Magnitude-limited catalogue of unresolved white dwarf-main sequence binaries from Gaia DR3

Context. Binary stars containing a white dwarf and a main sequence star (WDMS binaries) can be used to study a wide range of aspects of stellar astrophysics.

Aims. We built a magnitude-limited sample of unresolved WDMS binaries from Gaia DR3 to enlarge these studies.

Methods. We looked for WDMS with available spectra whose location in the Gaia colour-magnitude diagram bridges the gap between the evolutionary sequences of single white dwarfs (WDs) and the MS. To exclude spurious sources, we applied quality cuts on the Gaia photometry and astrometry and we fit the SED (spectral energy distribution) of the objects with VOSA (Virtual Observatory SED Analyser) to exclude single sources. We further cleaned the sample via visual inspection of the Gaia spectra and publicly available images of the objects. We re-fit the SEDs of the finally selected WDMS with VOSA using composite models to measure their stellar parameters and we searched for eclipsing systems by inspecting available ZTF and CRTS light curves.

Results. The catalogue consists of 1312 WDMS and we manage to derive stellar parameters for 435. This is because most WDMS are dominated by the MS companions, making it hard to derive parameters for the WDs. We also identified 67 eclipsing systems and estimated a lower limit to the completeness of the sample to be ≃50% (≃5% if we consider that not all WDMS in the studied region have Gaia spectra).

Conclusions. Our catalogue increases the volume-limited sample we presented in our previous work by one order of magnitude. Despite the fact that the sample is incomplete and suffers from heavy observational biases, it is well characterised. Thus, it can be used to further constrain binary evolution by comparing the observed properties to those from synthetic samples obtained by modelling the WDMS population in the Galaxy, while taking into account all selection effects.