S 111 and the polarization of the B[e] supergiants in the Magellanic Clouds

Abstract

We have obtained linear polarization measurements of the Large Magellanic Cloud B(e) supergiant S 111 using optical imaging polarimetry. The intrinsic polarization found is consistent with the presence of an axisymmetric circumstellar envelope. We have additionally estimated the electron density for S 111 using data from the literature and revisited the correlation between polarization and envelope parameters of the B(e) supergiant stars using more recent IR calibration color data. The data suggest that the polarization can be indeed explained by electron scattering. We have used Monte Carlo codes to model the continuum polarization of the Magellanic B(e) supergiants. The results indicate that the electron density distribution in their envelopes is closer to a homogeneous distribution rather than an r 2 dependence. At the same time, the data are best tted by a spherical distribution with density contrast than a cylindrical distribution. The data and the model results support the idea of the presence of an equatorial disk and of the two-component wind model for the envelopes of the B(e) supergiants. Spectropolarimetry would help further our knowledge of these envelopes.