Artist’s impression of a radio magnetar. Credit: CSIRO
On March 12th, 2020, an area telescope called Swift, identified a burst of radiation from half-way throughout the Milky Way. Within a week, the recently found X-ray source, called Swift J1818.0–1607, was discovered to be a magnetar: an unusual kind of gradually turning neutron star with among the most effective electromagnetic fields in the Universe.
Spinning when every 1.4 seconds, it’s the fastest spinning magnetar understood, and potentially among the youngest neutron stars in the Milky Way. It likewise produces radio pulses like those seen from pulsars — another kind of turning neutron star in our galaxy. At the time of this detection, just 4 other radio-pulse-emitting magnetars were understood, making Swift J1818.0–1607 an incredibly uncommon discovery.
In a just recently released research study led by a group of researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), it was discovered that the pulses from the magnetar ended up being substantially fainter when going from low to high radio frequencies: it has a ‘steep’ radio spectrum. Its radio emission is not just steeper than the 4 other radio magnetars, however likewise steeper than ~90% of all pulsars! Additionally, they discovered the magnetar had actually ended up being over 10 times brighter in just 2 weeks.
Comparatively, the other 4 radio magnetars have practically consistent brightness at various radio frequencies. These observations were used the Ultra Wideband-Low (UWL) receiver system set up on the Parkes radio telescope, likewise referred to as ‘The Dish’. Whereas most telescopes are restricted to observing radio waves throughout extremely narrow frequency strips, the Parkes UWL receiver can identify radio waves throughout an incredibly wide variety of frequencies all at the exact same time.
After additional analysis, the OzGrav group discovered fascinating resemblances to an extremely energetic radio pulsar called PSR J1119–6127. This pulsar went through a magnetar-like outburst back in 2016, where it too experienced a quick boost in brightness and established a high radio spectrum. If the outburst of this pulsar and Swift J1818.0–1607 share the exact same source of power, then gradually with time, the magnetar’s spectrum must start to appear like other observed radio magnetars.
The age of the young magnetar (in between 240-320 years), was determined from both its rotation duration and how rapidly it decreases with time; nevertheless, this is not likely to be precise. The spin-down rates of magnetars are extremely variable on year-long timescales, especially after outbursts, and can cause inaccurate age price quotes. This is likewise supported by the absence of any supernova residue—residues of luminescent outstanding surges—at the magnetars position.
Lead author of the research study Marcus Lower proposed a theory to discuss of the magnetar’s mystical residential or commercial properties: ‘Swift J1818.0–1607 may have started out life as a more ordinary radio pulsar that obtained the rotational properties of a magnetar over time. This can happen if the magnetic and rotational poles of a neutron star rapidly become aligned, or if supernova material fell back onto the neutron star and buried its magnetic field’.
The buried electromagnetic field would then gradually emerge back to the surface area over countless years. Continued observations of Swift J1818.0–1607, over numerous months to years, are required to check these theories.
Reference: “Spectropolarimetric Properties of Swift J1818.0–1607: A 1.4 s Radio Magnetar” by Marcus E. Lower, Ryan M. Shannon, Simon Johnston and Matthew Bailes, 18 June 2020, Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ab9898
