For the first time, Chinese and foreign scientists have discovered a new object with a super magnetic field in the Milky Way

The high-frequency radio sky shines with temporary objects such as supernova explosions, gamma-ray bursts, and black hole accretion disk flares, but the low-frequency radio sky behaves unusually "quiet". Today, this "calm" is being broken. The new generation of radio telescopes, represented by the Square Kilometer Array Radio Telescope (SKA) and its pilot telescopes, is ushering in a new era of radio transient source research with deeper and broader observation capabilities than in the past.

Recently, Zhang Xiang, an assistant researcher at the Shanghai Astronomical Observatory, and Dr. Hurley-Walker of the International Radio Astronomy Research Center of Curtin University in Australia, analyzed the sky survey observation data of the SKA pilot telescope and found a radio transient source with unusually slow periodic radiation. The research team believes that the radio transient source may be an ultra-long-period magnetar or a white dwarf with a super-strong magnetic field. On January 27, the results of the research were published online in Nature.

A new window opens for the search for low-frequency temporary sources

The temporary appearance originated in early 2018, and its burst period is about 18 minutes, which is 9 times longer than the longest known pulsar burst period, and each burst lasts about 30-60 seconds, including short time scale (>

The study found that this temporary source is located in the Milky Way, about 4200 light-years away from the solar system. Polarization measurements show that the transient source has a linear polarization of about 90%, exceeding all known pulsars in the same observation mode in the 150 MHz band, indicating that the transient source has an ultra-strong magnetic field. The long-period and high polarization of the transient source cannot be explained by the theoretical models and observational characteristics of known pulsars, thus ruling out the possibility that it is an ordinary pulsar. The team believes that it is more likely to be a magnetar or a white dwarf with a super magnetic field.

This discovery opens a new window for the search for low-frequency transient sources: due to the complex radio radiation structure and strong interstellar flicker in the silver channel surface area, in most previous low-frequency radio survey projects, the search for the temporary source is often limited to the area far from the silver channel surface, and there is no systematic search for the temporary source with a cycle of a few minutes to a few hours.

This discovery is the first detection of long-period temporary sources in the galactic surface region, and if more transient sources with similar characteristics can continue to be detected and their physical properties revealed, it means that there is a class of long-period stars with super magnetic fields in the Milky Way, which will contribute to a comprehensive understanding of the evolution and death of stars. The team is conducting a systematic search to discover more stars of this type and build a large sample for statistical studies to fill in the gaps in magnetometric research.

The SKA Regional Center prototype in China participates in data processing

This discovery is due to the highly sensitive SKA Low Frequency Pilot Radio Telescope Murchison Wide field Array (MWA) and the SKA Computing Cluster tailored to the characteristics of SKA data.

Xiang Zhang, the second author of the paper, undertook polarization calibration and polarization data analysis in this work and produced three key images in the paper. Due to the huge amount of raw data for the project, the amount of data generated by the data processing process is staggering (more than 10 million image files), and the data processing process is complex. As a full member of MWA, Shanghai Astronomical Observatory has carried out a series of scientific research on SKA's key scientific goals with the support of the Ministry of Science and Technology of the People's Republic of China, the Chinese Academy of Sciences, the SKA China Office and the Shanghai Municipal Science and Technology Commission, using the self-developed prototype of the China SKA Regional Center. In this research work, the SKA Regional Center prototype in China undertook the storage of part of the MWA data of the project, participated in the processing of wideband polarization data, completed the analysis of partially polarized images, and completed other data processing tasks together with the computing equipment of SKA Regional Center in Australia.

Since its completion in November 2019, the prototype of China's SKA Regional Center independently developed by Shanghai Observatory has won China's top ten astronomical scientific and technological progress for two consecutive years, and has been recognized as "the first SKA Regional Center Prototype in the World" by the Square Kilometer Array Observatory (SKAO) International Organization, and will continue to provide computing resources and technical support for the large-scale sky survey project of the SKA Pilot Telescope in the future, helping SKA scientists around the world to produce more original results.

Related Links:

The Square Kilometre Array Radio Telescope (SKA) is the world's largest integrated aperture radio telescope planned to be built by international astronomers. The SKA consists of a 2,500 15 m diameter dish antenna array (intermediate frequency), 250 dense aperture arrays, and 1.3 million logarithmic periodic antenna arrays (low frequencies), with a total reception area of one square kilometer and a reception frequency covering 50 MHz-20 GHz. The SKA's site is located in a radio quiet area in eight countries in Australia, South Africa and Southern Africa, and the entire array extends over 3,000 kilometers.