抄録
The secular variation in the interval of outbursts in the following six Z Cam-type dwarf novae (including the
subtype IW And-type) is investigated: Z Cam, RX And, AH Her, HL CMa, SY Cnc, andWWCet. An analysis using
the O − C diagram shows that the interval of outbursts is not steady in one system. The outburst properties before
standstill are the decrease in outburst interval, enhancement of the magnitude in quiescence, and disappearance of
the long outburst. Meanwhile, several objects have at least two typical intervals of outbursts. These characteristics
are difficult to be explained only by the variation in mass transfer from the secondary.
