  A spectroscopic analysis of the DAB white dwarf PG 1115+166 is presented. The
observed hydrogen and helium line profiles are shown to be incompatible with
model spectra calculated under the assumption of homogeneous or stratified
chemical compositions. In contrast, an excellent fit to the optical spectrum of
PG 1115+166 can be achieved if the object is interpreted as an unresolved
double degenerate composed of a hydrogen-line DA star and a helium-line DB
star. The atmospheric parameters obtained from the best fit are Teff=22,090 K
and log g=8.12 for the DA star, Teff=16,210 K and log g=8.19 for the DB star.
This binary interpretation is consistent with the results recently reported by
Burleigh et al. that PG 1115+166 also exhibits radial velocity variations. The
implications of this discovery with respect to the DAB spectral class are
discussed.
