The unexpected change in brightness was observed in only one of these stars, which is feeding from an accretion disk around its companion. The more it "nourishes", the more its light increases. The phenomenon could be followed using NASA's Transiting Exoplanet Survey Satellite (TESS) space telescope. The observations were carried out by an international team, led by an expert from the University of Durham, UK. The group saw abrupt drops and surprising brightness increases.
Scientists believe there is something interfering with the white dwarf's feeding — probably its magnetic field. When her glow is “on”, the star picks up material from the companion's disk. When its luminosity dims, it's because the field rotates so fast that a centrifugal barrier prevents the disc's fuel from falling onto the white dwarf. In other words, the star's rotating magnetic field acts as a “magnetic gate” that regulates the entry of helium and hydrogen into the accretion disk. This ends up altering the luminosity that is seen by astronomers until the system “turns on” again and the light returns to normal.
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