Measuring the Initial-Final Mass-Relation using wide double white dwarf binaries from Gaia DR3

TL;DR

This study uses Gaia DR3 data and VLT observations of wide double white dwarf binaries to precisely measure the initial-final mass relation, extending Bayesian methods to account for outliers and identifying potential merger candidates.

Contribution

It introduces an extended Bayesian framework with a mixture model to robustly determine the IFMR from wide double white dwarfs, including outlier handling and new merger candidate identification.

Findings

The IFMR is well constrained for initial masses 1-5 Msun.

Outlier fraction in the sample is large but uncertain, around 59%.

Four systems are identified as potential merger candidates.

Abstract

The Initial-Final Mass-Relation (IFMR) maps the masses of main sequence stars to their white dwarf descendants. The most common approach to measure the IFMR has been to use white dwarfs in clusters. However, it has been shown that wide double white dwarfs can also be used to measure the IFMR using a Bayesian approach. We have observed a large sample of 90 Gaia double white dwarfs using FORS2 on the VLT. Considering 52 DA+DA, DA+DC, and DC+DC pairs, we applied our extended Bayesian framework to probe the IFMR in exquisite detail. Our monotonic IFMR is well constrained by our observations for initial masses of 1-5 Msun, with the range 1-4 Msun mostly constrained to a precision of 0.03 Msun or better. We add an important extension to the framework, using a Bayesian mixture-model to determine the IFMR robustly in the presence of systems departing from single star evolution. We find a large but uncertain outlier fraction of 59$\pm$21 percent, with outlier systems requiring an additional $0.70^{+0.40}_{-0.22}$ Gyr uncertainty in their cooling age differences. However, we find that this fraction is dominated by a few systems with massive components near 0.9 Msun, where we are most sensitive to outliers, but are also able to establish four systems as merger candidates