The closest extremely low-mass white dwarf to the Sun

Abstract

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 Teff ≈ 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 TESS light 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.