16-day cycle.
Regardless of what SGR 1935 + 2154 tells us, we are far from completely solving the complicated puzzle that these incredible signs represent, but it is an incredibly exciting step.
CHIME has yet to respond to ScienceAlert’s request for an interview. They were probably too busy.
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