The total mass of the close, double degenerate (DA+DQ) system NLTT~16249

TL;DR

This study refines the properties of the close double white dwarf system NLTT 16249, revealing mass, temperature, and composition details, and suggests a common envelope origin for the binary.

Contribution

The paper provides new spectroscopic and atmospheric analyses of NLTT 16249, improving estimates of component masses, compositions, and evolutionary history.

Findings

The DQ white dwarf is up to 6% more massive than the DA companion.

Lower masses and temperatures are derived for both components compared to previous estimates.

The components are nearly coeval, likely formed through a single common envelope event.

Abstract

We revisit the binary and stellar properties of the double-degenerate system NLTT 16249. An analysis of new echelle spectra, supported by a joint study of a DQZ velocity template NLTT 44303, confirms the orbital period and constrains the mass ratio revealing a carbon-polluted DQ white dwarf that is up to ~6 percent more massive than its hydrogen-rich DA companion. Our new model atmosphere analysis of the DA and DQ components, constrained by an accurate Gaia parallax measurement that places the binary at a distance of 57.8 pc, reveals lower mass and temperature than previously estimated for both components, but with higher carbon and nitrogen abundances in the DQ atmosphere. The two components are nearly coeval and could have been generated following a single common envelope event.