System parameters of three short-period cataclysmic variable stars

ABSTRACT Using photometric ULTRACAM observations of three new short-period cataclysmic variables (CVs), we model the primary eclipse light curves to extract orbital separation, masses, and radii their component stars. We find donor masses $0.060\pm 0.008\, {\rm M_\odot }$, $0.042\pm 0.001\, 0.004\, two being very low-mass sub-stellar donors, one within 2σ hydrogen burning limit. All systems lie close empirical evolutionary sequence that has emerged from last decade. briefly re-evaluate long-standing discrepancy between observed mass radius data, theoretical CV tracks. By looking at difference in period each predicted by modelled sequences, qualitatively examine form excess angular momentum loss is missing models below gap. show indications grows importance relative gravitational losses as decreases. Detailed are necessary draw more quantitative conclusions future.