With less powerful magnetic fields on the primaries, synchronism cannot be achieved. This opens the way for a multitude of periodic phenomena and generates the class of magnetic CVs known as intermediate polars (IPs).

Historical Development

Charles et al. (1979) identified the X-ray source 2A0526–328 as a thirteenth magnitude star with a spectrum like AM Her but lacking detectable polarization; this was the first CV to be discovered by means of its X-ray emission. Photometry (Motch 1981) and spectroscopy (Hutchings et al. 1981a) revealed an orbital period (from RV modulation) of 5h 29.2 min and a photometric period of 5h 11.5min. The beat period between these, viz. 4.024 d, was also present in the light curve.

TV Col (as 2A0525–328 was designated) has turned out to be more complicated than even those initial observations suggested, so although Hutchings et al. proposed the correct basic model for the system, it is now applied to TV Col in a different manner (see below). For simplicity we will therefore move attention to the case history of AO Psc, which was being studied almost at the same time as TV Col.

The X-ray source H2252–035 was identified with a thirteenth magnitude previously unrecognized variable (later designated AO Psc) by Griffiths et al. (1980). Its spectrum resembled a DN at quiescence and photometry showed an orbital modulation of 3.6 h with a prominent 14.3 min periodic luminosity variation superimposed (Warner 1980; Patterson & Price 1980).