Kepler Observations of V447 Lyr: An Eclipsing U Gem Cataclysmic Variable

Gavin Ramsay, John K. Cannizzo, Steve B. Howell, Matt A. Wood, Martin Still, Thomas Barclay, Alan Smale

Figure 4. The folded light curve obtained from data taken during the quiescent interval MJD=55687.0–55714.0, ie between outbursts SO4 and LO4 (see Table 2).


We present the results of an analysis of Kepler data covering 1.5 years of the dwarf nova V447 Lyr. We detect eclipses of the accretion disk by the mass donating secondary star every 3.74 hrs which is the binary orbital period. V447 Lyr is therefore the first dwarf nova in the Kepler field to show eclipses. We also detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem type dwarf nova. We show that the orbital phase of the mid-eclipse occurs earlier during outbursts compared to quiescence and that the width of the eclipse is greater during outburst. This suggests that the bright spot is more prominent during quiescence and that the disk is larger during outburst than quiescence. This is consistent with an expansion of the outer disk radius due to the presence of high viscosity material associated with the outburst, followed by a contraction in quiescence due to the accretion of low angular momentum material. We note that the long outbursts appear to be triggered by a short outburst, which is also observed in the super-outbursts of SU UMa dwarf novae as observed using Kepler.

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Last Revised: 2012 July 5th