choices of $K_2$ and $q=M_2/M_1=K_1/K_2$ discussed further below.

The trailed emission of He[ii]{} shows a nice S-wave pattern which is consistent with the reported 0.1708 day photometric period (Cook et al. 2000; Patterson 2000). Most of the He[ii]{} emission originates from a localized region but there is also an underlying (double-peaked) disk component which is visible in the original data. On the other hand, the disk dominates the H$\alpha$ profile producing a ring of emission in the velocity map. We also note the regions of enhanced H$\alpha$ emission at about (-910,0) km s$^{-1}$ (consistent with the He[ii]{} S-wave) and $(-210,-730)$ km s$^{-1}$. The peak at the velocity origin (the center of mass) is due to the H$\alpha$ emission component at rest wavelength discussed in §3.2.

The bright emission region is typically associated with emission arising from the stream-disk interaction region or from the X-ray heated surface of the secondary (e.g. Smak 1985; Marsh, Robinson & Wood 1994; Casares et al. 1995ab; Harlaftis et al. 1996, 1997ab; Hynes et al. 2000a). Some SXTs also have low-velocity emission regions in their doppler maps, possibly associated with a magnetic propeller (Hynes et al. 2000a). Here, the velocity of $\sim 900$ km s$^{-1}$ makes 