Researchers have again found evidence that the extremely short flashes in space are caused by magnetars.
It has been suspected that fast radio bursts are caused by magnetars. And was further reinforced earlier this year when researchers spotting a radio flash in our own Milky Way for the first time from the magnetar SGR 1935 + 2154. An important discovery. But with a single flash proven to be from a magnetar, the evidence for the above hypothesis remained thin. And so, Dutch and Swedish researchers decided to join forces and hunt for more evidence. They aimed radio telescopes in the Netherlands, Sweden and Poland at SGR 1935 + 2154, hoping to witness it again producing fast radio bursts. And they were lucky!
Two flashes
Because on May 24, the researchers caught two fast radio bursts, each lasting only a millisecond and successive after 1.4 seconds. “We clearly saw two flashes, which were extremely close together,” says researcher Kenzie Nimmo, associated with the Anton Pannekoek Institute for Astronomy and ASTRON. The flashes were somewhat fainter than the radio bursts that researchers have seen from this magnetar before.
About fast radio bursts and magnetars
Fast radio bursts have occupied astronomers for about a decade. The very bright, but extremely short-lived flashes initially seemed to originate only from galaxies billions of light years away. And that made it difficult to determine exactly how the flashes came about. But earlier this year, a fast radio flash was first detected in our Milky Way. And it turned out to come from the magnetar SGR 1935 + 2154.
A magnetar is a fairly rare type of neutron star: a super-compact remnant of exploded massive stars. A neutron star rotates quickly, has a strong magnetic field and a diameter of about 20 kilometers, but a mass larger than the sun. Magnetars are young neutron stars with an exceptionally powerful magnetic field. They are quite rare: only a few dozen of them have been discovered to date. The existence of magnetar SGR 1935 + 2154 was revealed six years ago and represents one of the few magnetars in our Milky Way. SGR 1935 + 2154 is located near the center of the Milky Way and is about 30,000 light-years away from Earth.
“Like the remote strobes, SGR 1935 + 2154 seems to flash randomly and with great variation in brightness. The brightest flashes from this magnetar are at least ten million times as bright as the least bright eruptions, ”says researcher Mark Snelders, also associated with the Anton Pannekoek Institute.
“We expect new measurements and surprises in the coming months and years”
Disturbance in the magnetosphere
Astronomers have been puzzled over how fast radio bursts can occur for years. Research into the origin of the flashes is gaining momentum due to recent observations. For example, researchers already have concrete ideas about how nearby magnetars can generate the fast radio bursts. “The eruptions we saw on May 24 may be the result of a dramatic disruption in the star’s magnetosphere, which is occurring close to the surface,” said researcher Franz Kirsten, associated with it. Onsala Space Observatory. Other explanations, such as shock waves further away from the magnetar, seem less unlikely. Kirsten predicts that there will soon be more clarity about the processes that lead to the formation of the fast radio bursts. “We expect new measurements and surprises in the coming months and years.”
Further away
The observations in our own Milky Way also have implications for fast radio bursts that have previously been spotted outside our galaxy, says Jason Hessels, affiliated with ASTRON and the University of Amsterdam. “We now suspect that the fast radio bursts outside our own galaxy are also caused by magnetars. If so, the magnetars create radio waves that constantly zigzag through the universe. And the great thing is that many of these waves are within reach of modest-sized telescopes, like ours. ”
Repetitive and non-repetitive
As mentioned before, quite a few fast radio bursts have also been spotted outside our galaxy. Some of these fast radio bursts have only been seen once. Others – such as the fast radio bursts that were spotted in our own galaxy in May – repeatedly make an appearance. That is why it is also said that fast radio bursts come in two flavors: repetitive and non-repetitive. The big question, however, is whether non-repeating radio bursts actually exist. After all, it is also possible that all radio flashes repeat, but sometimes do so at long intervals, so that we do not notice this. Or that not all fast radio bursts from the same source are equally bright and we can only observe the brightest with our telescopes. “Recent results indicate that magnetars are the source of fast radio bursts,” Nimmo tells Scientias.nl. “This follows from the detection of a bright radio flash from SGR 1935 + 2154. What we have discovered are two fainter radio bursts from the same source. ” It shows that magnetars can generate a wide variety of radio bursts: some are quite faint, some are exceptionally bright. Because 1935 + 2154 is relatively close, researchers are able to spot both those bright and fainter radio bursts. But had it been a bit further away, chances are that we would have been able to detect only the brightest flash. “And then it would have seemed like a non-repetitive high-speed radio flash,” Nimmo said. “Magnetars such as SGR 1935 + 2154 may also rarely produce these very bright fast radio bursts and fast radio bursts outside our galaxy are therefore often described as ‘non-repetitive’. Follow-up research should provide more clarity about this.
All in all, there is still plenty to research. “We will continue to monitor SGR 1935 + 2154 and other magnetars to find out how rare these events really are.” In this way, more clarity must also be obtained about how the special neutron stars exactly generate the radio bursts.
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