Astronomers link “starkwakes” to mysterious radio signals from space

Research from the University of Tokyo links fast radio bursts (FRBs) to “stellar tremors” in neutron stars, providing new insights into earthquakes and nuclear physics.

Fast Radio Bursts or FRBs are an astronomical mystery, their exact cause and origin still unconfirmed. These intense bursts of radio energy are invisible to the human eye, but are brightly visible in radio telescopes. Previous studies have repeatedly noted broad similarities between the energy distribution of FRBs and earthquakes and solar flares.

However, new research at the University of Tokyo looked at the timing and energy of FRBs and found distinct differences between FRBs and solar flares, but also many striking similarities between FRBs and earthquakes. This supports the theory that FRBs are caused by “stellar tremors” on the surface of neutron stars. The discovery will help better understand aspects of earthquakes, the behavior of high-density matter, and nuclear physics.

Chinese Five Hundred Meter Aperture Spherical Radio Telescope (FAST). The FRB data were provided by the Five Hundred Meter Aperture Spherical Telescope (FAST) in China and the Arecibo Telescope in Puerto Rico, two of the world’s largest single-dish telescopes. Unfortunately, the Arecibo telescope was damaged and deactivated in 2020. Credit: Bojun Wang, Jinchen Jiang & Qisheng Cui

The puzzle of FRBs

The vastness of space holds many mysteries. While few dream of daring to go where no one has gone before, there is much we can learn from the comforts of Earth. Thanks to technological advances, we can explore the surface tuesdaysurprise Satrings, and pick up mysterious signals from deep space. Fast radio bursts are high-energy, bright bursts of energy visible in radio waves.

First discovered in 2007, these bursts can travel billions of light years, but typically last only a thousandth of a second. It is estimated that 10,000 FRBs could happen every day if we could observe the entire sky. Although most sources of bursts detected so far appear to emit a single event, there are about 50 sources of FRBs that emit repeated bursts.

Data on earthquakes are taken from Japan’s Kanto region (including Tokyo and Narita) and Izumo in the Tsukoku region (north of Hiroshima). Black dots indicate epicenters of earthquakes recorded between May 6, 2010 and December 31, 2012. Credit: ©2023 T. Totani & Y. Tsuzuki

Theories behind the cause of FRBs

The cause of FRBs is unknown, but some ideas have been put forward that may even be the origin. However, the current prevailing theory is that at least some FRBs are emitted by neutron stars. These stars form when a supergiant star collapses from a mass eight times that of our Sun (on average) to a center 20-40 kilometers across. Magnetos are neutron stars with very strong magnetic fields and are observed to emit FRBs.

“It was theorized that the surface of a magnet would experience a stellar earthquake, an energy release similar to earthquakes on Earth,” said Tomonori Totani, a professor in the Department of Astronomy at the Graduate School of Science. “Recent observational advances have led to the discovery of thousands more FRBs, so we had the opportunity to compare the large statistical data sets now available for FRBs with data from earthquakes and solar flares to explore possible similarities.”

The researchers analyzed the timing and energy distribution of FRB and earthquake events, and by plotting the regression probabilities as a function of time delay, found that the two are very similar. Credit: ©2023 T. Totani & Y. Tsuzuki

Statistical analysis and findings

So far, statistical analysis of FRBs has focused on the distribution of waiting times between two consecutive bursts. However, Totani and co-author Yuya Suzuki, a graduate student in the same department, point out that calculating only the waiting time distribution does not take into account correlations that exist across other outbreaks. By analyzing the timing and emission energy of nearly 7,000 bursts from three different repeater FRP sources, the team decided to calculate the correlation in two-dimensional space. They then used the same method to study time-energy correlations for earthquakes (using data from Japan) and solar flares (using records). Hinot International Mission for the Study of the Sun), and compared the results of three other cases.

Contrary to other studies, their analysis showed a striking similarity between FRBs and earthquake data, but Totani and Tsuzuki were surprised to find a distinct difference between FRBs and solar flares.

Totani explained: “The results show significant similarities between FRBs and earthquakes in the following ways: first, the probability of an aftershock of an event is 10-50%; Second, as a force of time, the regression incidence rate decreases with time; Third, although the FRB-earthquake activity (average rate) changes significantly, the regression rate remains constant; And fourth, there is no correlation between the energies of the mainshock and the aftershock.

This strongly suggests the presence of a solid crust on the surface of neutron stars, and sudden stellar wobbles in these crusts release large amounts of energy, which we see as FRBs. The team intends to continue analyzing new data on FRBs to verify that the similarities they found are universal.

“By studying stellar earthquakes in distant ultradense stars, environments that are completely different from Earth, we can gain new insights into earthquakes,” Totani said. “The interior of a Neutron star It is the densest place in the universe, comparable to the interior of the nucleus. Stellar earthquakes of neutron stars have opened up the possibility of obtaining new insights into the fundamental laws of ultra-dense matter and nuclear physics.

Note: “Fast radio bursts trigger aftershocks similar to earthquakes, but not solar flares” by Tomonori Totani and Yuya Suzuki, 11 October 2023, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad2532