Lasting around a millisecond, fast radio bursts can come from all regions of the Universe, without knowing the phenomenon at the origin. If they generally appear only once, researchers have identified 25 rapid bursts which are repeated tirelessly. An increasingly intriguing observation!
They are among the most mysterious objects in the Universe. Fast radio bursts (FRB for Fast Radio Burst in English) release in a few milliseconds a energyenergy equivalent to that produced by the Sun in three days. And we don’t know where they come from. One hypothesis is that they would come from magnetars, neutron starsneutron stars with a particularly intense magnetic field. But the discovery of radio bursts in star-poor areas contradicts this idea. In total, there are more than 1,000 unveiled by the radiotélescoperadiotélescope Chime (Hydrogen Intensity Mapping Experiment), originally designed to calculate the vitessevitesse expansion of the Universe via cartographyhydrogenhydrogen.
Equipped to cover a range of frequenciesfrequencies ranging from 400 to 800 MHz, it performs a second mission in parallel: that of characterizing fast radio bursts and tracing them back to their source. However, among the various bursts, we find some that are recurrent, even periodic. It is on these signals that a publication available on arXiv and for which the Chime/FRB collaboration participated as first author. In 2021, it published a report identifying 18 new repetitive sources.
25 new repetitive radio sources identified
So far, only 19 repeating bursts have been detected, including only one proven periodic burst, FRB 180916, which occurs every 16.35 days. This time, the team used a new algorithm to search all signals spotted between 2019 and 2021 for those with the same dispersion measurement. This parameter corresponds to the deviation of receptionreception between the different signal frequencies.
“We can measure the position of the sky and the dispersion of the fast radio burst up to a certain precision which depends on the design of the telescope used.said Ziggy Pleunis in Universe Todayco-author of the study. The clustering algorithm takes into account all the fast radio bursts that the Chime telescope has detected and looks for groups of FRBs which have consistent positions in the sky and similar dispersion measurements. We then perform various checks to ensure that a group’s bursts are really coming from the same source. »
In total, they counted 25 new sources having repeated themselves at least once. Representing a fraction between 2.6% and 2.9% of repetitive bursts among all those detected. They also do not exclude the possibility that certain “unique” sources will return in the months or years to come. “ This great first is the result of Chime’s large field of vision, its high sensitivity and the daily study of a large area of sky”, enthuse the researchers in the study.
Differences in the properties of fast radio bursts
To distinguish repetitive bursts from others, the team tried to characterize each signal as much as possible. They noted that, on average, the dispersion measurement of repeater signals was lower than that of single signals. Moreover, as described in their conclusion, “repetitive bursts are observed to be longer in durationdurationand with a bandwidthbandwidth narrower than for bursts from non-repetitive sources”.
It remains to be seen whether these differences come directly from the source, or whether they are caused by propagation effects in distinct environments. To understand it, “Detailed population-based synthetic studies that take into account the many observational and instrumental biases will be needed to disentangle these effects”, concludes the study. Ultimately, the problem remains the same: the mysterious origin of fast radio bursts.
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