Strange white dwarf switches 'on' and 'off' in front of astronomers - Space.com

This observation represents the first time astronomers saw a white dwarf change its luminosity, or inherent brightness, so quickly, and may have implications for how we understand the process of accretion (or building up material) at many types of celestial objects.

The luminosity changes took place because the white dwarf is pulling off material from a nearby companion star, in a process known as accretion.

As the white dwarf "feeds" off its companion, it grows brighter. .

The white dwarf lost luminosity in only 30 minutes, much faster than other white dwarfs that have faded over several days or months.

Why is still unknown, as the flow of material on to the white dwarf's accretion disc should be constant, but astronomers suspect it might be due to fluctuations in the dwarf's magnetic field.

"The brightness of an accreting white dwarf is affected by the amount of surrounding material it feeds on, so the researchers say something is interfering with its food supply," the University of Durham, which led the research, said in a statement.

The researchers theorize that when the star is "on," the white dwarf is feeding off the accretion disc as expected.

But when the star turns "off," it's possible that the magnetic field is spinning quite rapidly, too fast to allow the material from the companion star to settle on the white dwarf.

This process, which creates a centrifugal barrier blocking the material from falling on the white dwarf, is called "magnetic gating," the researchers said.

The new observations of the white dwarf, Scaringi added, "could be an important step in helping us to better understand the process of how other accreting objects feed on the material that surrounds them, and the important role of magnetic fields in this process.".