The rotating stars known as magnetars, neutron stars with a very strong magnetic field that spin on themselves hundreds of times per second, can be ‘cosmic engines’ of exceptional power: Italian researchers from the National Institute of Nuclear Physics, the National Institute of Astrophysics and American Stony Brook University, have in fact demonstrated for the first time that these objects can be the origin of gamma ray bursts, explosions of short duration and enormous luminosity among the most violent in the universe. The study, published in The Astrophysical Journal Letters, therefore sheds new light on one of the deepest and most investigated mysteries of astrophysics.
Gamma-ray bursts are thought to be produced in the process of the formation of a black hole, or in the merger of two neutron stars. In recent years, however, another hypothesis has been developed: the flashes could instead be generated by the formation of a magnetar, objects with a mass similar to that of the Sun concentrated in the volume of a large city.
According to the group led by Simone Dall’Osso, Infn researcher and Inaf associate, a newly formed magnetar initially captures part of the matter that is still falling following the gravitational collapse: this generates the initial and brightest part of the gamma-ray burst , releasing a huge amount of energy in a few tens of seconds. When the flow of matter decreases, the rotation of the star’s magnetic field begins to repel the matter itself, hurling it away, the energy released decreases and with it the luminosity, until the flash goes out.
“Our study explains the different phases of the emission of a gamma-ray burst and its gradual extinction,” comments Dall’Osso. “The physical processes involved are the same that operate in other systems, such as white dwarfs and ordinary neutron stars but, applied to a magnetar, these same processes lead to the release of enormous amounts of energy in very short times, with hallmarks that it is possible identify”.
Source: Ansa
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