(ORDO NEWS) — Scientists from the Institute of High Energy Physics of the Chinese Academy of Sciences and the University of Tübingen in Germany have discovered the strongest magnetic field in the universe in the X-ray double neutron star Swift J0243.6+6124. The results of the study are published in The Astrophysical Journal Letters.
Ultraluminous X-ray (ULX) sources are bright X-ray sources with an apparent luminosity greater than 10 to the 39th power of erg per second. Astronomers detect X-ray pulsations from such sources, indicating that these objects are accreting neutron stars with strong magnetic fields.
The strength of the latter can be reliably measured by cyclotron resonant scattering feature (CRSF), a phenomenon that occurs when X-ray photons are scattered by plasma electrons in the presence of a magnetic field.
The observations were made using China‘s Hard X-ray Modulation Telescope (HXMT) orbital X-ray observatory.
Scientists discovered the highest-energy CRSF known to date, at 146 kiloelectronvolts (keV), during the outburst of the first galactic source of pulsating ultra-bright X-rays, Swift J0243.6+6124, in 2017. This energy corresponds to a surface magnetic field of 1.6 billion Tesla.
An X-ray binary system consists of a neutron star and a companion star. Under the influence of the neutron star’s strong gravity, the companion’s gas falls onto the neutron star, forming an accretion disk.
The plasma in the accretion disk falls along magnetic lines onto the surface of the neutron star, releasing powerful X-rays.
Along with the rotation of the neutron star, such ejections lead to periodic X-ray pulses. Superluminous X-ray pulsars are a class of objects whose X-ray luminosity is much higher than that of canonical X-ray accreting pulsars.
In 2020, the Insight-HXMT team reported the detection of a 90 keV cyclotron absorption line from a neutron star in the GRO J1008-57 X-ray binary corresponding to a surface magnetic field of 1 billion Tesla.
Later, a neutron star was discovered with a maximum cyclotron scattering energy of about 100 keV. The new discovery broke this record.
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