Accurate Masses for the Primary and Secondary in the Eclipsing White Dwarf Binary NLTT 11748

TL;DR

This paper presents precise measurements of the primary and secondary masses in the eclipsing white dwarf binary NLTT 11748, revealing system parameters and evolutionary predictions based on spectroscopic and eclipse data.

Contribution

The study provides the first detailed mass and temperature measurements for NLTT 11748, including the primary's properties and the secondary's inferred mass, advancing understanding of such binary systems.

Findings

Primary mass: 0.18 Msol

Secondary mass: 0.76 Msol

Merger time: 7.2 Gyr

Abstract

We measure the radial velocity curve of the eclipsing detached white dwarf binary NLTT 11748. The primary exhibits velocity variations with a semi-amplitude of 273 km/s and an orbital period of 5.641 hr. We do not detect any spectral features from the secondary star, or any spectral changes during the secondary eclipse. We use our composite spectrum to constrain the temperature and surface gravity of the primary to be Teff = 8690 (140) K and log g = 6.54 (0.05), which correspond to a mass of 0.18 Msol. For an inclination angle of 89.9 deg. derived from the eclipse modeling, the mass function requires a 0.76 Msol companion. The merger time for the system is 7.2 Gyr. However, due to the extreme mass ratio of 0.24, the binary will most likely create an AM CVn system instead of a merger.