Temporal polarization variations of Be stars. IV. The polarimetric behaviour of sigma Orionis E.

Although photometric and spectrometric studies strongly indicate the presence of two absorbing clouds co-rotating with the star, the effectiveness of a simplistic model (point source/point scatterer) for fitting polarimetric data is demonstrated for σ Ori E. Analysis of B-band polarization data confirms that scattering regions or atmospheric bulges lie in the stellar equatorial plane and that the same clouds produce the two eclipses clearly seen in the light curve. The model fit provides a stellar inclination (i) = 80°±6° and shows that the star rotates from right to left. In combination with magnetographic data, this value of i gives the obliquity of the magnetic pole ≡50°, with the polar field strength 11600 Gauss±1360 Gauss. The information deduced from polarimetry confirms that the atmospheric bulges are concentrated at the intersections of the stellar rotational equator and magnetic equator, but with the latter not being a great circle.