The Initial-Final Mass-Relation

Evolution from the main sequence to the white dwarf phase involves a star losing a significant fraction of its mass during the giant stages of stellar evolution. The precise mapping between the mass a star is born with to the mass it has when it begins cooling as a white dwarf is called the Initial-Final Mass-Relation (IFMR).

The importance of the IFMR is wide reaching in astrophysics because of its direct link to mass loss, thus placing important constraints on stellar evolution itself as well as chemical enrichment of the Galaxy. However, the IFMR is challenging to probe numerically due to the sensitivity of models to input physics. It can however be measured semi-empirically.

The most common approach to measure the IFMR is to observe white dwarfs in clusters where the cluster age can be measured from the turnoff in the colour-magnitude diagram, and white dwarf cooling ages and masses can be determined from their spectroscopy. The pre-white dwarf lifetime can then be used to infer the initial mass of the white dwarf progenitor.

More recently Andrews et al. (2015) demonstrated that wide double white dwarf binaries can also be used to constrain the IFMR. This is because both components should have formed together but evolved independently. Measuring the masses and cooling ages of both components therefore constrains which possible choices of IFMR could have produced the binary, assuming that both have the same total age. Using a Bayesian framework, a large sample of wide double white dwarfs can be used to provide tight constraints on the IFMR.

I am currently applying the work of Andrews et al. (2015) to a large population of double white dwarfs identified through Gaia, while also extending the Bayesian framework to detect to outliers and underestimated systematic uncertainties.