We have detected a strange new signal from the time and space rift.
A recurring fast radio burst source detected last year was recorded spitting 1,863 bursts over 82 hours, amid a total of 91 hours of observation.
This hyperactive behavior allowed scientists to they characterize not only the galaxy that hosts the source and its distance from us, but also what the source is.
The object, called FRB 20201124A, was detected by the Five Hundred Meter Spherical Radio Telescope (FAST) in China and described in a new paper led by astronomer Heng Xu of Peking University in China.
So far, most evidence points to a magnetar – a neutron star with extremely strong magnetic fields – as the source of FRB emissions like this.
If FRB 20201124A is indeed from one of these wild cosmic beasts, it looks like an unusual specimen.
“These observations brought us back to the drawing board,” says astrophysicist Bing Zhang of the University of Nevada, Las Vegas.
“It is clear that FRBs are more mysterious than we have imagined. More multi-wavelength observing campaigns are needed to further reveal the nature of these objects.”
Fast radio bursts have puzzled astronomers since they were first discovered 15 years ago, in archival data dating back to 2001: A spike of incredibly powerful radio emission lasting just a blink of time.
Since then, many more have been detected: millisecond-long bursts of radio waves, emitting at the time as much power as 500 million Suns.
Most that have been recorded have erupted only once, making them difficult to study (let alone understand). A tiny handful have been found to repeat themselves, which has helped scientists at least pinpoint the galaxies that host them.
Then, in 2020, a breakthrough. For the first time, a fast radio burst has been detected in our Galaxy – leading astrophysicists to trace the phenomenon to magnetic activity.
This latest outstanding FRB example is another example of a rare repeater. In less than two months of observation, FRB 20201124A has given astronomers the largest sample of polarized fast radio burst data of any FRB source.
Polarization refers to the orientation of light waves in three-dimensional space. By looking at how much this orientation has changed since the light left its source, scientists can understand the environment through which it has passed. Strong polarization indicates a strong magnetic environment, for example.
Based on the wealth of data delivered by FRB 20201124A, astronomers were able to conclude that the source is a magnetar.
But there was something strange. The way the polarization changed over time suggests that the magnetic field strength and particle density around the magnetar fluctuated.
“I liken it to shooting a movie about the environment of an FRB source, and the movie revealed to us a complex, dynamically evolving, magnetized environment that had never been imagined before,” Zhang explains.
“Such an environment is not immediately expected for an isolated magnet. Something else may be close to the FRB engine, possibly a binary companion.”
That companion, the data suggest, could be a hot, blue Be-type star, which is often found in neutron star companions. Evidence for this was presented in a separate paper, led by astronomer Fayin Wang of Nanjing University in China.
But there was also something else strange.
As a type of neutron star, magnetars are the damaged cores of massive stars that, having run out of fuel to burn and provide external pressure, collapse under their own gravity.
Such stars burn through their fuel quickly and are short-lived, shedding their outer material in a supernova as the core collapses.
Because their lives are so short, these young magnets are thought to be in regions where star formation is still occurring. Stars live out their short lives and die, creating more clouds of material to give birth to more stars. It is a beautiful cosmic life cycle.
But FRB 20201124A was found in a galaxy very similar to the Milky Way. There isn’t much star formation here at home, so there shouldn’t be a stellar baby boom near our unusual new FRB friend.
However, FRB 20201124A is not the only FRB source found in a relatively star-forming galaxy.
The growing number suggests that there is some vital piece of information we may be missing, some hole in our understanding of FRB magnetars, how they form, and the locations they inhabit.
But characterizing the source means we have a new place to look for answers. The work by Wang and his colleagues suggests that binary neutron-Be stars may be one of the best places to look for fast radio burst-like signals.
Both papers have been published in Nature and Nature communications.