  We report the discovery of three edge-on binaries with white dwarf companions
that gravitationally magnify (instead of eclipsing) the light of their stellar
primaries, as revealed by a systematic search for pulses with long periods in
the Kepler photometry. We jointly model the self-lensing light curves and
radial-velocity orbits to derive the white dwarf masses, all of which are close
to 0.6 Solar masses. The orbital periods are long, ranging from 419 to 728
days, and the eccentricities are low, all less than 0.2. These characteristics
are reminiscent of the orbits found for many blue stragglers in open clusters
and the field, for which stable mass transfer due to Roche-lobe overflow from
an evolving primary (now a white dwarf) has been proposed as the formation
mechanism. Because the actual masses for our three white dwarf companions have
been accurately determined, these self-lensing systems would provide excellent
tests for models of interacting binaries.

Solar and Stellar Astrophysics