Has the cosmic mystery been solved? Extreme stars may hold the key to mysterious radio bursts

Has the cosmic mystery been solved?  Extreme stars may hold the key to mysterious radio bursts

Magnetar magnetic field radio wave emissions

Researchers have discovered a universal scaling law in neutron stars, including magnetars, that may explain mysterious fast radio bursts (FRBs). By studying the infrastructure of their radio emissions, they found commonalities in their rotation periods, enhancing our understanding of these celestial phenomena.

A global relationship for pulsars, magnetars, and possible fast radio bursts.

An international research team led by Michael Kramer and Kuo Liu from the Max Planck Institute for Radio Astronomy in Bonn, Germany, studied the rare object. Classify of extremely dense stars, called magnetars, to reveal a fundamental law that seems to apply universally to a group of objects known as neutron stars. This law gives insight into how these sources produce radio emission and may provide a link to mysterious flashes of radio light, fast radio bursts, originating from the distant universe.

The results are published in the journal Nature astronomy.

Magnetic artistic impression

Figure 1: Artist’s impression of a magnetar. A neutron star emits radio light powered by energy stored in an ultra-strong magnetic field, causing explosions that are among the most powerful events ever observed in the universe. Credit: © Michael Kramer/MPIfR

Understanding neutron stars

Neutron stars are the collapsed cores of massive stars, concentrating up to twice the mass of the Sun into a sphere less than 25 kilometers (15 miles) in diameter. As a result, the matter there is the densest matter in the observable universe, with electrons and protons compressed to form neutrons, hence the name. More than 3,000 neutron stars can be observed as radio pulsars, when they emit a radio beam that can be seen as a pulsating signal from Earth, when the star rotates. Pulsar It shines its light toward our telescopes.

Magnetars and their unique properties

The magnetic field of pulsars is already a thousand billion times stronger than the Earth’s magnetic field, but there is a small group of neutron stars that have magnetic fields 1,000 times stronger! These are so-called magnetars.

Of about 30 known magnetars, six have also been found to emit radio, at least occasionally. Extragalactic magnetars are thought to be the origin of fast radio bursts (FRBs). In order to study this connection, researchers from the Max Planck Institute for Radio Astronomy (MPIfR), with the help of colleagues at the University of Manchester, examined the individual pulsations of magnetars in detail and discovered the substructure in them. It turns out that a similar pulsating structure is also seen in pulsars, millisecond pulsars, and other pulsars. Neutron star Sources known as Rotating Radio Transients.

Discovery of the law of universal measurement

To their surprise, the researchers found that the time scales of magnetars and other types of neutron stars all follow the same universal relationship, scaling exactly with the rotation period. The fact that a neutron star with a rotation period of less than a few milliseconds and a neutron star with a rotation period of about 100 seconds behave like magnetars suggests that the fundamental origin of the subpulse structure must be the same for all neutron stars with a high radio frequency. . It reveals information about plasma The process responsible for the radio emission itself, and provides an opportunity to explain similar structures that appear in fast radio bursts as a result of a corresponding rotation period.

Insights from the research team

“When we set out to compare the emission of magnetars with the emission of fast radio bursts, we expected similarities,” recalls Michael Kramer, first author of the paper and director of MPIfR. “What we didn’t expect was that all the loud radio neutron stars share this global scale.”

“We expect magnetars to be powered by magnetic field energy, while other stars are powered by their own rotational energy,” Ku Liu continues. “Some of them are old, some of them are very young, and yet they all seem to follow this law.”

Effelsberg Radio Telescope

Effelsberg 100 meter radio telescope. Credit: © Raymond Speaking (CC BY-SA 4.0)

Gregory Desvigny describes the experiment: “We observed magnetars using the 100-meter radio telescope in Eifelsberg and also compared our results with archival data, since magnetars do not emit radio emissions all the time.”

“Since radio emission from a magnetar is not always present, one has to be flexible and react quickly, which is possible with telescopes like the one in Eifelsberg,” emphasizes Ramesh Karuppusamy.

Connecting FRBs and magnetars

For Ben Stubbers, co-author of the study, the most exciting aspect of the result is the possible connection to fast radio bursts: “If at least some of the fast radio bursts originate from magnetars, the time scale of the infrastructure in the explosion may tell us the period of rotation.” From the primary magnetic source. If we find this periodicity in the data, it will be a milestone in interpreting this type of fast radio bursts as radio sources.

“With this information, the search begins!” Michael Kramer concludes.

additional information

Magnetars are among the most active neutron stars, due to their extremely high magnetic fields. Of the above-mentioned 30 magnetars discovered to date, only six are known to exhibit radio emission. Recently, research interest in their properties has increased dramatically due to their possible association with fast radio bursts (FRBs). Fast radio bursts (FRBs) are millisecond-long bursts of radio emission generated by extragalactic sources. Although the origin of these radio bursts is not yet understood, magnetars are expected to be one possible source of fast radio bursts.

A substructure with concentrated short-duration emission was detected in the radio signal of pulsars shortly after they were first discovered. Typically, the substructure has a quasi-periodic characteristic and width, both of which have been found to expand with the period of the pulsar’s rotation. This relationship has been established in fundamental pulsars for decades, and has expanded to include the number of millisecond pulsars in recent years. More recently, the same type of short-duration “micropulses” has also been seen in some fast radio bursts, suggesting a similar underlying emission process in both scenarios.

The research used observations of all six loud magnetars made by the 100-meter Eifelsberg telescope in the CX band (4-8 GHz) and a few other 100-meter-class radio telescopes around the world.

Reference: “Quasi-periodic subpulse structure as a unifying feature of radio-emitting neutron stars” by Michael Kramer, Kuo Liu, Gregory Desevenes, Ramesh Karuppusamy, and Ben W. Stubbers, 23 November 2023, Nature astronomy.
doi: 10.1038/s41550-023-02125-3

Authors of the paper are Michael Kramer, Qu Liu, Gregory Desvines, Ramesh Karuppusamy, and Ben W. Stubbers. The first four authors all belong to the Max Planck Institute for Radio Astronomy.

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