The volcano-like rupture could have caused magnetic deceleration

An artist’s impression of a magnetar burst. Credit: NASA’s Goddard Space Flight Center

On October 5th, 2020, the rapidly rotating corpse of a long-dead star about 30,000 light-years from Earth changed speeds. In a cosmic moment, its rotation slowed down. A few days later, it suddenly started emitting radio waves.

Thanks to timely measurements from specialized orbiting telescopes, Rice University astrophysicist Matthew Baring and his colleagues were able to test a new theory about a possible cause of the rare slowdown, or “flaw resistance,” of SGR 1935+2154, a highly magnetic type of neutron star known as a .

in a study Posted this month in natural astronomyBaring and co-authors used X-ray data from the European Space Agency’s X-ray Multi-Mirror Mission (ESA).XMM-Newton) and NASA’s Neutron Star Interior Structure Explorer (Nice) to analyze the rotation of the magnetar. They showed that the sudden slowdown could have been caused by a volcano-like rupture on the star’s surface that sent a “wind” of massive particles out into space. The research determined how such winds might alter a star’s magnetic fields, seeding conditions that likely triggered radio emissions later measured by the Chinese Five Hundred Meter Aperture Spherical Telescope (Quickly).

“People speculated about that “It could have the equivalent of volcanoes on its surface,” said Baring, a professor of physics and astronomy. “Our results suggest that this could be the case, and on this occasion, the rupture was most likely at or near the star’s magnetic pole.”

SGR 1935+2154 and other magnetars are a type of neutron star, which are the compacted remains of a dead star that collapsed under the influence of intense gravity. About ten miles wide and as dense as a nucleus of an atom, magnetars rotate once every few seconds and feature the most intense magnetic fields in the universe.

Magnets emit intense radiation, including X-rays, and sometimes and gamma rays. Astronomers can decipher a lot about the unusual stars from those emissions. By counting the X-ray pulsations, for example, physicists can calculate the period of rotation of a magnetar, or the amount of time it takes for one complete rotation, as Earth does in a day. The rotation periods of magnetars usually change slowly, taking tens of thousands of years to slow down by one cycle per second.

Glitches are sudden increases in Most of them, Baring said, result from sudden transformations deep within the star.

“In most glitches, the period of the pulsation becomes shorter, which means the star is spinning a little faster than it was,” he said. “The textbook explanation is that over time, the star’s magnetized outer layers slow down, but the non-magnetic inner core does not. This leads to a buildup of pressure at the boundary between these two regions, and signals an abrupt transfer of rotational energy from the faster core to the slowly rotating crust.”

A sudden slowing of the rotation of magnetars is very rare. Astronomers have recorded only three “glitches”, including the October 2020 event.

While glitches can routinely be explained by changes within the star, it likely cannot. Baring’s theory is based on the assumption that they are caused by changes in the star’s surface and in the space around it. In the new paper, he and his co-authors built a volcano-driven wind model to explain the measured results from October 2020 of imbalance control.

Baring said the model uses only standard physics, specifically changes in and energy conservation, to account for hysteresis in rotation.

“A strong and massive particle wind emanating from the star for a few hours could create the conditions for a lower rotation period,” he said. “Our calculations showed that such winds would also have the potential to alter geometry outside the neutron star.

The rupture could be a volcano-like formation, he said, because “the general characteristics of the X-ray pulsation likely require winds to be released from a specific area on the surface.”

“What makes the October 2020 event unique is that there was a fast radio burst from the magnetron just a few days after the fault, as well as a triggering of an ephemeral pulsed radio emission shortly thereafter,” he said. “We’ve only seen a few transiting, pulsating magnetars, and this is the first time we’ve seen a radio switch of a near-synchronous magnetar with an anti-fault.”

Baring argued that this coincidental timing suggests an antidote to a glitch Because of the same event, he hopes that additional studies of the volcano model will provide more answers.

“The wind interpretation provides a path to understanding why the radio emission is triggered,” he said. “It provides a new insight that we didn’t have before.”

more information:
Yunus et al., Magnetar rotation defect paves way for FRB-like bursts and pulsating radio loop, natural astronomy (2023). DOI: 10.1038/s41550-022-01865-y

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the quote: Volcano-like rupture could have caused magnetic slowdown (2023, January 27) Retrieved January 28, 2023 from

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