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An international group of astronomers has obtained the first clues about extremely rare giant eruptions lasting 3.5 milliseconds that emerged from a magnetar located 13 million light years away. The team includes astronomers from Norway, Spain and the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital.
Magnetars are a type of isolated neutron stars that possess the most intense magnetic fields. They experience violent eruptions or intense bursts in the form of transient X-ray pulses which are several orders higher than that of the Sun. Even inactive magnetars can be thousands of times more luminous than the Sun.
So far, only 30 magnetars located within the Milky Way have been discovered.
The eruption that occurred on April 15, 2020 â described in the latest study published in Nature âwas from a magnetar named GRB2001415. Scientists involved in the research say that the single event released energy equivalent to what the Sun would radiate in one lakh years.
âThe observations revealed multiple pulses, first of which lasted for about tens of microseconds â which is much faster than other extreme astrophysical transients,â said Alberto J Castro-Tirado, lead author and scientist at the Instituto de AstrofĂsica de AndalucĂa (IAA â CSIC), Spain.
Found in the Sculptor group of galaxies (NGC 253), the detection of eruptions from GRB2001415 is significant as it is the farthest ever magnetar eruption detected by far.
âThe detection of eruptions from a magnetar located outside our galaxy is rare,â said Shashi Bhushan Pandey, senior scientist at ARIES, and one of the co-authors of the study.
Like earthquakes on Earth, magnetars suffer starquakes produced on their crust due to high instability prevailing in their magnetospheres. This instability triggers Alfven waves that are also common in the Sun. The interactions between multiple Alfven waves ultimately release massive energies, appearing as giant flares lasting for a few milliseconds.
The detection would have been nearly impossible without Atmosphere-Space Interactions Monitor (ASIM) on board the International Space Station and its wide effective area, coupled with complex data analysis performed by the scientists.
âASIM was the only mission that detected the main burst phase in the entire energy range of photons without saturation,â said second author Nikolai Ăstgaard, from the University of Bergen, Norway.
The study could further pave the way in linking how magnetic stresses are produced around neutron stars, said the researchers.
