NASA’S Swift Reveals New Phenomenon in a Neutron Star

Observations of X-ray pulses from 1E 2259+586 from July 2011 through mid-April 2012 indicated the magnetar’s rotation was gradually slowing from once every seven seconds, or about eight revolutions per minute. On April 28, 2012, data showed the spin rate had decreased abruptly, by 2.2 millionths of a second, and the magnetar was spinning down at a faster rate.

“Astronomers have witnessed hundreds of events, called glitches, associated with sudden increases in the spin of neutron stars, but this sudden spin-down caught us off guard,” said Victoria Kaspi, a professor of physics at McGill University in Montreal. She leads a team that uses Swift to monitor magnetars routinely.

Interesting. I had heard about stars “settling” and that’s fairly easy to imagine: if a star contracts slightly, its moment of inertia gets smaller. Because there is no external torque involved, angular momentum is conserved, and so it must speed up as a result. But a decrease in the spin?

I like that they call this an anti-glitch.