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

We report CCD photometry of the dwarf nova BF Ara in quiescence carried out throughout fifteen consecutive nights. Light curve in this interval is dominated by a large amplitude (≈0.8 mag), two period modulations. Higher amplitude signal has a period of 0.082159(4) days, which was increasing at the rate of P/Psh=3.8(3)×10-5. Weaker and stable second signal has a period of 0.084176(21) days. Because the superhump period of BF Ara is equal to 0.08797(1) days, the first modulation is interpreted as quiescent negative superhump arising from retrograde precession of titled accretion disk and the latter one as the orbital period of the binary. The respective period excess and defect are ε=4.51%±0.03% and ε-=-2.44%±0.02%. Thus BF Ara is yet another in-the-gap nova with mass ratio of q≈0.21.