Swift J1818.0-1617 is located approximately 22,000 light-years away in the constellation of Sagittarius.
An artist’s impression of the magnetar Swift J1818.0-1617. Image credit: NSF / AUI / NRAO / S. Dagnello.
Discovered in 2020, Swift J1818.0-1617 is believed to be the fastest-spinning, rotating with a spin period of 1.36 seconds, and the youngest magnetar discovered thus far.
Situated on the other side of the Milky Way’s bulge and 22,000 light years away, the star’s position is relatively close to Earth.
Close enough, in fact, to utilize the parallax method to accurately determine its 3D location within our Galaxy.
The lifespan of a magnetar is unknown at this time, but astronomers estimate that Swift J1818.0-1617 is only a few hundred years old.
“A magnetar’s bright X-ray emissions necessitate a mechanism of extremely high energy outflow; only the rapid decay of its intense magnetic field can explain the power behind these spectral signatures,” said Dr. Hao Ding, an astronomer at the National Astronomical Observatory of Japan, and colleagues.
“But that, too, is an extreme process. For ordinary stars on the main sequence, bright blue stars live very short lives because they burn through their fuel far faster than their yellow siblings.”
“The physics is different for magnetars, but they, too, likely have shorter lifespans than their pulsar relatives.”
“Magnetars are very young, because they cannot continue giving off energy at this rate for very long,” they added.
“In addition, magnetars can also exhibit emissions at the low end of the electromagnetic spectrum — in radio wavelengths.”
“For these, synchrotron radiation from the magnetar’s fast spin is likely the energy source.”
“In synchrotron radiation, plasma surrounding the neutron star itself is so tightly wrapped against the star’s surface that it rotates at very nearly the speed of light, generating emissions in radio wavelengths.”
The astronomers used NSF’s Very Long Baseline Array (VLBA) over a period of three years to collect data on the position and velocity of Swift J1818.0-1617.
“The VLBA provided us with superb angular resolution for measuring this teeny-tiny parallax. The spatial resolution is unparalleled,” Dr. Ding said.
Swift J1818.0-1617’s parallax is among the smallest for neutron stars, and its so-called transverse velocity as the smallest — a new lower limit — among magnetars.
“Velocity in astronomy is most easily described as having two components, or directions,” the researchers explained.
“Its radial velocity describes how fast it is moving along the line of sight, which in this case means along the radius of the Galaxy.”
“For a magnetar such as Swift J1818.0-1617, located on the other side of the central bulge, there is too much other material in the way to precisely determine radial velocity.”
“Transverse velocity, sometimes called peculiar velocity, describes motion perpendicular to the plane of the Galaxy, and is more readily discernible.”
As astronomers try to understand the formation processes that are common — and those that are different — between regular neutron stars, pulsars, and magnetars, they hope to use precise measurements of transverse velocity to help parse out conditions that cause a star to evolve down one of these three paths.
“This study adds weight to the theory that magnetars are unlikely to form under the same conditions as young pulsars, thus suggesting that magnetars come into being under more exotic formation processes,” Dr. Ding said.
“We need to know how fast the magnetar was moving when it was just born. The formation mechanism of magnetars is still a mystery we would like to understand.”
Source : Breaking Science News