An article published in the journal “Nature Astronomy” reports an explanation for the abrupt slowdown in the rotation of the magnetar cataloged as SGR 1935+2154 and its attribution to a sort of volcano that ejected a kind of wind into space. A team of researchers used X-ray data from ESA’s XMM-Newton space telescope and NASA’s NICER instrument to analyze changes in the magnetar. Their conclusion is that the activity of the pseudo-volcano altered the magnetar’s magnetic field, slowing down its rotation, what in jargon is called anti-glitch. That led to the beginning of radio wave emissions subsequently detected by the Chinese FAST radio telescope.
Magnetars are a type of neutron star with an extremely strong magnetic field. The processes inside neutron stars are not yet well understood and are being studied. Changes can occur inside a neutron star with the consequent increase in its rotation speed, what in jargon is called a glitch. Such a phenomenon was observed in Vela Pulsar, another type of neutron star. The opposite phenomenon is called anti-glitch in jargon.
These types of irregularities are rare and therefore interesting. The conditions inside a neutron star are extreme and their study helps to explore the frontiers of physics where the macroscopic of stars mixes with the submicroscopic of the ultra-compressed particles inside them. In the case of anti-glitches, this is a phenomenon that was observed only three times and had no explanation so far. This new study offers one.
On October 5, 2020, the magnetar SGR 1935+2154 abruptly slowed its rotational speed. This rotational slowdown was observed by the XMM-Newton space telescope and by the NICER (Neutron Star Interior Composition Explorer) instrument installed on the International Space Station precisely for the purpose of studying neutron stars.
According to the authors of this study, the anti-glitch of magnetar SGR 1935+2154 was caused by a pseudo-volcanic formation. It’s a formation that has analogies with volcanoes in the sense that it’s a fracture on the surface but instead of emitting magma, it emits powerful winds formed by particles. This can affect the magnetar’s angular momentum and magnetic fields resulting in a reduction in its rotational speed and more.
A few days after the anti-glitch, the magnetar SGR 1935+2154 generated radio emissions similar to fast radio bursts that were detected by the FAST radio telescope in China. The Vela Pulsar was also associated with this type of emission as well as a glitch, and this offers new information on the processes that can lead a neutron star to emit radio waves. Perhaps, both pulsars and magnetars can, under certain conditions, emit fast radio bursts.
These phenomena are temporary therefore continuous monitoring is necessary to detect them. The NICER instrument was designed precisely for the study of neutron stars and, together with other instruments that detect different bands of the electromagnetic spectrum, they are providing useful data to gradually understand what happens on and inside the various types of neutron stars.
