The period-gap cataclysmic variable CzeV404 Her: A link between SW Sex and SU UMa systems

Abstract

Context. We present a new study of the eclipsing cataclysmic variable CzeV404 Her (Porb = 0.098 d) that is located in the period gap. Aims. This report determines the origin of the object and the system parameters and probes the accretion flow structure of the system. Methods. We conducted simultaneous time-resolved photometric and spectroscopic observations of CzeV404 Her. We applied our light-curve modelling techniques and the Doppler tomography method to determine the system parameters and analyse the structure of the accretion disk. Results. We found that the system has a massive white dwarf MWD = 1.00(2) M⊙, a mass ratio of q = 0.16, and a relatively hot secondary with an effective temperature T2 = 4100(50) K. The system inclination is i = 78.8°. The accretion disk spreads out to the tidal limitation radius and has an extended hot spot or line region. The hot spot or line is hotter than the remaining outer part of the disk in quiescence or in intermediate state, but does not stand out completely from the disk flux in (super)outbursts. Conclusions. We claim that this object represents a link between two distinct classes of SU UMa-type and SW Sex-type cataclysmic variables. The accretion flow structure in the disk corresponds to the SW Sex systems, but the physical conditions inside the disk fit the behaviour of SU UMa-type objects.