Astronomers have revealed the strange behavior of the radio-loud magnetar Swift J1818.0-1607, which is a neutron star with an extremely strong magnetic field. Such objects are known as the strongest magnets in the universe. This is reported in an article published in the Monthly Notices of the Royal Astronomical Society.
Magnetar was discovered in March 2020 by a powerful X-ray flash. After that, the object sent unusual radio pulses that were different from those of other radio loud magnetars. While radio pulses are typically consistent across a wide range of observed frequencies, J1818’s pulses are much brighter at low frequencies than at high frequencies, making it look like a pulsar. In the new work, scientists observed the magnetar with the CSIRO Parkes radio telescope from May to October 2020.
In May, the magnetar was still emitting unusual pulsar-like pulses, but by June it began to flicker, oscillating between pulsar-like and magnetar radio pulses. This behavior is unique and has never been seen before in any such object.
Also, J1818’s magnetic axis is not aligned with the rotation axis, like many other magnetars. The radio-emitting magnetic pole was located in the southern hemisphere of the star, just below the equator. According to the data, this geometry is stable for this object. However, on August 1, 2020, it turned out that the radio beam briefly switched to a completely different magnetic pole located in the northern hemisphere of the magnetar. J1818 has a horseshoe-shaped magnetic configuration, unlike most ordinary neutron stars.