Magnetars are a special subset of the isolated neutron star family, with X-ray and radio emission mainly powered by the decay of their immense magnetic fields.
On October 5, 2020, SGR 1935+2154 — a magnetar some 30,000 light-years away in the constellation of Vulpecula — changed speeds. And a few days later, it abruptly started emitting radio waves.
In the new study, Rice University’s Professor Matthew Baring and his colleagues used X-ray data from ESA’s X-ray Multi-Mirror Mission (XMM-Newton) and NASA’s Neutron Star Interior Composition Explorer (NICER) to analyze the magnetar’s rotation.
They showed the sudden slowdown could have been caused by a volcano-like rupture on the surface of the star that spewed a wind of massive particles into space.
They identified how such a wind could alter the star’s magnetic fields, seeding conditions that would be likely to switch on the radio emissions that were subsequently measured by China’s Five-hundred-meter Aperture Spherical Telescope (FAST).
“People have speculated that neutron stars could have the equivalent of volcanoes on their surface,” Professor Baring said.
“Our findings suggest that could be the case and that on this occasion, the rupture was most likely at or near the star’s magnetic pole.”
Magnetars emit intense radiation, including X-rays and occasional radio waves and gamma rays. Astronomers can decipher much about the unusual stars from those emissions.
By counting pulses of X-rays, for example, they can calculate a magnetar’s rotational period, or the amount of time it takes to make one complete rotation, as the Earth does in one day.
The rotational periods of magnetars typically change slowly, taking tens of thousands of years to slow by a single rotation per second.
“Glitches are abrupt increases in rotational speed that are most often caused by sudden shifts deep within the star,” Professor Baring said.
“In most glitches, the pulsation period gets shorter, meaning…
Read the full article here