A Predicted Astrometric Microlensing Event by a Nearby White Dwarf

TL;DR

This paper predicts an upcoming astrometric microlensing event caused by a nearby white dwarf, which could allow precise mass measurement and testing of white dwarf models using Gaia data.

Contribution

It identifies a specific white dwarf as a candidate for an astrometric microlensing event and forecasts the potential for Gaia to measure its mass with high accuracy.

Findings

Predicted closest approach on November 11, 2019

Maximum source position deviation of 2.8 mas

Potential 3% accuracy in white dwarf mass measurement

Abstract

We used the Tycho-Gaia Astrometric Solution catalogue, part of the Gaia Data Release 1, to search for candidate astrometric microlensing events expected to occur within the remaining lifetime of the Gaia satellite. Our search yielded one promising candidate. We predict that the nearby DQ type white dwarf LAWD 37 (WD 1142-645) will lens a background star and will reach closest approach on November 11th 2019 ($\pm$ 4 days) with impact parameter $380\pm10$ mas. This will produce an apparent maximum deviation of the source position of $2.8\pm0.1$ mas. In the most propitious circumstance, Gaia will be able to determine the mass of LAWD 37 to $\sim3\%$. This mass determination will provide an independent check on atmospheric models of white dwarfs with helium rich atmospheres, as well as tests of white dwarf mass radius relationships and evolutionary theory.