Program: GS-2021B-Q-312

The Universe is not old enough for white dwarfs less massive than 0.3 solar masses to have formed by single-star evolution. Yet, about a hundred of these so-called extremely-low mass white dwarfs (ELMs) are known. Their existence is explained by enhanced mass-loss in binary interactions, although there are still many issues with the theoretical modelling, requiring additional observational input. ELMs can also be strong gravitational wave sources: most verification systems for the upcoming LISA mission are ELM binaries, therefore studies of the ELM population also impact the future of multi-messenger astronomy. We have compiled the first all-sky catalogue of ELM candidates, with 415 objects within 350 pc, out of which only 20% already have spectroscopic observations. Here we request 45 hours in Gemini South to obtain spectra for 36 candidates. Combined with observations in other facilities, our plan is to finish observing the full 350pc sample in one year.