ACCRETION-DISK REFLECTION OF THE BIPOLAR WIND OF BI CRUCIS

Linear spectropolarimetry of the symbiotic Mira BI Crucis is presented that demonstrates that the object is intrinsically polarized, confirm ing previous photopolarimetric observations. It is shown that this int rinsic polarization is perpendicular to the object's extended bipolar nebula. The blue wing of the Her emission line is unpolarized, while t he weaker red wing shows significant polarization. We propose that thi s spectropolarimetric structure is the result of scattering of the fas t bipolar wind flux in the collimating accretion disk-the polarized fl ux is a 'reflection' of the bipolar wind. We construct a numerical mod el of the scattering geometry which demonstrates that this scenario is capable of reproducing the observed spectropolarimetric structure.