Recently, after directly measuring the cosmic magnetic field of about 1 billion Teslas in 2020, the “Wise Eye” satellite team has measured more than 1.6 billion Tesla’s cosmic magnetic field, which has greatly refreshed the world record for direct measurement of the strongest magnetic field in the universe. The results were published online in the international journal Journal of Astrophysics Newsletter. Dr. Kong Lingda, Researcher Zhang Shu and Researcher Zhang Shuangnan of the Institute of High Energy of the Chinese Academy of Sciences are the corresponding authors of the paper.
Art map of clairvoyant satellite observation accretion pulsars. (Courtesy of Institute of High Energy Physics, Chinese Academy of Sciences)
This time, when observing the explosion of Swift J0243.6+6124, the first ultra-bright X-ray pulsar in the Milky Way, researchers found a cyclotron absorption line with an energy of up to 146 kiloelectronvolts, corresponding to the surface magnetic field of a neutron star of more than 1.6 billion Tesla.
“The reason why we want to study the magnetic field on the surface of the neutron star is to understand the formation process of neutron stars. At the same time, in the strong magnetic field of neutron stars, we can also further study physical phenomena such as quantum electrodynamics. Kong Lingda told China Science Daily.
Kong Lingda introduced that in the past, astronomers have found ultra-bright X-ray pulsars in many galaxies outside the Milky Way, and they speculated that their pulsars have a high magnetic field intensity, but there is no direct measurement evidence.
Swift J0243.6+6124 is a neutron star X-ray binary star system, which consists of neutron stars and their accompanying stars, and the gas accompanying the stars falls to the neutron star under the strong gravitational action of the neutron star, forming a gas disk rotating at high speed around the neutron star, that is, an accretion disk. The material on the accretion disk will fall along the magnetic field lines of the neutron star to the surface of the neutron star, emitting a strong X-ray radiation, which forms a periodic X-ray pulse signal as the neutron star rotates, so such objects are also called “X-ray accretion pulsars”.
In the past, astronomers have observed that X-ray accretion pulsars will have a “recessed” structure on the X-ray radiation energy spectrum, which is caused by the resonance scattering absorption of X-ray photons that swirl in the magnetic field, so it is called “cyclotron absorption line”. The gyratory absorption line is the only method scientists use to directly measure the strength of the magnetic field near the surface of a neutron star. The magnetic field strength corresponding to the energy at the cyclotron absorption line is the magnetic field strength on the surface of the neutron star.
In 2020, the “Eye” satellite detected a 90-kiloelectron-volt cyclotron absorption line in a neutron star numbered GRO J1008-57, corresponding to the 1 billion Tesla neutron star surface magnetic field, which was the world record for direct measurement of the cosmic magnetic field at that time. Subsequently, the “Eye” team also detected a gyratory absorption line of about 100 kiloelectron volts on the energy spectrum of another neutron star ( 1A 0535 +262 ) .
The observations of the “Eye” satellite are not only the highest record for direct measurement of the magnetic field of celestial bodies in the universe so far, but also the first time that the surface magnetic field of neutron stars has been directly measured in an ultra-bright X-ray accretion pulsar.
Kong Lingda said that the “Huiyan” satellite has set the highest record for the energy measurement of the cyclotron absorption line for three consecutive times, showing that it has a unique ability to detect the high-energy X-ray energy spectrum of celestial bodies.
First proposed in 1993 by Li Tibei, Wu Mei and others of the Institute of High Energy of the Chinese Academy of Sciences, the “Huiyan” satellite is China’s first X-ray astronomical satellite, carrying three scientific payloads and space environment monitors: high-energy X-ray telescopes, medium-energy X-ray telescopes and low-energy X-ray telescopes. Compared with foreign X-ray satellites, the “Wise Eye” satellite has outstanding advantages such as wide coverage of energy segments, the largest effective area in the high-energy X-ray energy segment, high time resolution, small detection death time, and no photon accumulation effect of observation strong sources, which opens a new window for observing black holes, neutron star hard X-ray rapid light change and energy spectrum research.
The “Wise Eye” satellite was launched in June 2017, and in June this year, the “Wise Eye” satellite, which was originally designed to have a lifespan of four years, has been in orbit for five years.
Kong Lingda introduced that the Enhanced X-ray Time-Varying and Polarization Space Observatory (eXTP), a major international cooperation space science project initiated and led by Chinese scientists, will further conduct in-depth research on the magnetic field related problems of neutron stars. (Source: China Science Daily Ni Sijie)
Related paper information:https://doi.org/10.3847/2041-8213/ac7711