A magnetar is a neutron star with a magnetic subject hundreds of situations additional potent than those of common neutron stars. Their fields are so solid that they can produce impressive, limited-duration events this sort of as tender gamma repeaters and rapidly radio bursts. Although we have learned fairly a bit about magnetars in recent decades, we continue to do not fully grasp how neutron stars can form this kind of rigorous magnetic fields. But that could shortly transform many thanks to a new review.

Site of the 2017 kilonova through gravitational waves. Credit rating: LIGO Scientific Collaboration & Virgo Collaboration et al

In Might of this yr, astronomers observed the most highly effective kilonova ever noticed. Kilonovae manifest when two neutron stars (or a neutron star and black gap) collide, making a supernova-like explosion. They were very first discovered in 2010 by their intensive burst of gamma rays. In 2017 a kilonova was noticed by both of those gamma rays and gravitational waves, confirming their origin as a neutron star merger.

But the kilonova seen this calendar year was unusually dazzling. It was 10 occasions brighter than astronomers assumed probable, which raised issues about the structure of neutron stars. If your examine my write-up from a couple of days ago, you’ll don’t forget the interior structure of a neutron star can establish whether or not a merger generates a black gap or one thing else.

How a magnetar could account for the brilliant kilonova. Credit: NASA, ESA, and D. Player (STScI)

In this circumstance, the team looked at the light from the kilonova in radio and near-infrared. These wavelengths seize light-weight not from the merger alone, but from the heated product bordering it. They uncovered that if the two neutron stars collapsed into a black gap, there wouldn’t be more than enough electrical power to create the quantity of gentle developed at these wavelengths. But if the merger developed a magnetar, its strong magnetic subject could increase the electricity of the encompassing fuel. This would account for the extraordinary brightness of the kilonova.

This analyze doesn’t validate that a magnetar was created in this merger. There are other mechanisms that may possibly account for the brightness as perfectly, but the formation of a magnetar appears the most most likely result in. Magnetars are relatively exceptional amongst neutron stars, and that would explain why most kilonovas aren’t just about as dazzling as this recent a single. It also implies we may possibly have to wait a when before the following dazzling kilonova presents us more facts.

Reference: Fong, W., et al. “The Wide-band Counterpart of the Quick GRB 200522A at z = .5536: A Luminous Kilonova or a Collimated Outflow with a Reverse Shock?arXiv preprint arXiv:2008.08593 (2020).