The evolutionary history of ultra-compact accreting binaries: I. Chemical abundances and the formation channel of the eclipsing AM CVn system ZTF J225237.05-051917.4 from HST spectroscopy

Context. AM Canum Venaticorum (AM CVn) stars are ultra-compact binary systems composed of a white dwarf primary accreting from a hydrogen-deficient donor. They play a crucial role in astrophysics as potential progenitors of Type Ia supernovae and as labor