The researchers are wondering about its source... a fast radio burst repeated over two months
A new recurring fast radio burst incident is making researchers interested in working again, as scientists have detected a strange, very ancient signal from the depths of space.
In 2021, a repeating signal was picked up in a phenomenon called a fast radio burst (FRB) from a very distant source. The scientists recorded 1,863 streams within 82 hours of a total of 91 hours of observation.
This hyperactive behavior allowed the scientists to determine the properties and distance of the galaxy containing the source of the jet, and to understand the nature of the source itself.
The Spherical Radio Telescope (FAST) in China spotted this object, which astronomer Heng Xu of Peking University described in a new paper and named it (FRB 20201124A).
Based on available evidence, scientists believe that the source of such a fast radio burst is most likely a magnetar, a neutron star with very strong magnetic fields.
If FRB 20201124A is indeed one such massive cosmic body, it appears to be strikingly unique.
“These observations made us search again,” says astrophysicist Peng Zhang of the University of Nevada, Las Vegas. It is clear that the phenomenon of fast radio bursts is much more mysterious than we imagined. We need more monitoring campaigns at multiple wavelengths to know more about the nature of these objects.”
Fast radio bursts have always baffled astronomers since their discovery 15 years ago in archived data dating back to 2001, when they detected a very sharp rise from a very powerful fast radio burst that lasted only for a moment before it disappeared.
Since then, many more have been discovered: transmissions of radio waves that last for fractions of a second, emitting super-energy 500 million times that of the sun.
Most of these observations were single, infrequent emissions, which made them difficult to study and understand, given the lack of clear patterns. But very few of them have been spotted repeating, which has helped scientists trace them back to the galaxies from which they emanate.
Then, in the year 2020, an important development occurred, as a fast radio flux was detected in the Milky Way galaxy for the first time, and this made scientists investigate the truth more closely, and they found that the source of such emissions is a magnetar.
The recently discovered fast radio burst is another rare example of a repeating cosmic radio signal. In less than two months, FRB 20201124A gave astronomers the largest sample scientists have collected so far of a fast polarization radio burst.
The term polarization refers to the direction light waves take in three-dimensional space. Scientists can understand the environment through which light has passed by extrapolating the changes in its direction since it emanated from its source. For example, strong polarization indicates a highly magnetic environment, and so on.
Based on abundant information from FRB 20201124A, scientists have determined that the source of these recurring signals is a magnetar.
It seems that the source of the stream is not alone
Something strange was noticed, the way the polarization changed over time indicated that the strength of the magnetic field and the density of atoms around the magnetar were fluctuating.
“For me, it's like filming the vicinity of a fast radio source, and our film showed a complex dynamically evolving magnetized environment that we hadn't imagined before,” Zhang explained. Such an environment is not the first thing that comes to mind when thinking of a lone magnetar. There might be something else in the vicinity of this FRB, most likely a binary companion.”
The data suggest that the companion could be a hot, blue Be Star, which is often associated with neutron stars. Evidence for this was presented in a separate paper led by astronomer Fine Wang of Nanjing University in China. It is also worth noting that these stars have B-type spectra and scattering lines.
Another surprise was the source of the fast radio burst for the researchers
Magnetars are the nuclei of huge giant stars that collapsed in on themselves due to their own gravity, like all neutron stars. These stars were between 10 and 25 times the mass of the Sun, or even more if they were rich in metal.
Neutron stars are known to expend their fuel very quickly, resulting in a relatively short life that always ends up ejecting their material in an explosion called a supernova.
Due to the short lives of magnetars, it was believed that these young celestial bodies are located in regions of galaxies where stars are still forming, that is, stars are formed, live their short lives, and die, forming clouds of cosmic dust and materials that go into forming new stars, and so on. It's a beautiful cosmic life cycle, but herein lies the problem.
A new way of looking at things
The source of the fast radio burst (FRB 20201124A) is located in a galaxy very similar to the Milky Way. We know that it is not uncommon to find star-birth regions in our galaxy, which leads us to believe that no new generation of young stars is forming near the source of the outflow under study.
But (FRB 20201124A) is not the only case in which there is a fast radio flux source in a galaxy that is relatively free of star formation, and the number of such cases that we know about continues to grow, which suggests a lack of information available to us, a defect in the way of thinking or an important factor absent in the equation. When it comes to studying magnetars and FRB sources, it is clear that we need to reconsider what they are and where they might be located.
But knowing the characteristics of this source means that we have a clear starting point for re-taking this journey. Essentially, the work by Wang and colleagues suggests that Be-star-neutron star binaries are the best place to look for sources of fast radio bursts.
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