Discovery of three self-lensing binaries from Kepler

TL;DR

This paper reports the discovery of three self-lensing binary systems with white dwarf companions using Kepler data, providing precise mass measurements and insights into binary evolution.

Contribution

It presents the first systematic identification and modeling of self-lensing binaries with white dwarf companions, enabling accurate mass determinations and testing binary evolution models.

Findings

White dwarf masses are close to 0.6 Solar masses.

Orbital periods range from 419 to 728 days.

Eccentricities are all less than 0.2.

Abstract

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.