The team behind the first Chinese X-ray astronomy satellite, Insight-HXMT, has discovered the strongest magnetic field directly measured in the universe up till now.
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 translates to a surface magnetic field of more than 1.6 billion Tesla.
The findings were published last month in Astrophysical Journal Letters. They were obtained jointly 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.
Two years ago, the team detected a 90 keV cyclotron absorption line from a neutron star in the X-ray binary system GRO J1008-57, which corresponds to a surface magnetic field of 1 billion Tesla, which set a world record for direct measurement of the universe’s strongest magnetic field at the time.
This time, it beat its previous record by 60 percent.
A neutron star X-ray binary system has a neutron star and its companion star. The gas of the companion star falls towards the neutron star, which forms an accretion disk. In turn, the plasma in the accretion disk will fall along magnetic lines to the neutron star’s surface, releasing powerful X-ray radiation. Such emissions result in periodic X-ray pulse signals, resulting in the name “X-ray accretion pulsar.”
This phenomenon can be used to directly measure the strength of the magnetic field near the surface of a neutron star as the energy of the absorption structure is in line with the strength of the surface magnetic field.
Insight-HXMT made detailed and broadband observations of the outburst of Swift J0243.6+6124, the Milky Way’s first ultraluminous X-ray pulsar, and discovered its cyclotron absorption line. This particular line revealed energy up to 146 keV, which equals a surface magnetic field of more than 1.6 billion Tesla.
This is the first solid evidence that a neutron star’s magnetic field structure is more complex and nonsymmetric than a traditional symmetric component of a neutron star’s magnetic field.