One common explanation for the baffling source of the frequent radio flashes could at least go in the trash, according to Joyri van Leeuwen of Astron, the Netherlands Institute for Radio Astronomy. “It’s a puzzle,” he says.
“Fast radio bursts” were first discovered in 2007. They only last a millisecond, but in that short time as much energy is released as the Sun does in a few days. Perhaps they are explosions on so-called neutron stars: extremely compact stars less than 25 kilometers in size, but heavier than the Sun, and with a significantly strong magnetic field. Astronomers hope that research on fast radio bursts will provide more insight into nature’s most extreme form of matter.
Hundreds of such flashes have been observed since then, particularly through the relatively new Chime telescope in Canada. Most flashes are one-time, but there are also a number of frequent flashes. And one of them is called FRB20180916B (FRB stands for Radio blast), shows predictable regularity: every 16.3 days the strobe is turned on for a few days in a row; In the middle there is nothing to see.
According to Ines Pasteur-Marazuela, first author of temper natureArticle, until now it was generally believed that a blinking neutron star is accompanied by an ordinary star that orbits around it once every 16.3 days and releases a lot of gas into space. “The ‘stellar winds’ absorb the radio radiation, so that the flashes can only be seen when the normal star – which we see from our side – is behind the neutron star,” she explains.
But the new observations, made in conjunction with the dishes of the Westerbork Radio Telescope and the antennas of the Lofar telescope, cannot be explained by this model. Lofar looks at much lower frequencies than Westerbork, and you would expect these low-frequency flashes to be visible for a shorter period than those at higher frequencies, because they are more strongly absorbed. However, the opposite appears to be true. In fact, there is absolutely no evidence of gases being absorbed into the environment. “This is not true with the binary star model,” Pastor Marazuela said.
“Very perplexing,” says Victoria Caspi, who studies fast radio bursts with a resonance telescope. Kaspi also studied Lofar’s measurements of FRB20180916B, but was not involved in Westerbork’s observations. She’s not yet convinced that the idea of a binary star is completely gone, but she described the Nature publication as “a new piece in the puzzle. With the rapid bursts of radio, there are almost as many sudden fluctuations as the new results.”
cosmic speed camera
How can the normal behavior of a cosmic speed camera be explained? It may be a lone neutron star that rotates once every 16.3 days, Pasteur Marazuela says. If the flashes come from a small area on the star, we only see them if they point us in the right direction. The problem is that most neutron stars make tens, hundreds, or even a few thousand revolutions per minute. A rotation period of more than two weeks is improbably slow.
“FRB20180916B is probably a very exceptional specimen,” says Van Leeuwen. But I compare it to the work of neurologist Oliver Sacks: searching for very special patients provides a lot of general information about the human brain. Hopefully, this object will also teach us a lot about lesser-known radio flashes.”
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