  We present a spectrophotometric study of short-term optical variability in
the quiescent black hole X-ray transient V404 Cyg focusing on two nights of
Halpha spectroscopy. We find significant variability, with both the Halpha line
and the continuum varying in a correlated way. This includes both dramatic
flares lasting a few hours in which the line flux nearly doubles and
lower-level flickering. The strongest flares involve development of asymmetry
in the line profile, with the red wing usually strongest independent of orbital
phase. Based on the line profile changes during the flares, we conclude that
the most likely origin for the variability is variable photoionisation by the
central source.
