2020MNRAS.495L.129K

We present the orbit and properties of 2MASS J050051.85-093054.9, establishing it as the closest (d ≃ 71 pc) extremely low-mass white dwarf to the Sun. We find that this star is hydrogen rich with T_eff~10 500 K, log g ≃ 5.9, and, following evolutionary models, has a mass of ≃0.17 M_☉. Independent analysis of radial velocity and Transiting Exoplanet Survey Satellite(TESS) photometric time series reveals an orbital period of ≃9.5 h. Its high velocity amplitude (K~144~km s^–1) produces a measurable Doppler beaming effect in the TESSlight curve with an amplitude of 1 mmag. The unseen companion is most likely a faint white dwarf. J0500-0930 belongs to a class of post-common envelope systems that will most likely merge through unstable mass transfer and in specific circumstances lead to Type Ia supernova explosions.