Discovery of a hot ultramassive rapidly rotating DBA White Dwarf

TL;DR

This paper reports the discovery of a nearby, massive, hot, and rapidly rotating white dwarf with stable photometric variability, likely formed from a binary white dwarf merger, providing insights into stellar evolution and supernova progenitors.

Contribution

The paper presents the first detailed characterization of a hot, ultramassive, rapidly rotating white dwarf with stable variability, suggesting a binary merger origin.

Findings

White dwarf has a mass of 1.33 solar masses.

It exhibits stable photometric variability with a period of 353.456 seconds.

The white dwarf's properties imply a binary merger origin.

Abstract

We report the discovery of a nearby massive white dwarf with He-H atmosphere. The white dwarf is located at a distance of $74.5\pm0.9$ pc. Its radius, mass, effective temperature, H/He ratio and age are $R=2500\pm100$ km, $M=1.33\pm0.01$ $\rm M_{\odot}$, $T_{\mathrm{eff}}=31200\pm 1200$ K, ${\mathrm{H/He}}\sim0.1$ and $330\pm40$ Myr, respectively. The observed spectrum is redshifted by $V_{\mathrm{r}}=+240\pm15$ km s$^{-1},$ which is mostly attributed to the gravitational redshift. The white dwarf shows a regular stable photometric variability with amplitude $\Delta g\approx0.06^{\mathrm{m}}$ 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 at the Carboniferous Period of the Earth history.