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

TL;DR

This paper analyzes 1.5 years of Kepler data on V447 Lyr, revealing eclipses, outburst patterns, and disk behavior, providing insights into the accretion processes of this eclipsing U Gem-type dwarf nova.

Contribution

First detection of eclipses in V447 Lyr, a U Gem dwarf nova, and analysis of its outburst behavior and disk dynamics using Kepler observations.

Findings

V447 Lyr is the first dwarf nova in Kepler field with observed eclipses.

Outbursts are triggered by short outbursts, similar to SU UMa super-outbursts.

Eclipse width and phase vary with outburst state, indicating disk size changes.

Abstract

We present the results of an analysis of 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.