SPECTRUM OF THE INVISIBLE COMPANION OF Z-CANIS-MAJORIS REVEALED IN POLARIZED-LIGHT

Optical spectropolarimetry of the FU Orionis variable Z CMa in 1991-19 92 shows larger polarization in the emission lines than in the continu um. The intensity spectrum at this time has absorption lines with some narrow weak emission. The polarized flux spectrum appears similar to an intensity spectrum of Z CMa obtained in 1987 when it was approximat ely 0.9 mag brighter at V and showed strong emission lines. We argue t hat the primary component of the Z CMa binary is an emission line sour ce, perhaps an Ae/Be star, that varies at V by 1-3 mag and was respons ible for the 1987 outburst. The primary is mostly obscured from view b y an asymmetrical distribution of dust which polarizes the light scatt ered into our line of sight. The 'secondary, a normal FU Orionis varia ble, is seen more directly, and therefore contributes a large amount o f unpolarized flux, about 80% of the total optical flux. Most of the p olarization is intrinsic to the system and oriented perpendicular to t he jet axis. We propose that independent variations in the brightness of both sources are responsible for the appearance and disappearance o f a narrow emission line spectrum on the broader FU Orionis absorption line spectrum.