Optical linear polarization measurements of WR massive binary and single stars

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We present optical (UBVRI) linear polarimetric observations of 8 Wolf-Rayet (WR) massive binaries and single stars. We have corrected the observed values for the interstellar extinction and polarization by the interstellar medium to obtain the intrinsic polarization and position angle. We find three highly polarization stars between 5% and 10% (WR1, WR5 and WR146), three between 3% and 4% (WR2, WR3 and WR4), and two between 1% and 2% (WR137 and WR140). Moreover, 5 stars show increasing degree of polarization to shorter wavelengths (e.g WR 146) indicative with asymmetric circumstellar envelope and 3 have nearly constant polarization within the errors (e.g WR 140).