Program: GS-2022A-Q-310

The Galaxy is not old enough for a 0.3Msun white dwarf to have formed in isolation. Yet, about a hundred of these extremely-low mass white dwarfs are known. These objects can only be formed by binary interactions. However, there is currently no detailed understanding of the processes behind their formation and their interior structure, making observational input necessary. We are asking for spectroscopic follow-up of a sample of ELM candidates that where selected from Gaia DR2 and EDR3 data and that have also shown variability in their TESS light curve. This is needed to confirm their nature.