A massive ONe-core white dwarf
In August 2026, a manuscript led by graduate student and BUWD member Stefan Arseneau (Arseneau, Hermes, Chandra, et al. 2026) was published with an exceptionally cool test of the core composition of a massive (1.226 solar mass) white dwarf. Spectroscopy from 8.2- and 6.5-meter telescopes helped measure the velocity of this star relative to its wide binary companion. The mass of this compact object has bent space so much that light is redshifted by more than 170 km/s from its surface! This is more in line with predictions from an oxygen-neon core white dwarf, compared to a carbon-oxygen white dwarf. The manuscript has been accepted in The Astrophysical Journal.