SIMULATING THE EMISSION-LINE RADIAL-VELOCITY MODULATION IN DISCLESS INTERMEDIATE POLARS

A code has been developed which simulates the emission line radial vel ocity modulation expected in a discless intermediate polar, where the bulk of the accretion flow flips from one magnetic pole to the other t wice every beat cycle. The situation is found to produce a radial velo city curve which exhibits a modulation at the beat period, although th is is not strictly periodic in that it is modified by an intrinsic und erlying orbital modulation; i.e., the morphology of the beat modulatio n over one beat cycle depends on the orbital phase. Interestingly, it is found that, when the resultant velocity curve over one orbital cycl e is folded on the beat period and binned coarsely, a quasi-sinusoidal velocity profile can be reproduced, depending on the values chosen fo r the various free parameters. An important implication of this result is that the spin period of BG Canis Minoris could indeed be 847 s, an d is not necessarily 913 s as we had previously concluded. The model i s also capable of reproducing the modulation seen in the newly discove red system RXJ1712.6-2414.