2004MNRAS.355....1F

We present high-speed, three-colour photometry of the faint eclipsing cataclysmic variables XZ Eri and DV UMa. We determine the system parameters through two techniques: first, timings of the eclipse contact phases of the white dwarf and bright-spot using the derivative of the light curve; and secondly, a parametrized model of the eclipse fitted to the observed light curve by χ² minimization. For both objects, we prefer the latter method, as it is less affected by photon noise and rapid flickering. For XZ Eri we obtain a mass ratio q= 0.1098±0.0017 and an orbital inclination. For DV UMa we derive figures of q= 0.1506±0.0009 and. The secondary star in XZ Eri has a very low mass M_r/M_☉= 0.0842±0.0024, placing it close to the upper limit on the mass of a brown dwarf.