Astronomers measure strongest magnetic field ever detected of a neutron star in our galaxy

Amazing stuff!

"... a powerful type of neutron star, with a surface magnetic field of over 1.6 billion Tesla. ...
The newly crowned record-holder is a binary star system known as Swift J0243.6+6124, in our home galaxy. ...
And this one is particularly bright, earning it the extra adjective of “ultraluminous.” ...
Using the Chinese X-ray astronomy satellite Insight-HXMT, the researchers used this method to calculate the magnetic field for Swift J0243.6+6124, and found it to be an incredible 1.6 billion Tesla. That’s the most powerful magnetic field ever detected in the universe by a huge margin – the previous record-holder was another pulsar with 1 billion Tesla, reported by the same team in 2020. For reference, the strongest magnetic field ever created here on Earth is a modest 1,200 Tesla. ..."

From the abstract:

"The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ∼2 × 1039 erg s−1, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60–70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ∼1.6 × 1013 G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario."

Astronomers measure strongest magnetic field ever detected

Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124 (open access)