  We have found the first convincing evidence for spiral structure in the
accretion disc of a close binary. The eclipsing dwarf nova binary IP Peg,
observed during the end phase of a rise to outburst, shows strong Balmer and
Helium emission lines in its spectra, with asymmetric double peaked velocity
profiles produced in the accretion disc around the white dwarf. To reveal the
two armed spiral on the accretion disc, we de-project the observed emission
line profiles onto a Doppler coordinate frame, a technique known as Doppler
tomography. The two armed spiral structure we see in the Doppler tomograms is
expected to form when the disc becomes sufficiently large in outburst so that
the tides induced by the secondary star can excite waves in the outer disc.
Such spiral waves have been predicted in studies of tidal effects in discs and
are fundamental in understanding the angular momentum budget of accretion
discs.
