V485 Centauri: the Shortest Period SU UMa Star

Abstract

We report CCD observations of the dwarf nova V485~Cen during its 1997 superoutburst. The long lasting outburst with characteristic slope, brightness dip and presence of clear superhumps give evidence that V485 Cen belongs to the group of SU UMa-type variables. The superhump period is equal to 0.042156 +/- 0.000004 d (60.7 min). Thus V485 Cen has the shortest known period among SU UMa-type stars, with a period as much as 25% shorter than previously known objects. The analysis of times of superhump maxima gives clear evidence for the increase of superhump period with P(dot)=28.3*10^{-5}. This fact confirms the hypothesis that the shortest periods SU UMa variables contrary to other stars of this type have positive values of P(dot).