Superhumps and grazing eclipses in the dwarf nova BG Arietis

We report unfiltered photometry of BG Arietis (= SDSS J015151.87+140047.2) in 2009 and 2010 which shows the presence of superhumps with peak-to-peak amplitude of up to 0.36 magnitudes showing this to be an SU UMa type dwarf nova. The outburst amplitude was 5.1 magnitudes above a mean quiescence magnitude of 19.9. The 2010 event lasted at least 20 days during which we observed a precursor outburst which was immediately followed by a superoutburst. Modulations were observed during the rise to superoutburst with a period approximately half Porb. The mean superhump period during the plateau phase was Psh = 0.0849(6) d, representing a superhump period excess epsilon = 0.030(7). We also observed small eclipses of depth 0.06 to 0.13 magnitude and FWHM duration of ~12 mins (ΔΦ1/2 = 0.10), which we interpret as grazing eclipses of the accretion disc. The 2009 superoutburst was less well observed, especially in the early stages, so we cannot tell whether there was a precursor outburst. The mean superhump period during the plateau was Psh = 0.0851(4) d, but towards the end of the plateau it suddenly decreased to Psh = 0.0845(11) d. Small eclipses were also observed.

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