A GINGA observation of FO AQR : discless accretion and multiple emission components.

A 32-hr Ginga observation of the intermediate polar FO Aqr is analyzed. The power spectrum of the X-ray light curve, constructed by means of the 1D CLEAN algorithm, indicates strong modulation at the binary-orbital, white-dwarf spin and beat periods. It is inferred from the asymmetry between the positive and negative orbital sidebands of the spin frequency that the beat modulation cannot be caused by an amplitude modulation of the spin pulse and must be intrinsic to the source. It is demonstrated that the beat is unlikely to be due to a reaction effect and as a result can only arise in a diskless accretion geometry in which the majority of the accretion flow switches from one magnetic pole of the white dwarf to the other every half a beat cycle. The use of the CLEAN algorithm applied to a GINGA time series is demonstrated, and it is employed to separate the spin-modulated components of the X-ray flux. The resulting reconstructed pulse profiles are free of contamination by any other modulation and are described in terms of multiple emission components.