2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/7185We report on first results of computing synthetic spectra from H/He-poor accretion disks in ultracompact LMXBs. We aim at the determination of the chemical composition of the very low-mass donor star, which is the core of a former C/O white dwarf. The abundance analysis allows to draw conclusions on gravitational settling in WDs which is an important process affecting cooling times and pulsational g-mode periods.to be published in: Compact Binaries in the Galaxy and Beyond (IAU Coll. 194) 3 pages, 1 figureAstrophysicstext