  Over 40% of Sun-like stars are bound in binary or multistar systems. Stellar
remnants in edge-on binary systems can gravitationally magnify their
companions, as predicted 40 years ago. By using data from the Kepler
spacecraft, we report the detection of such a "self-lensing" system, in which a
5-hour pulse of 0.1% amplitude occurs every orbital period. The white dwarf
stellar remnant and its Sun-like companion orbit one another every 88.18 days,
a long period for a white dwarf-eclipsing binary. By modeling the pulse as
gravitational magnification (microlensing) along with Kepler's laws and stellar
models, we constrain the mass of the white dwarf to be ~63% of the mass of our
Sun. Further study of this system, and any others discovered like it, will help
to constrain the physics of white dwarfs and binary star evolution.
