An eruption such as a volcanic eruption would have caused the magnetic field to drop

Artist’s impression of a magnetic explosion. Credit: NASA’s Goddard Space Flight Center

On Oct. 5, 2020, the rapidly rotating body of a dead star about 30,000 light-years from Earth changed speed. In a cosmic second, its spin slowed down. And a few days later, it suddenly started emitting radio waves.

Thanks to timely measurements from special orbiting telescopes, Rice University astronomer Matthew Baring and colleagues were able to test a new hypothesis about the possible cause of the decline. unusual, or “anti-glitch” of SGR 1935+2154, a strong magnetic field. a neutron star known as a magnetar.

In a study published this month by The Nature of Astronomy, Baring and co-authors used X-ray data from the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton) and NASA’s Neutron Star Interior Composition Explorer (NICER) to study the rotation of the magnetar. They suggested that the sudden decrease may have been caused by a volcanic eruption on the star that spewed a “wind” of massive particles into space. The research showed how such a wind could change the star’s gravity, conditions that could alter the radio emission measured by China’s Aperture Spherical Telescope ( FAST) of China.

Baring, a professor of physics and astronomy, said: “People have the idea that neutron stars can have the same number of volcanoes. “Our findings suggest that this may be the case and that in this case, the explosion would have occurred at or near the star’s magnetic field.”

SGR 1935+2154 and other magnetars are a type of neutron star, the compact remnant of a dead star that collapsed under its strong gravity. About 12 kilometers across and as dense as the nucleus of an atom, the magnets spin once every second and have the strongest gravitational pull in the universe.

Magnets emit high-energy radiation, including X-rays and sometimes radio waves and gamma rays. Astronomers can explain a lot about the unusual stars that come from that gas. By reading the intensity of X-rays, for example, physicists can calculate the rotation period of a magnetar, or the time it takes to make one complete rotation, as the Earth does in one day. The magnetic rotation period is usually very slow, taking tens of thousands of years to slow down to one rotation per second.

Glitches are sudden increases in rotational speed that are often caused by sudden changes in the star’s interior, Baring said.

He said: “In most cases of glitches, the pulsation period becomes shorter, which means that the star rotates faster than it used to.” “The textbook explanation is that over time, the outer, magnetic parts of the star slow down, but the inner, non-magnetic core does not. This leads to stress. at the boundary between these two areas, and glitch signals. a sudden transfer of rotational energy from the fast-spinning core to the slow-spinning core.”

Rapid deceleration of the magnetar is rare. Astronomers have reported only three “anti-glitches,” including the October 2020 event.

Although glitches can normally be explained by changes in the star, it is possible that anti-glitches cannot. The Baring theory is based on the idea that they are caused by changes in the surface of the star and the space around it. In the new paper, he and his co-authors developed a volcanic-driven wind model to explain the results measured from the October 2020 anti-glitch.

Baring says the model uses only ordinary physics, specifically energy transitions and conservation of energy, to account for the reduced circulation.

“A strong, strong wind from the star for a few hours can create conditions for the rotation period to drop,” he said. “Our calculations showed such a wind would also have the power to change the geometry of the gravitational field outside the neutron star.”

The eruption may have an eruption-like structure, because “general X-ray pulsation processes may require air to be generated from the atmosphere in the upper atmosphere.” ,” he said.

“What makes the October 2020 event unique is that there was a rapid burst of radio from the magnet only a few days after the anti-glitch, as well as the radio being switched on -and pulsed, ephemeral air shortly thereafter,” he said. “We’ve only seen a few transient magnetar radios, and this is the first time we’ve seen a nearly glitch-proof magnetar radio.”

Baring argued that this unexpected occurrence suggests that the gas glitch and the radio emissions were caused by the same event, and he hopes that the studies some of the volcanic eruptions will provide some answers.

“Spiritual analysis provides a way to understand why the radio is on,” he said. “It provides new insight that we didn’t have before.”

Additional information:
G. Younes et al, Magnetar spin-down glitch paves the way for FRB-like bursts and the radio constant, The Nature of Astronomy (2023). DOI: 10.1038/s41550-022-01865-y

Provided by Rice University

Excerpt: Volcanic-like eruption could have caused magnetar collapse (2023, January 27) Retrieved January 28, 2023 from volcano-like-rupture-magnetar-slowdown.html

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