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Astronomy: Mysterious bursts of extragalactic origin
The signal came from inside the Milky Way.
On April 28, scientists from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) detected a fast radio burst (FRB).
Although the detection of this type of phenomenon is very rare, it is not the first time that Canadian astrophysicists have managed to register an FRB.
The novelty in this case was its intensity: a normal burst active between two and five radio telescope antennas in British Columbia, it activated 93. With their first calculations the scientists delimited its possible origin to a region of our galaxy around the magnetar SGR 1935+ 2154.
The problem is that CHIME was not monitoring that region, so the team did not have an accurate reading to establish its absolute brightness, a key piece for the analysis.
"We immediately put a message on Astronomers Telegram to alert other telescopes around the world," recalls Daniele Michilli, an astrophysicist for the CHIME initiative.
"Fortunately the STARE2 project was observing the same signal at the same time and was able to confirm the finding."
Thus, in Utah and California, members of the Study for Transient Emission of Radio Astronomy 2 (STARE2) conducted a parallel analysis and confirmed the existence of the signal (named FRB 200428).
They also coincided with the first diagnosis of its intragalactic origin.
But, in addition, they revealed that the burst was about 1,000 times brighter than what their Canadian colleagues had initially announced.
"It is surprising that we were able to observe something like this in our galaxy, given how extremely rare these bursts are
,
"
says Christopher Bochenek, a researcher at the California Institute of Technology.
The detection of FRB 200428 is analyzed in depth in three different studies published this Wednesday in the journal
Nature
by three different groups of researchers.
These studies represent a crucial advance in understanding fast radio bursts, based on the analysis of the first FRB detected from the interior of the Milky Way.
And the
first associated with a specific magnetar
.
Enigmatic cosmic signs
The first detection of FRB dates from 2007, made thanks to the Parkes radio telescope in Australia.
Since then
its nature has intrigued astrophysicists.
These are bright bursts of radio waves, lasting about a millisecond.
The observations that have taken place over the last decade have been accompanied by multiple hypotheses to explain its origin and the underlying physics, ranging from theories that evoke possible cosmic phenomena to a supposed extraterrestrial origin.
But the mainstream of research has to do with magnetars.
A magnetar is a highly magnetized neutron star, and its powerful magnetic fields could act as the motors that drive FRBs
.
But, so far, there has been no tangible evidence linking them directly to magnetars.
Hence the importance of tracking down FRB 200428, a task that
became international detective work.
"When various international groups collaborate to study a phenomenon in different ways we learn a lot more," says Bochenek.
"In addition to radio telescopes, ray telescopes have played an important role in discovering an emission of special rays, which accompany radio bursts."
Recreation of a magnetarMcGill University Graphic Design Team
Spanish participation
Among the instruments that analyzed the sky that day in April was the Five-Hundred Aperture Spherical Telescope (FAST), in China's Guizhou province.
This extremely sensitive radio telescope had been observing SGR 1935 + 2154 in the previous weeks.
Although the Chinese scientists were unable to detect FRB 200428, they did make in-depth observations and were able to provide insight into the underlying events, specifically the presence of short bursts of gamma rays emitted by the magnetar itself.
"The fact that we have not recorded it may have to do with the spectrum or the frequency of the signal," explains Bing Zhang, a researcher at the University of Nevada-Las Vegas and responsible for the FAST collaboration.
"However, we detected another 29 small lightning emissions, which is interesting to give a general picture of the nature around the FRBs."
For this analysis, collected in another of the Nature articles, they had the collaboration of the Instituto de Astrofísica de Andalucía of the CSIC, which analyzed the magnetar region with the robotic telescopes of the BOOTES global network, including the BOOTES-2 in Malaga. .
"We observe the region, imposing limits on optical emission - even simultaneously with radio - which has resulted in a more adequate model of the magnetar environment and the underlying physical processes", explains Alberto Javier Castro-Tirado, researcher at the Instituto de Astrofísica de Andalucía (CSIC) and co-author of the third article.
The findings suggest that magnetars can produce some - perhaps all - of the fast radio bursts.
"In this specific case it has been the case, but in other FRBs the explanation is not so clear," Castro-Tirado warns.
"It is possible that they have to do with different types of objects, as it happened with the GRB (gamma ray bursts), discovered more than 50 years ago."
In the future, observations of nearby rapidly star-forming galaxies will be crucial in finding events similar to FRB 200428 and thus helping to pin down their nature.
Other magnetar-driven FRB mechanisms could produce additional physical phenomena, such as neutrino bursts.
That underlines, according to the authors, the importance of multidisciplinary astronomy: with a coordinated study of different types of signals (such as electromagnetic radiation and neutrinos) that provide all the key clues to solving this cosmic mystery.
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