On March 12, 2020, the Swift space telescope discovered an outbreak in the Milky Way galaxy. Within a week, the recently discovered X-ray source Swift J1818.0–1607, a magnetar, a rare type of slowly rotating neutron star with one of the most powerful magnetic fields in the universe, was identified. A group of scientists from the Center for Advanced Research on Gravitational Waves (OzGrav) recently discovered new magnetar properties, a study published in The Astrophysical Journal Letters.
Spinning once every 1.4 seconds, this is the fastest known spinning magnet and possibly one of the youngest neutron stars in the Milky Way. In addition, the Swift star J1818.0–1607 emits radio signals similar to those observed in pulsars – another type of rotating neutron stars. At the time of discovery, only four other radio-impulse magnetars were known, which makes Swift J1818.0–1607 an extremely rare discovery.
Recently, researchers found that the pulses from the magnetar become weaker when moving from low to high radio frequencies: it has a steep radio spectrum. Its radio emission is not only cooler than four other radio magnets, but also about 90% of all pulsars. In addition, scientists found that the magnetar in just two weeks became brighter by more than 10 times.
In comparison, four other radio magnets have an almost constant brightness at radio frequencies.
The age of a young magnetar, from 240 to 320 years, was measured both by the period of its rotation and by how quickly it slows down over time. However, these data are unlikely to be accurate. The rate of deceleration of the rotation of magnetars varies greatly throughout the year, especially after outbreaks, and can lead to incorrect estimates of age. This is also confirmed by the absence of any supernova remnant in the position of the magnetars.
The lead author of the study, Marcus Lawer, proposed a theory explaining the mysterious properties of a magnetar. Swift J1818.0–1607 could begin its life as a regular radio pulsar, which eventually gained the rotational properties of a magnetar. This can happen if the magnetic pole and the rotation poles of the neutron star are quickly aligned, or if the material of the supernova falls back onto the neutron star and bury its magnetic field.
Then a latent magnetic field will slowly float back to the surface for thousands of years. To verify these theories, constant observations of Swift J1818.0–1607 are required for months or years.