Researchers investigate the origins of a swift radio burst

Extremely compact objects, like neutron stars and possibly black holes, can emit short, intense radio wave explosions known as “fast radio bursts.”. The energy contained in these brief fireworks, which last only a thousandth of a second, is sufficient to momentarily outshine entire galaxies.

Astronomers have identified thousands of fast radio bursts (FRBs) since the discovery of the first one in 2007. These FRBs can be found anywhere from 7 billion light-years away to within our own galaxy. It is hotly debated exactly how these cosmic radio flares are produced.

MIT astronomers have now used a new method to pinpoint the origin of at least one fast radio burst, and they may be able to do the same for other FRBs. The team’s new study, which was published in the journal Nature, concentrated on FRB 20221022A, a fast radio burst that was previously identified and detected from a galaxy located roughly 200 million light-years away.

By studying the radio signal’s “scintillation,” or how stars twinkle in the night sky, the team was able to pinpoint its exact location. Following an analysis of variations in the FRB’s brightness, the scientists concluded that the burst had to have come from close to its source rather than far away, as some models had suggested.

According to the team’s estimation, FRB 20221022A exploded from an area that is at most 10,000 kilometers away from a rotating neutron star. That is a shorter distance than Singapore and New York. The burst most likely originated from the magnetosphere of the neutron star, which is the highly magnetic area immediately surrounding the ultracompact star, given the close proximity.

The team’s results offer the first concrete proof that the magnetosphere, the extremely magnetic region immediately surrounding an extremely compact object, can be the source of a fast radio burst.

“The magnetic fields in these neutron star environments are really at the limits of what the universe can produce,” says lead author Kenzie Nimmo, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research. “Whether this bright radio emission could even escape from that extreme plasma has been hotly debated. “.

Kiyoshi Masui, an associate professor of physics at MIT, states that atoms cannot exist around these extremely magnetic neutron stars, also referred to as magnetars, because they would simply be destroyed by the magnetic fields.

The fascinating aspect of this situation is that we discover that the energy contained in those magnetic fields near the source is changing and rearranging itself to allow for its release as radio waves that are visible to us from halfway across the cosmos. “..”.

Adam Lanman, Daniele Michilli, Kaitlyn Shin, and Shion Andrew are co-authors of the study from MIT, with assistance from other universities.

Size of burst.

Because of the Canadian Hydrogen Intensity Mapping Experiment (CHIME), the number of fast radio burst detections has increased recently. Four sizable, stationary receivers in the shape of half pipes make up the radio telescope array. These receivers are tuned to pick up radio emissions in a range that is extremely sensitive to quick radio bursts.

CHIME has detected thousands of FRBs from across the universe since 2020. Though the precise physics causing the FRBs is unknown, scientists generally concur that the bursts originate from extremely compact objects.

Fast radio bursts are predicted by some models to originate in the turbulent magnetosphere immediately surrounding a compact object, while other models predict that the bursts should originate much farther out, as part of a shockwave that moves away from the central object.

In order to differentiate between the two situations and identify the locations of rapid radio bursts, the team took into account scintillation, which is the phenomenon that happens when light from a small, bright source, like a star, passes through a medium, like the gas in a galaxy.

From a distance, the starlight appears to be twinkling because of the way it bends as it passes through the gas. An object’s ability to twinkle increases with its size or distance. Because they undergo less bending, the light from larger or closer objects—like the planets in our own solar system—does not appear to twinkle.

The team reasoned that they could infer the relative size of the region from which the FRB originated if they could estimate the degree to which an FRB scintillates. The burst is more likely to have originated from a magnetically turbulent environment if the region is smaller and the burst is closer to its source. The idea that FRBs originate from distant shockwaves is supported by the fact that the burst would be farther in the larger region.

pattern of twinkles.

The researchers looked to FRB 20221022A, a fast radio burst detected by CHIME in 2022, to test their hypothesis. The signal has a duration of approximately two milliseconds and is a fairly typical FRB in terms of brightness.

But one property in particular stood out to the team’s McGill University collaborators. The angle of polarization traced a smooth S-shaped curve, indicating that the light from the burst was highly polarized. This pattern is taken to be proof that the FRB emission site is rotating, which has been noted in pulsars, which are rotating neutron stars with high magnetization.

It was a first to observe a similar polarization in fast radio bursts, indicating that the signal might have originated from a neutron star’s close-in vicinity. In a companion paper published in Nature, the McGill team presents their findings.

The MIT group reasoned that they should be able to use scintillation to demonstrate that FRB 20221022A came from a location near a neutron star.

The FRB was twinkling, or scintillating, according to Nimmo and her colleagues’ new study, which analyzed data from CHIME and showed sharp brightness variations. They verified the presence of gas bending and filtering radio waves somewhere between the telescope and FRB.

After figuring out where this gas might be found, the team was able to confirm that some of the scintillation seen was caused by gas inside the host galaxy of the FRB. As a result of this gas acting as a natural lens, the researchers were able to focus on the FRB site and ascertain that the burst came from a very small area, estimated to be around 10,000 kilometers wide.

The FRB is most likely within hundreds of thousands of kilometers from the source, according to Nimmo. “That is extremely near. For contrast, if the signal came from a shockwave, we would anticipate that it would be over tens of millions of kilometers away and that there would be no scintillation at all. “.

Masui explains that zooming in on a 10,000-kilometer area from a distance of 200 million light years is similar to measuring the width of a DNA helix on the moon’s surface, which is roughly 2 nanometers wide. “The range of scales involved is astounding. “.”.

FRB 20221022A could not have formed from the edge of a compact object, according to the team’s results and the McGill team’s findings. Rather, in extremely chaotic magnetic environments, the research demonstrates for the first time that rapid radio bursts can come from very close to a neutron star.

“ChIME detects several bursts a day, and these bursts are always happening,” Masui says. The way and location of these bursts can vary greatly, and this scintillation technique will be very helpful in separating the different physics that cause them. “.”.