Spectropolarimetry of WR 113 and other WR + O binaries with SALT

Gamma-ray bursts (GRBs) are enigmatic events that allow us to obtain information about distant galaxies and exotic physics due to their high energy. The precise progenitors of GRBs are unknown, but supernovae produced by massive stars are the primary candidates. Like other massive stars, WR stars often occur in binaries, where interaction can affect their mass loss rates and provide the rapid rotation thought to be required for GRB production. The diagnostic tool of spectropolarimetry, along with the potentially eclipsing nature of a binary system, helps us to better characterize the CSM created by the stars' colliding winds. Thus, we can constrain mass loss rates, probe wind interactions, and infer rapid rotation. I present spectropolarimetric results for a sample of WR+O binary systems, obtained with the Robert Stobie Spectrograph at the South African Large Telescope, between April 2017 and October 2018. The precisely phased observations we obtain with RSS/SALT allow us to map both continuum and emission line polarization variations over the binary cycle, and so potentially reconstruct the shapes and locations of the emitting and scattering regions within the system. I discuss our initial findings and interpretations of the polarimetric variability in several of the sampled binary systems. I analyze one system in particular, the WC8d+O8-9IV binary WR 113 (CV Ser), in light of recently published models of the system, and discuss its status as a possible GRB progenitor.