Polarization and the envelopes of B(e) supergiants in the Magellanic Clouds

Abstract

We report optical linear polarization observations of nine B[e] supergiants in the Magellanic Clouds. Several of them have large intrinsic polarizations. The data are consistent with non-spherically symmetric envelopes, around the B[e] stars, that possess a range of intrinsic polarizations. Comparison of the polarimetric data with the viewing aspect, inferred from the spectroscopy of the individual objects, agrees with this interpretation. The polarization correlates best with the infrared excess due to dust, suggesting the latter as the cause of most of the polarization. We cannot find, using the available data, a statistically significant difference between the polarization distributions of Galactic and Magellanic B[e] stars. There are some indications that the detection of CO emission from the objects may also depend upon their inclination. Comparison of our data with previous polarimetric data, recovered from the literature for four stars, seems to indicate that the envelopes are stable. Spectropolarimetry of selected objects should provide further insight into their envelopes.