IW And is a Z Cam-Type Dwarf Nova

Abstract

IW And was discovered as a unique blue variable, which spends 72% of time in "inactive" state, and was only occasionally observed in bright or faint states. Although the past spectroscopy confirmed that the object is a cataclysmic variable (CV), the object has been regarded as significantly different from the known subclasses of CVs. We observed IW And on 55 nights between 2001 December 6 and 2002 March 25. These observations clearly indicate that the object is a Z Cam-type dwarf nova. The duty cycle of standstill in IW And is exceptionally high among Z Cam stars. IW And is apparently the first object to fill the gap between classical Z Cam stars and novalike (NL) stars.