A team of U.S.-Canadian astronomers has conducted radial velocity observations of four binary white dwarf candidates. They report that two of them, designated WD 0311−649 and WD 1606+422, are apparently double-lined spectroscopic binary systems. The finding is detailed in a paper published February 14 on arXiv.org.
Source:
https://phys.org/news/2020-02-double-lined-spectroscopic-binary-white-dwarfs.html