July 11-15, 2011
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Timeseries of High Resolution Linear Spectropolarimetric Observations of Wolf-Rayet Stars

Nicole St-Louis (Université de Montréal)

Wolf-Rayet (WR) stars with their hot, dense winds are known to show variable linear polarisation in continuum light. For WR+O binaries, the changes are periodic as they are a consequence of the O companion acting as an asymetric light source to the copious amounts of free electrons in the WR wind. For single WR stars, the continuum polarisation changes are random and thought to be cause by inhomogeneities in the WR wind.

In linear spectropolarisation, binary WR stars show depolarisation in spectral lines because the continuum light from the O star is polarised as it is scattered off the free electrons in the WR wind but the line radiation from the WR wind is unpolarised. But some SINGLE WR stars also show depolarisation in spectral lines. This is thought to be caused by some residual polarisation in the continuum due do a non-spherically symetric wind. For recombination lines, the light should not be polarised leading to depolarisation in spectral lines.

I will present a timeseries of CFHT-Espadons linear spectropolarimetric observations of two presumably single WR stars, known to have large-scale asymetries in their wind, WR 6 and WR134. Any variations in the shape of the line profile when observed in linearly polarised light would indicate either that the structured wind is rotating and that our point of view is changing or that the structured wind is evolving in time.

(to be confirmed by the SOC)