An international team of astronomers have discovered for the first time a colossal burst of energy generated by a magnetar in another galaxy, which was observed as a short gamma ray burst (GRB). The passage of radiation through the solar system was tracked by spacecraft located at different distances from the Earth. This is reported in articles published in the journals Nature and Nature Astronomy.
Gamma-ray burst GRB 200415A was detected on April 15, 2020 in the galaxy NGC 253, located at a distance of 11.4 million light years. Most GRBs last less than two seconds and are referred to as short GRBs. As a rule, they appear when two neutron stars revolving around each other collide. However, not all GRBs fit this scenario, and in some cases they are generated by magnetars.
There are 29 known magnetars in the Milky Way – neutron stars with extremely strong magnetic fields. Two emitted gamma-ray bursts, with the last one being emitted by a magnetar located 28,000 light-years away. It was recorded in 2004.
The new flare was detected by a high-energy neutron detector aboard the Mars Odyssey spacecraft orbiting Mars. After 6.6 minutes, the detector on the Wind satellite, located between the Earth and the Sun, was triggered, and after 4.5 seconds, the radiation hit the Earth. The pulse lasted 140 milliseconds.
It is believed that flares are caused by a sudden restructuring of the magnetic field of the magnetar, which is caused by starquakes. The findings provide some evidence of seismic activity on the neutron star. According to the theoretical model, a cloud of ejected electrons and positrons traveling at about 99 percent of the speed of light generated a shock wave and a powerful burst of gamma rays after the main burst.
According to scientists, high-energy flares from magnetars can occur five times more often than supernovae, and constitute a separate class of gamma-ray bursts.