Gravitational redshift determinations for white dwarfs in common proper-motion binaries

Gravitational redshifts determined using the 5 m Hale telescope are given for 23 white dwarfs belonging to common proper-motion binary systems and additional velocities are presented for 14 pairs found not to comprise physical binaries or that have unmeasurable velocities. The mass distribution for the common proper-motion pairs using the gravitational redshifts and the mass-radius relation peaks strongly near 0.55 solar mass, and the main details of the shape agree with earlier determinations using other methods although a problem remains with contamination with optical pairs. The redshifts and radii of a subset of these objects with known distances are consistent with the mass-radius relation for white dwarfs. 30 refs.