CCD Photometry of KR Aurigae in 1996--2005

KR Aur is a well-known cataclysmic variable star, discovered by M. Popova in 1960. It is an interacting close-binary system with a period of 4 hours, consisting of a white dwarf with mass about 0.6–0.7 M⊙ and a secondary red dwarf with mass about 0.35–0.40 M⊙ (spectral class M2V–M3V). The less massive component is filling up its Roche lobe and it is transferring mass to the compact primary star. An accretion disk is formed in the system and that disk radiates the predominant part of the emitted light in the stars normal state. This object is classified as anti-dwarf novae or VY Scl type star: usually the brightness of KR Aur is about 13 mag (with amplitude of 1 mag) in V , but occasionally mass transfer from the late-type star to the white dwarf appears to fade and the magnitude drops to 15–16 mag (intermediate state) or rarely to 18–19 mag (low state). The latest minimum of KR Aur was too long and too deep: it continued from 1994 (Antov et al. 1996) to 2001. We present photometric data obtained during the period 1996–2005 from a group of observers. The behaviour of the KR Aur light-curve was very unsteady: the brightness varied between intermediate and weak values.