Mass Constraints from Eclipse Timing in Double White Dwarf Binaries

TL;DR

This paper shows that eclipse timing in double white dwarf binaries can be used to accurately measure individual stellar masses, leveraging effects similar to pulsar timing delays, with potential for high precision using modern telescopes.

Contribution

It introduces a method to determine white dwarf masses through eclipse timing delays, extending pulsar timing techniques to binary white dwarf systems.

Findings

Eclipse timing differences can constrain individual WD masses.

Measurement uncertainties below 0.1 seconds enable mass determinations with 0.02 Msun accuracy.

The method is most effective in wide binaries with non-equal mass ratios.

Abstract

I demonstrate that an effect similar to the Roemer delay, familiar from timing radio pulsars, should be detectable in the first eclipsing double white dwarf (WD) binary, NLTT 11748. By measuring the difference of the time between the secondary and primary eclipses from one-half period (4.6 s), one can determine the physical size of the orbit and hence constrain the masses of the individual WDs. A measurement with uncertainty <0.1 s---possible with modern large telescopes---will determine the individual masses to +/-0.02 Msun when combined with good-quality (<1 km/s) radial velocity data, although the eccentricity must also be known to high accuracy (+/- 1e-3). Mass constraints improve as P^{-1/2} (where P is the orbital period), so this works best in wide binaries and should be detectable even for non-degenerate stars, but such constraints require the mass ratio to differ from one and undistorted orbits.