Kilo-Second Quasi-Periodic Oscillations in the Cataclysmic Variable DW Cancri

Our photometric monitoring revealed that DW Cnc, which was originallyclassified as a dwarf nova (V=15--17.5), remained at a bright state ofRc=14.68+/-0.07 for 61 days. In conjunction with optical spectra lacking astrong He II emission line, we propose that the object is not a dwarf nova, buta non-magnetic nova-like variable. Throughout our monitoring, the object showedstrong quasi-periodic oscillations (QPOs) with amplitudes reaching about 0.3mag. Our period analysis yielded a power spectrum with two peaks of QPOs, whosecenter periods are 37.5+/-0.1 and 73.4+/-0.4 min and, furthermore, with asignificant power in frequencies lower than the QPOs. DW Cnc is a uniquecataclysmic variable in which kilo-second QPOs were continuously detected for61 days. We propose two possible interpretations of DW Cnc: (i) A permanentsuperhumper below the period minimum of hydrogen-rich cataclysmic variables.(ii) A nova-like variable having an orbital period over 3 hours. In this case,the QPOs may be caused by trapped disk oscillations.Comment: 6 pages, 4 figures, PASJ in pres