Searching for GEMS: Discovery of the Nearby Post-common-envelope Binary System TIC-460388167*

Abstract Short-period white dwarf + main-sequence binaries are post-common-envelope binaries (PCEBs) that have survived a common envelope phase. Such systems, if detached and eclipsing, enable precise measurements of the constituent stars, providing a unique opportunity to probe the effects of the common envelope phase on the system. We report the discovery of one such nearby (57 pc) system, TIC-460388167, using a combination of multiband photometric light curves and spectroscopic radial velocities. In addition to eclipses, the system exhibits a continuously variable light curve that we model as a combination of ellipsoidal variations and starspots. We determine a period P = 0.63596258 ± 0.00000012 day and inclination i = 89 . ° 0 ± 0 . ° 4. The best-fitting model specifies a white dwarf with T 1 = 7607 ± 127 K and radius R 1 = 0.0131 ± 0.0003 R ⊙ , which is eclipsed by a T 2 = 3151 ± 59 K, R 2 = 0.327 ± 0.006 R ⊙ M dwarf. The white dwarf mass is 0.61 ± 0.04 M ⊙ . We present the first velocity-resolved profile for a PCEB secondary and show that the rotation of the M dwarf is synchronous with the orbital period, as expected. We compare the constituent stars to other PCEB systems and find that TIC-460388167A is one of the coolest known white dwarfs in such systems. TIC-460388167 is among the longest-period eclipsing PCEB systems known.