May 29, 2013
Researchers Observe Bizarre ‘Anti-Glitch’ In Pulsar Star
John P. Millis, PhD for redOrbit.com — Your Universe Online
When a massive star — one several times larger than our Sun — consumes all of the fusible matter in its core, it begins to implode in a brilliant supernova. Driven by gravitational collapse, the core of the star will form either a neutron star or a black hole, depending upon its mass.While not quite as exotic or dense as a black hole, a neutron star is still an amazing object and provides a useful laboratory for exploring fundamental physics. So understanding these objects — their magnetic fields, their masses, their composition, their rotation, etc. — is of paramount importance for the fields of astronomy and astrophysics.
Even though neutron stars — often called pulsars because of their rapid rotation — have been studied for decades across the entire electromagnetic spectrum, there is still much that we are learning about their behavior. For instance, pulsars slow down over time as the rotational energy of the remnant is lost to the surrounding area. Occasionally, however, the star will “glitch,” causing its rotation to suddenly and dramatically accelerate.
Using data from NASA´s Swift X-ray satellite, researchers have found a new type of glitch. “I looked at the data and was shocked — the neutron star had suddenly slowed down,” says Rob Archibald, lead author and Masters student at McGill University. “These stars are not supposed to behave this way.”
Complicating the matter is that this particular object is actually a so-called magnetar — a pulsar that has an even more powerful magnetic field than normal pulsars. Known as 1E 2259+586, and located roughly 10,000 light-years away in the constellation of Cassiopeia, the glitch event was accompanied by a flare in the X-ray spectrum, an indication of a violent event at or near the remnant´s surface.
“We´ve seen huge X-ray explosions from magnetars before,” says Victoria Kaspi, professor of physics at McGill and leader of the Swift magnetar monitoring program. “But an anti-glitch was quite a surprise. This is telling us something brand new about the insides of these amazing objects.”
The cause of the anti-glitch is still unclear, but the research team believes that it is an indication of a previously undetected behavior below the surface of the pulsar. In fact, researchers hope that this discovery will provide renewed interest in studying neutron star interiors in general.