Insight-HXMTs discovery of the essential electron cyclotron absorption line near 146 keV for the very first Galactic ultraluminous X-ray pulsar Swift J 0243.6 +6124. Credit: Image by IHEP
Insight-HXMT Breaks Own Measurement Record for Strongest Magnetic Field in Universe
Neutron stars create the strongest magnetic fields in the universe. However, the only way we need to determine their surface electromagnetic field straight is to observe the cyclotron absorption lines in their X-ray energy spectra. Recently, the Insight-HXMT team discovered a cyclotron absorption line with an energy of 146 keV in the neutron star X-ray binary Swift J0243.6 +6124, which equates to a surface magnetic field of more than 1.6 billion Tesla.
After direct measurement of the strongest electromagnetic field in the universe at about 1 billion Tesla in 2020, the world records for the greatest energy cyclotron absorption line and direct measurement of the strongest magnetic field in the universe have been smashed by a large margin.
The findings, which were released on June 28, 2022, in Astrophysical Journal Letters (ApJL), were acquired collectively by the Key Laboratory for Particle Astrophysics at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences and the Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, University of Tübingen (IAAT). Dr. Lingda Kong, Professor Shu Zhang, and Professor Shuangnan Zhang from IHEP are the matching authors of the paper. Dr. Victor Doroshenko and Professor Andrea Santangelo from the University of Tübingen considerably added to the discovery.
Just recently, the Insight-HXMT group found a cyclotron absorption line with an energy of 146 keV in the neutron star X-ray binary Swift J0243.6 +6124, which translates to a surface area magnetic field of more than 1.6 billion Tesla.
Along with the rotation of the neutron star, such emissions result in periodic X-ray pulse signals, hence the name “X-ray accretion pulsar” for these objects.
Ultraluminous X-ray pulsars are a class of things whose X-ray luminosity far goes beyond that of canonical X-ray accreting pulsars. Insight-HXMT has benefits over other X-ray satellites in terms of broadband (1-250 keV) spectral protection, big reliable area at high energies, high time resolution, low dead-time, and no pile-up impacts for brilliant sources, therefore opening up a brand-new window for observing black holes, neutron stars with hard X-ray quick shifts, and energy spectrum studies.
In 2020, the Insight-HXMT team reported the detection of a 90 keV cyclotron absorption line from a neutron star in the X-ray binary system GRO J1008-57, corresponding to a surface magnetic field of 1 billion Tesla, which set a world record for direct measurement of the universes greatest magnetic field at the time.
A neutron star X-ray binary system includes a neutron star and its buddy star. Under the strong gravitational force of the neutron star, the gas of the buddy star falls towards the neutron star, forming an accretion disk. The plasma in the accretion disk will fall along magnetic lines to the neutron stars surface, where effective X-ray radiation is released. In addition to the rotation of the neutron star, such emissions lead to routine X-ray pulse signals, hence the name “X-ray accretion pulsar” for these objects.
Lots of observations have exposed that these types of items have absorption structures in their X-ray radiation spectra, specifically cyclotron absorption lines, which are thought to be triggered by resonant scattering and thus absorption of X-rays by electrons moving along the strong electromagnetic fields. The energy of the absorption structure represents the strength of the surface electromagnetic field of a neutron star; therefore, this phenomenon can be utilized to straight determine the strength of the electromagnetic field near the surface of the neutron star.
Insight-HXMTs discovery of the essential electron cyclotron absorption line near 146 keV for the very first Galactic ultraluminous X-ray pulsar Swift J 0243.6 +6124. Credit: Image by IHEP
Ultraluminous X-ray pulsars are a class of items whose X-ray luminosity far surpasses that of canonical X-ray accreting pulsars. They have actually formerly been found in a number of galaxies far from the Milky Way. Astronomers have actually speculated that their pulsars have high magnetic field strengths although direct measurement evidence is still lacking.
Insight-HXMT made in-depth and high speed observations of the outburst of Swift J0243.6 +6124, the Milky Ways first ultraluminous X-ray pulsar, and unambiguously discovered its cyclotron absorption line. This line exposed energy up to 146 keV (with detection significance of about 10 times the standard discrepancy), which represents a surface area magnetic field of more than 1.6 billion Tesla. This is not just the strongest electromagnetic field straight determined in deep space to date however likewise the very first detection of an electron cyclotron absorption line in an ultraluminous X-ray source, thus providing direct measurement of the neutron stars surface area magnetic field.
It is thought that the surface magnetic fields of neutron stars have complex structures, ranging from dipole fields really far from the neutron star to multipole fields only affecting the location near the neutron star. Most earlier indirect quotes of the magnetic fields of neutron stars have actually penetrated only the dipole fields.
This time, the direct magnetic field measurement by Insight-HXMT based upon the cyclotron absorption line has to do with an order of magnitude higher than that estimated utilizing indirect ways. This serves as the first concrete proof that a neutron stars magnetic field structure is more complicated than that of a traditional symmetric dipole field, and it likewise supplies the very first measurement of the nonsymmetric part of a neutron stars electromagnetic field.
Referral: “Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6 +6124” by Ling-Da Kong, Shu Zhang, Shuang-Nan Zhang, Long Ji, Victor Doroshenko, Andrea Santangelo, Yu-Peng Chen, Fang-Jun Lu, Ming-Yu Ge, Peng-Ju Wang, Lian Tao, Jin-Lu Qu, Ti-Pei Li, Cong-Zhan Liu, Jin-Yuan Liao, Zhi Chang, Jing-Qiang Peng and Qing-Cang Shui, 28 June 2022, Astrophysical Journal Letters.DOI: 10.3847/ 2041-8213/ ac7711.
The Hard X-ray Modulation Telescope (HXMT), also referred to as Insight, is a Chinese X-ray observatory released on June 15, 2017 aboard a Long March 4B rocket from the Jiuquan Satellite Launch Center. The objective provides high resolution images across a broad spectrum of X-ray energies.
Insight-HXMT is the very first Chinese X-ray astronomy satellite. It consists of scientific payloads consisting of a high-energy telescope, medium-energy telescope, low-energy telescope, and a space environment monitor. Insight-HXMT has advantages over other X-ray satellites in terms of broadband (1-250 keV) spectral coverage, big reliable area at high energies, high time resolution, low dead-time, and no pile-up results for intense sources, hence opening a brand-new window for observing great voids, neutron stars with difficult X-ray quick shifts, and energy spectrum studies.
In 2020, the Insight-HXMT group reported the detection of a 90 keV cyclotron absorption line from a neutron star in the X-ray binary system GRO J1008-57, representing a surface area electromagnetic field of 1 billion Tesla, which set a world record for direct measurement of deep spaces greatest electromagnetic field at the time. Later, a new record for a cyclotron absorption line– with its greatest energy around 100 keV– was detected by Insight-HXMT from another neutron star in 1A 0535 +262. Insight-HXMT has actually demonstrated its remarkable capability to explore the energy spectrum by breaking its own records for cyclotron absorption line discoveries.
Insight-HXMT was proposed by Professor Tipei Li and Professor Mei wu in 1993 at IHEP and was effectively introduced on June 15, 2017. IHEP was responsible for satellite payloads, ground segments, and scientific research for this objective. The calibration of the detectors on board Insight-HXMT was supported by the National Institute of Metrology, Ferrara University in Italy, and the Max Planck Institute for Extraterrestrial Physics.