From long-term photometry of a VY Scl-type star , V425 Cas , between 1998 and 2000 , we discovered a short-term , large-amplitude ( up to 1.5 mag ) variations .
The variation was well represented by a single period of 2.65 d. The large amplitude and the profile of the folded light curve suggest that the dwarf nova-type disk instability is responsible for this variation .
The shortness of the period is unprecedented in hydrogen-rich cataclysmic variables .
Given the recent emerging evidence that the irradiation from white dwarfs in VY Scl-type systems affect their light behavior , we propose a possibility that this unique variation in V425 Cas can be explained by the combination of the dwarf nova-type disk instability and irradiation .
Similar short-period “ outbursts ” have been known in X-ray transients ( V518 Per ) , and helium cataclysmic variables ( CR Boo and V803 Cen ) .
We discuss the possibility that these phenomena have a common origin to the unique variation in V425 Cas .