Hydrogen-Atmosphere White Dwarfs Are Less Likely To Be Found with Wide-Binary Companions

The fraction of white dwarfs found in wide binaries is estimated by cross referencing a catalogue of wide binaries with catalogues photometrically determined white-dwarf candidates and spectroscopically confirmed white dwarf stars. The wide-binary fraction of white dwarfs with hydrogen-dominated atmospheres is about 5%, but the fraction of white dwarfs with helium or carbon-dominated atmospheres is significantly larger. Using spectroscopic classifications, the binary fraction of DA white dwarfs is determined to be $0.063\pm 0.002$ and for non-DA white dwarfs is larger at $0.080\pm 0.004$.