1999A&A...347..590C

High accuracy polarimetric observations made on three nights are reported for the Herbig Be star HD100546 revealing changes both in the linear and circular components. Continuous monitoring over windows ∼2hrs reveal no variation or secular change in p at levels ∼0.0002 but night-to-night changes ∼0.0010 are clearly recorded. The p(V)/p(B) ratio indicates an interstellar polarization component. Accounting for this by consideration of field stars does not, however, provide an intrinsic value for this ratio that is explained by electron scattering and it is concluded that the basic polarigenic mechanism is scattering by dust within the circumstellar environment.