Simulating the emission line radial velocity modulation in discless intermediate polars

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