Astronomers have observed for the first time that a white star that is accreting suddenly loses and increases its brightness. White dwarfs are stars that have exhausted their basic fuel: hydrogen. Usually, researchers observe that white dwarfs lose their brightness within days or months. Astronomers are studying the white dwarf binary star system TW Pictoris, in which the white dwarf loses its brightness within 30 minutes, which surprised astronomers. Astronomers say it is accreting, or drawing energy from the energy of its orbiting companion. To observe this unique phenomenon, astronomers use NASA’s Transiting Exoplanet Survey Satellite (TESS), which helps to find planets.

The brightness of a white does not depend on its own hydrogen source because it has exhausted it. Its brightness depends on the amount of surrounding matter on which it depends. Researchers said that the sudden opening and closing of the white dwarf may be due to some interference with the food supply.

The research was led by Durham University in the United Kingdom. The research results will be published in the journal Natural Astronomy on October 18, 2021.

TW Pictoris consists of a white star and a smaller companion star. White dwarfs obtain energy from accretion disks, which are fueled by hydrogen and helium from companion stars. The more energy it absorbs, the brighter it becomes.

The researchers noticed the sudden and fall of the white dwarf’s brightness, which they had never seen before. They think this may be caused by the reconfiguration of the magnetic field on the surface of the white dwarf.

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In the brightest phase, white dwarfs feed on accretion disks. But suddenly, the magnetic field to spin so fast that it created a centrifugal barrier. This prevents fuel from the accretion disk from reaching the white dwarf.

“Magnetic gating” the fuel from the disk to the white dwarf. As a small amount of fuel through the “gate”, the brightness of the white will increase slightly and semi-regularly.

Then, the system “turns on” again, the white to eat normally from the disk. Brightness reached its peak again.

Lead author Dr. Simone Scaringi said: “This is indeed a previously unknown phenomenon, because we can compare with similar behavior in much smaller neutron stars, which may help us better understand how other accreting objects absorb. An important step in the process of accumulation. Feeding on the materials surrounding them, and the important role of the magnetic field in this process.”

This extraordinary observation may lead to further research on white dwarfs and neutron stars.


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