Humanity's exploration of the Milky Way has made new discoveries!
Recently, Assistant Researcher Zhang Xiang of Shanghai Astronomical Observatory and Dr. Hurley-Walker of the International Radio Astronomy Research Center (ICRAR-Curtin) of Curtin University in Australia have discovered 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. The research was published online on January 27, 2022 in the journal Nature.
High-frequency radio skies shine with temporary objects such as supernova explosions, gamma-ray bursts, and black hole accretion disk flares, but low-frequency radio skies behave unusually quietly. And right now, that calm is being broken. The new generation of radio telescopes, represented by the SquareKilometreArray (SKA) and its pilot telescopes, is ushering in a new era of radio transient source research with deeper and broader observation capabilities than ever before.
It is reported that Zhang Xiang and Dr. Hurley-Walker and others have discovered a dense transient source with unusually slow periodic radiation by analyzing the sky survey observation data of the Murchison WidefieldArray (MWA) of the SKA low-frequency pilot telescope in Australia.
This tentative 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, each burst lasts about 30-60 seconds, including short time scale (>
△ Zhang Xiang and the research team colleagues
In the subsequent optical, infrared, and high-energy observations, the scientific research team did not find its counterpart. Dispersive measurements of its radio pulses show that this temporary source is located in the Milky Way, about 4200 light-years away from the solar system. Polarization measurements show that the linear polarization of this transient source is about 90%, exceeding all known pulsars in the same observation mode in the 150 MHz band (due to the smoothing effect caused by the observation method, the polarization of the pulsar line observed in this mode does not exceed 70%), 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. Once this secret temporary source was discovered, it caused widespread discussion on its nature in the international scientific community. The team believes it is more likely to be a Magnetar or a white dwarf with an ultra-strong 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 upper is the temporary source image, and the lower part is the schematic diagram of the MWA antenna (source: Australian International Radio Astronomy Research Center)
This discovery of the temporary source is due to the highly sensitive SKA low-frequency pilot radio telescope and the SKA computing cluster customized according to the characteristics of the SKA data. The second author of the paper, Zhang Xiang of the Shanghai Astronomical Observatory, undertook the 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 of the project, the amount of data generated by the data processing intermediate process is larger, the number of image files exceeds 10 million, the data processing process is complex, and the data processing software has extremely high requirements for the access input and output (IO) bandwidth, data IO bandwidth, high concurrent tasks and high parallelization processing of the computing cluster. Based on the above-mentioned characteristics and extremely high requirements of SKA polarization data processing, shanghai astronomical observatory, as a full member of MWA, 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.
△ Prototype of SKA Regional Center in China
Since its completion in November 2019, the SKA Regional Center Prototype in China has been one of the top ten astronomical scientific and technological advances in China for two consecutive years, and has been recognized as the "First International Prototype of SKA Regional Center" by SKAO (Square Kilometer Array Observatory Square Kilometre Array Institutionaly) International Organization. In this study, the Chinese SKA Regional Center prototype 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.
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Source: Oriental Network, netizen comments
Reporter: Fu Wenjing
Editors: Xia Xiaoxia, Shirley
Reviewer: Bian Yinghao