Changing Supercycle of the ER UMa-Type Star V1159 Ori

We examined the VSNET light curve of the ER UMa-type star V1159 Ori. Wedetected a large variation of the supercycle (the interval between successivesuperoutbursts) between extremes of 44.6 and 53.3 d. The outburst activity wasalso found to decrease when the supercycle was long. The observed variation ofthe supercycle corresponds to a variation of ~40 % of the mass-transfer ratefrom the secondary star, totally unexpected for this class of objects. We alsodetected a hint of ~1800 d periodicity in the variation, whose period is closeto what has been suggested for solar-type cycles for cataclysmic variables(CVs). If this periodicity is caused by the magnetic activity of the secondarystar, this detection constitutes the first clear evidence of continuingmagnetic activity in CV evolution, even after crossing the period gap. Thisactivity may partly explain still poorly understood origins of the highmass-transfer rates in ER UMa-type stars.Comment: 4 pages, 3 figures, using a non-standard style fil