Left: Hα and Mg Iλ5170 emission lines derived from the spectropolarimetry of 31 Dec 2008, with the neighboring continuum subtracted and shown twice for better visibility. Center: corresponding Doppler maps computed by the maximum entropy method MEM. The overlays show the Roche lobes of the secondary for the best bloated model of Sect. 7.5. Top right: the first orbit shows the orbital flux variations of the Mg I line (blue) and the narrow component of Hα (green). The second orbit shows the Hα flux and its mirror image around ϕ = 0.5 (see text). Bottom right: radial velocity curves of the MgI line (blue), the narrow Hα component (green), and the broad Hα component (crosses). A typical error bar for the broad line is shown in the lower left.