We present the results of medium-resolution (Delta v approximate to 60 km s
(-1)) spectropolarimetric observations across H alpha of a sample of B[e] a
nd Herbig Be objects. A change in linear polarization across Hoc is detecte
d in a large fraction of the objects, with characteristics ranging from sim
ple depolarization in a couple of Herbig Be stars, to more complex behaviou
r in the probable post-main-sequence B[e] stars. H alpha in the spectra of
HD 37806 and 50138 each consist of a double-peaked polarized line and a sup
erposed unpolarized single emission peak, suggesting two distinct line-form
ing regions. Multiple observations of HD 45677 allow for the separation of
electron and dust scattering effects for the first time: the difference bet
ween derived intrinsic polarization angles of the two components indicates
that the dust scattering region is clumpy. Two unexpected results are the n
on-detections of H alpha polarization changes in omega Ori, where depolariz
ation has previously been detected, and in MWC 297, which exhibits source e
longation at radio wavelengths. In omega Ori time variability is probably r
esponsible such that the electron scattering disc of this star was much wea
kened at the time of observation. Two hypotheses are advanced that might ex
plain the MWC 297 result.
The general finding are that roughly half of the observed Herbig Be stars s
how polarization changes across H alpha, implying immediately that their io
nized envelopes are not spherically symmetric. This pattern, if confirmed b
y observations of a larger sample, could indicate that the non-detection ra
te is simply a consequence of sampling randomly oriented circumstellar disc
s able to scatter starlight within a few stellar radii. The deduced alignme
nt of the disc of HD 53367 with the local interstellar magnetic field sugge
sts an orderly star formation process in which the star 'remembers' the lar
ger scale magnetic field direction. The stars classified as B[e] stars all
show startling polarization changes across H alpha. The details in each cas
e are different, but the widely accepted concept of dense H alpha-emitting
equatorial discs around these objects is supported.