New views of a very strange and mysterious star located about 15,000 light-years away from Earth have revealed a strange pattern of stellar activity that astronomers say they have never seen before.
That star is called Swift J1818.0–1607 and was only discovered last year. Swift J1818.0–1607 is the so-called magnetar – a rare species of neutron star, which forms when large stars do not move to a supernova, instead falling into a supernova. very dense rights.
Unlike most neutron stars, however, magnetars are notorious for emitting an extremely powerful magnetic field. Only about 30 of these strange objects have ever been found in the Milk Trail, but even among the strange ones, Swift J1818.0–1607 is rare.
That’s because only a handful of known magnetars have ever been seen emitting radio waves of a pulsars-like type – another type of neutron star, much more common than magnetars, but nonetheless remarkable for the way in which they carry radiation pulses from their magnet poles.
However, in the midst of this special cover of ‘loud radio’ magnetars, none have ever been seen pushing in the same way as Swift J1818.0–1607, forcing some in the astronomy community to say that it may represent a kind of “missing connection” between magnetars and pulsars.
Now, a series of new astronaut-led ideas from the ARC Center of Excellence for Gravitational Wave Detection (OzGrav) in Australia does nothing to suggest that Swift J1818.0–1607’s reputation for strangely accomplished.
In eight observations with a five-month Parkes CSIRO radio telescope in 2020, the researchers looked at the radio beats of the magnetar changing significantly in character – similar to pulsar pulses in May, then changing to an inter- different of clear / weak blinking in June. , before taking a mysterious combination of pulsar- and magnetar-like radio beats in July.
Artist’s impression of Swift J1818.0–1607. (OzGrav / Carl Knox)
In the researchers’ new study, they describe this identity crisis of sorts in a scientific sense, says Swift J1818.0–1607 “[exhibited] the great evolution of the image of time over this period “.
But don’t let that language fool you into thinking this wasn’t a wonderful thing.
“This strange behavior has never been seen in any other radio-high magnetism,” the study’s lead author, Marcus Lower of Swinburne University and CSIRO explains.
“Apparently it was just a short-term surprise because with our next observation it was permanently settled in this new magnetar-like state.”
While the mixed messages contained in Swift J1818.0–1607 cannot be fully explained, the researchers suggest that the variables may represent a kind of stellar evolution that we have not yet developed. fully understand.
In part, this is because although this magnetar may be one of a kind (for now), the fact that magnetars in general, not to mention high-end magnetars, still represent a range very young study.
“This raises a number of questions,” explained Lower The Sydney Morning Herald.
“This magnetar from a pulsar may have become more consistent over time… or we may be missing other magnetars in the Milky Way because they are so far away from us that the low frequency radio waves we see too scattered for us to find. “
In other words, this strange behavior may be more normal than we know, it is just limited in what we currently understand about magnetars. However, we are finding out more all the time.
Swift J1818.0–1607’s new observations show that the magnetic axis of the magnet is not aligned with its rotational axis, but instead enters the southern hemisphere. If so, that’s the first for a magnetar – whose magnetic fields are mostly the same as their spinning axis.
But it could also explain some of the changes in the profile of observed radio emissions, which may reflect radio beats being emitted at different heights around the surface of the neutron star.
At least one data point, however – a view called MJD 59062 on August 1 last year – does not correspond to that version of events. But the team also has an hypothesis for MJD 59062.
“Our best geometric model for this date suggests that the radio conduction moved to a completely different magnetic pole in the northern hemisphere of the magnetar,” Lower says. .
The researchers say that an ongoing review of Swift J1818.0–1607 will help us find out what’s going on here.
“We are looking closely at our data to try and catch one of these flippers as it happens, because if we can do that we could map the magnetic field between the magnetic poles. , “said Lower The Sydney Morning Herald.
“Knowledge of the true geometry of magnetars is also very important in neutron star theory and being able to predict how they will grow over time.”
The results are reported in Monthly notices from the Royal Astronomical Society.