Curious Variables Experiment (CURVE). Three Periodicities of BF Ara

Abstract

We report CCD photometry of the dwarf nova BF Ara throughout fifteen consecutive nights in quiescence. Light curve in this interval is dominated by a large amplitude around 0.8 mag modulation consisting two periods. Higher amplitude signal is characterized by period of 0.082159(4) days, which was increasing at the rate of dotP/Psh = 3.8(3)* 10^{-5}. Weaker and stable signal has period of 0.084176(21) days. Knowing the superhump period of BF Ara determined by Kato et al. (2003) and equal to 0.08797(1) days, the first modulation is interpreted as quiescent negative superhump arising from retrograde precesion of titled accretion disk and the latter one as an orbital period of the binary. The respective period excess and defect are epsilon_+ = 4.51% +/- 0.03% and epsilon_- = -2.44% +/- 0.02%. Thus BF Ara is yet another in-the-gap nova with mass ratio q of around 0.21.