  RXTE made 5 X-ray observations of the magnetic accretor GK Per during its
1996 outburst, recording a count rate of ten times the quiescent level. The
351-s spin pulse shows a deep, nearly sinusoidal modulation, in contrast to the
weaker, double-humped profile of quiescence. The spectrum shows absorption
increased by two orders of magnitude over quiescence. We explain these
differences in terms of the changing accretion geometry as the outbursting disc
forces the magnetosphere inwards, and discuss the 5000-s X-ray QPOs seen during
GK Per's outbursts.
