Period variation in the white-dwarf eclipsing binary BD + 160516

Photometric observations of eclipse contacts over the past 4.7 years (3300 cycles) are discussed, revealing systematic variations in the period which suggest active mass transfer in progress. The period is found to have increased and decreased over this interval, and current models are not adequate to account for such variations when one component is a white dwarf. Some new and improved data for the system are also discussed. (U.S.)