Ultracompact mass-transferring WD binaries

In this paper, we provide an overview of the literature background and describe recent breakthroughs, open questions, and connections to other fields. This overview is intended to provide a starting point for researchers who are relatively new to the fields of ultracompact binaries or AM CVn-type binaries.

We define the scope of the catalogue (the criteria for inclusion) and describe its format and contents (what data have been included for each target). We also summarise the observed properties of the known mass-transferring ultracompact binaries, including their orbital periods and component stellar masses and radii. The catalogue presented here aims to provide a central resource to enable researchers to track the current status of the known sample.