Discovery of a hot ultramassive rapidly rotating DBA white dwarf

We report the discovery of a nearby massive white dwarf with He-H atmosphere. The white dwarf is located at a distance of 74.5 ± 0.9-=pc. Its radius, mass, effective temperature, H/He ratio, and age are R = 2500 ± 100-=km, M = 1.33 ± 0.01-= $\rm M_{\odot }$ , T_eff = 31-=200 ± 1200-=K, H/He ∼ 0.1, and 330 ± 40-=Myr, respectively. The observed spectrum is redshifted by V_r = +240 ± 15-=km-=s^-1, which is mostly attributed to the gravitational redshift. The white dwarf shows a regular stable photometric variability with amplitude Δg ≈ 0.06^m and period P = 353.456 s suggesting rapid rotation. This massive, hot, and rapidly rotating white dwarf is likely to originate from the merging of close binary white dwarf system that avoided explosion in a thermonuclear Type Ia supernova.