  We present spin-resolved spectroscopy of the accreting white dwarf binary
V455 And. With a suggested spin period of only 67s, it has one of the fastest
spinning white dwarfs known. To study the spectral variability on the spin
period of the white dwarf, we observed V455 And with 2s integration times,
which is significantly shorter than the spin rate of the white dwarf. To
achieve this cadence, we used the blue arm of the ISIS spectrograph at the
4.2-m William Herschel Telescope, equipped with an electron multiplying CCD
(EMCCD). Strong coherent signals were detected in our time series, which lead
to a robust determination of the spin period of the white dwarf (Pspin=67.619
+/- 0.002 s). Folding the spectra on the white dwarf spin period uncovered very
complex emission line variations in Hgamma, He I 4472 and He II 4686. We
attribute the observed spin phase dependence of the emission line shape to the
presence of magnetically controlled accretion onto the white dwarf via
accretion curtains, consistent with an intermediate polar type system. We are,
however, not aware of any specific model that can quantitatively explain the
complex velocity variations we detect in our observations. The orbital
variations in the spectral lines indicate that the accretion disc of V455 And
is rather structureless, contrary to the disc of the prototype of the
intermediate polars, DQ Her. This work demonstrates the potential of electron
multiplying CCDs to observe faint targets at high cadence, as readout noise
would make such a study impossible with conventional CCDs.
