Observations and optical light-curve analysis for the precataclysmic variable BE Ursae Majoris

We have acquired three-color observations of BE UMa, a precataclysmic eclipsing variable with a strong reflection effect. Using new photoelectric U BV data and archival photographic observations, we have refined the orbital period and demonstrated that the eclipse depth changes with wavelength. The photometric data are used to compute a model for the system. Computations show that the nuclear evolution time for the secondary is only slightly less than the time for the separation of the components to change due to the loss of orbital angular momentum. Therefore, the red dwarf in the BE UMa system will later fill its Roche lobe because of (1) the decrease in component separation due to the loss of energy and angular momentum via gravitational-wave radiation or the outflow of a magnetic stellar wind and (2) the increase in the red dwarf’s radius due to its nuclear evolution.