While ESA's Integral was observing the sky, it suddenly spotted a burst of gamma-rays coming from...
While ESA's Integral was observing the sky, it suddenly spotted a burst of gamma-rays coming from the nearby galaxy M82. Only a few hours later, ESA's XMM-Newton searched for an afterglow from the explosion but found none.
For only a tenth of a second, a short burst of energetic gamma-rays appeared from the direction of the bright galaxy M82. The satellite data were received in the Integral Science Data Centre in Geneva, from where a gamma-ray burst alert was sent out to astronomers worldwide, only 13 seconds after its detection.
The IBAS software gave an automatic localisation coinciding with the nearby galaxy M82. Now it was up to astronomers to figure out what had happened; was this one of the more common gamma-ray bursts or a rare occasion of a giant flare from a magnetar? .
"We immediately realised that this was a special alert. Gamma-ray bursts come from far-away and anywhere in the sky, but this burst came from a bright nearby galaxy," explains Sandro Mereghetti of the National Institute for Astrophysics in Milan, Italy, and lead author of a paper on this discovery.
"Some young neutron stars have extra strong magnetic fields, more than 10 000 times that of typical neutron stars. These are called magnetars. They emit energy away in flares, and occasionally these flares are gigantic," clarifies Ashley Chrimes, Research Fellow at ESA. .
In the past 50 years of gamma-ray observations, only three giant flares have been seen from magnetars in our galaxy.
"The flare detected by Integral is the first confirmation of a magnetar outside of the Milky Way. We suspect that some of the other 'short gamma-ray bursts' Integral and other satellites have revealed are also giant flares from magnetars," continues Sandro.
In these regions massive stars are born, live short turbulent lives and leave behind a neutron star.
The discovery of a magnetar in this region confirms that magnetars are likely young neutron stars.
Notes to editorsThe paper A magnetar giant flare in the nearby starburst galaxy M82 by Mereghetti et al.