  The favoured progenitors of long-duration gamma-ray bursts (GRBs) are rapidly
rotating Wolf-Rayet (WR) stars. However, most Galactic WR stars are slow
rotators, as stellar winds are thought to remove angular momentum. This poses a
challenge to the collapsar model. Recent observations indicate that GRBs occur
predominately in low metallicity (Z) environments, which may resolve the
problem: lower Z leads to less mass loss, which may inhibit angular momentum
removal, allowing WR stars to remain rotating rapidly until collapse. We wish
to determine whether low Z WR stars rotate on average more rapidly than
Galactic WR stars, and perform a Very Large Telescope (VLT) linear
spectropolarimetry survey of WR stars in the low Z environment of the Large
Magellanic Cloud (LMC) and compare our results with the Galactic sample. We
find that only 2 out of 13 (i.e. 15%) of LMC WR stars show line polarization
effects, compared to a similarly low fraction of ~15-20% for Galactic WR stars.
The low incidence of line polarization effects in LMC WR stars suggests that
the threshold metallicity where significant differences in WR rotational
properties occur is below that of the LMC (Z ~ 0.5 Zsun), possibly constraining
GRB progenitor channels to this upper metallicity.
