SPECKLE-MASKING IMAGING POLARIMETRY OF ETA-CARINAE - EVIDENCE FOR AN EQUATORIAL DISK

With our new speckle imaging polarimeter we have obtained the first po larimetric images with sub-arcsecond resolution of the Luminous Blue V ariable eta Carinae in the H alpha line. The polarization patterns at the 3'' scale match well earlier conventional imaging photometry and c an be interpreted as Mie scattering. In crosscorrelation-centered imag es we detected in polarized light a bar in the NE part of the equatori al plane of eta Carinae. High-resolution 0.11'' polarimetric speckle r econstructions reveal a compact structure elongated in the same direct ion which is consistent, in degree and position angle of the polarisat ion, with the presence of a circumstellar, equatorial disk. The degree of polarization of the previously discovered speckle objects and the Ho arm is relatively low (similar to 10%) and thus may indicate a posi tion within the equatorial plane. We also discovered a highly polarize d (20% - 40%) bipolar structure along the major axis of the Homunculus nebula which can be traced down to the sub-arcsecond scale. This is p robably the inner part of a bipolar outflow into the Homanculus.