Alien Communications? What Do These Radio Burst Mean?
Since one was first discovered in 2007, fast radio bursts have been a bit of perplexing puzzle for scientist to figure out. The first object within the Milky Way galaxy, SGR 1935+2154, is said to have spitting out two additional powerful radio signals consistent with those seen from extragalactic sources (Up until 28 April 2020 the fast radio bursts (FRBs) were only detected from millions of light-years away). In fact SGR 1935+2154 is the first definite source of the signals.
Then again on 24 May 2020 the Westerbork Synthesis Radio Telescope caught two millisecond-long radio bursts from the magnetar, 1.4 seconds apart. A much fainter FRB signal was also detected by the Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) in China on 3 May.
Scientist believe that one or more processes inside magnetars are producing these enigmatic bursts (not all the same strength). They also think SGR 1935+2154 could be a dream come true as an excellent way to understand these extremely powerful bursts of energy only in radio frequencies.
"Assuming that a single emission mechanism is responsible for all reported radio bursts from SGR 1935+2154, it has to be of such a type that the burst rate is close to independent of the amount of energy emitted across more than seven orders of magnitude," the researchers wrote in their paper.
"Alternatively, different parts of the emission cone might cross our line of sight if the beaming direction changes notably over time."
Magnetars are a type of neutron star, however we don't really know how they form (recent evidence suggests that colliding neutron stars could be one way). We know gravity pushes inward and the magnetic field pulls outward. This process distorts the magnetar's shape and produces magnetar quakes and magnetar flares, usually seen in high-energy X-rays and gamma radiation.
"It seems that the majority of X-ray/gamma-ray bursts are not associated with pulsed radio emission," the researchers wrote.
"The parameters and fluences that we measure for the X-ray bursts are consistent with typical values observed for SGR 1935+2154, fitting with the idea that radio bursts are instead associated with atypical, harder-X-ray bursts.
On 8 October 2020, it was recorded spitting out three more radio bursts, in a three-second period. That data is still under analysis, but it marks the beginning of a good collection of signals that could help us look for patterns, or clues as to the magnetar behaviour that spits them out (another recent paper suggests that magnetar quakes are responsible).
"So SGR 1935+2154 is not a flawless analogue of the extragalactic FRB population. Nonetheless, magnetars can plausibly explain the diverse phenomena observed from FRBs," the researchers wrote in their paper.
"Perhaps the distant, periodically active FRB sources are brighter and more active because they are substantially younger than SGR 1935+2154 and because their magnetospheres are perturbed by the ionised wind of a nearby companion. Similarly, perhaps non-repeating FRBs are older, non-interacting and thus less active. Detailed characterisation of FRB local environments is critical to investigating these possibilities."
The research has been published in Nature Astronomy.