We present the discovery with WISE of a significant infrared excess associated with the eclipsing post-common envelope binary SDSSJ 030308.35+005443.7 , the first excess discovered around a non-interacting white dwarf+main sequence M dwarf binary .
The spectral energy distribution of the white dwarf+M dwarf companion shows significant excess longwards of 3µm .
A T _ { eff } of 8940 K for the white dwarf is consistent with a cooling age > 2 Gyr , implying that the excess may be due to a recently formed circumbinary dust disk of material that extends from the tidal truncation radius of the binary at 1.96 R _ { \odot } out to < 0.8 AU , with a total mass of \sim 10 ^ { 20 } g. We also construct WISE and follow-up ground-based near-infrared light curves of the system , and find variability in the K band that appears to be in phase with ellipsoidal variations observed in the visible .
The presence of dust might be due to a ) material being generated by the destruction of small rocky bodies that are being perturbed by an unseen planetary system or b ) dust condensing from the companion ’ s wind .
The high inclination of this system , and the presence of dust , make it an attractive target for M dwarf transit surveys and long term photometric monitoring .