A Spectroscopic Survey of Southern Hemisphere White Dwarfs-III: BINARIES CONTAINING A WHITE DWARF

Both components of five proper motion binaries containing a white dwarf have been studied spectroscopically. A coarse differential analysis has been carried out on the bright, non-degenerate components and gravitational redshifts have been measured for the white dwarfs. From the present ages of the binaries as determined from theoretical isochrones, it is concluded that all of the white dwarfs in the present study have formed from stars that underwent mass-loss. From the present masses of the white dwarfs, up to about one solar mass could have been lost during the formation of a white dwarf. The star HR 2274 which has a DB star as a companion seems to be slightly metal enriched and deficient in s-process elements, while HR 6094 and HR 5864 have strong H and K Ca II emission. It is suggested that both effects could be due to mass-loss from the companion stars that are now white dwarfs.