Precise Ages of Field Stars From White Dwarf Companions in Gaia DR2

TL;DR

This study derives precise ages for 3,551 white dwarf binary systems using Gaia DR2 data, enabling accurate age estimates for their main sequence companions, which are otherwise difficult to determine.

Contribution

It introduces a method to determine system ages and progenitor properties for a large sample of white dwarf binaries, improving age precision and validation techniques.

Findings

Median age precision of 20% for 3,551 WDs

System ages mostly between 1-6 Gyr

Validated ages against clusters and WD-WD binaries

Abstract

We analyze 4\,050 wide binary star systems involving a white dwarf (WD) and usually a main sequence (MS) star, drawn from the large sample assembled by \citet[][hereafter, T20]{Tian_2020}. Using the modeling code BASE-9, we determine the system's ages, the WD progenitors' ZAMS masses, the extinction values ($A_V$), and the distance moduli. Discarding the cases with poor age convergences, we obtain ages for 3\,551 WDs, with a median age precision of $\sigma_{\tau}/\tau = 20$\%, and system ages typically in the range of 1-6 Gyr. We validated these ages against the very few known clusters and through cross-validation of 236 WD-WD binaries. Under the assumption that the components are co-eval in a binary system, this provides precise age constraints on the usually low-mass MS companions, mostly inaccessible by any other means.