July 11-15, 2011
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Short-term spectroscopic variability of WC9 stars

Sébastien Desforges (Université de Montréal)

Nicole St-Louis (Université de Montréal)
André-Nicolas Chené (Universidad de Concepción)

It is well-known that most WC9 stars produce dust either persistently, periodically or episodically. For WC9 binaries, the dust origins in gas compressed regions that form when the two stellar winds collide and a shock cone is produced. But not all WC9 stars are known binaries. The origin of the dust in single WC9 stars is far from clear. Are some of these presumably single WC9 stars yet undetected binaries? Do they have Corotating Interaction Regions in their wind, which produce the required density enhancements for dust formation?
Here we present the results of a spectroscopic monitoring campaign in the optical wavelength region of nine WC9 stars that we have carried out at the El Leoncito Observatory in Argentina in May-June 2009. The stars in our sample are not known binaries but have been shown from previous studies to present short-term, large amplitude spectroscopic variability.
We confirm that large-scale, line-profile variability is indeed present for several stars in our sample with timescales shorter than ~1 day. In addition to showing the variations of the line profiles as a function of time, we will present radial velocity, equivalent width and skewness measurements for the major lines present in our spectra and show the results of periodicity searches in all these quantities. Our goal is to determine the origin of the spectroscopic variability (binary, CIR, presence of clumps in the wind) and to provide new insight into the origin of dust in such an inhospitable environment as a WR wind.
(to be confirmed by the SOC)