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S. Kafka, R.K. Honeycutt (Indiana University, Astronomy Department)
More than 9 years of V-band photometry for QQ Vul obtained by RoboScope--a 0.41-m robotic telescope equipped for unattended differential CCD stellar photometry--allows us to examine systematic changes in light curve features that are apparently due to self eclipses of the accretion poles of the white dwarf. We generally have only one data point each clear night at some random orbital phase, but the orbital lightcurve and its changes can nevertheless be studied when the data is grouped into intervals of several months.
We have isolated three distinguishing behaviors of the system, each having durations of several months to several years. In behavior 1, the phased light curve of the system is characterized by a single broad dip between orbital phases 0.6 to 0.9. In behavior 2 a second dip is added between phases 0.1 and 0.2; this is accompanied by a prominent decrease in the brightness of the system by about 0.5 in mag. Generally QQ Vul remains in one of these two behaviors for many months to years. The third behavior is a mixture of behaviors 1 and 2 with changes between the two that are faster than our approximately two-week resolution. We think these light curves represent alternations between one-pole and two-pole accretion. Two pole accretion for QQ Vul has been suggested from soft x-ray and UV observations. These optical variations show that the time scales for alternation can be established by regular ground-based monitoring.