Astronomers have directly confirmed four previously hidden white dwarf stars in nearby binary systems, according to ScienceDaily. Each system is located within 65 light-years of Earth.
The discoveries were made by researchers at the University of Warwick and the University of Colorado Boulder, and the results were published in the Monthly Notices of the Royal Astronomical Society. In each case, a white dwarf was found orbiting alongside a red dwarf star that had made the pair appear to be a single star in visible light.
The systems first drew attention because the visible stars showed a noticeable radial wobble, which can indicate the pull of an unseen companion. Researchers then used ultraviolet spectrograph data from the Hubble Space Telescope and developed calibration methods to separate white dwarf signals from ultraviolet flares produced by red dwarfs.
One of the systems, called G 203-47, was especially surprising. It is only 25 light-years away and is now recognized as the ninth closest white dwarf to the Sun. The team also found that its red dwarf rotates more slowly than expected for a closely orbiting pair, suggesting that not all of these binaries evolved in the same way.
The findings helped update estimates of white dwarf systems within 20 parsecs, or 65 light-years, of the Sun. Researchers said the number found matches earlier population models, but they also noted that many nearby red dwarfs have not yet been checked for hidden white dwarf companions.
