Structure and fate of binary WR stars: Clues from spectropolarimetry

TL;DR

This paper explores how spectropolarimetry of binary Wolf-Rayet stars reveals their wind structures and helps identify potential gamma-ray burst progenitors through polarization signatures.

Contribution

It introduces a novel binary line-effect method using spectropolarimetry to detect rapidly rotating WR stars in binaries, aiding in understanding their evolution and GRB potential.

Findings

Polarimetric signatures vary with orbital phase.

Far-scattering lines can indicate rapid rotation.

Method may identify GRB progenitors in binaries.

Abstract

Because most massive stars have been or will be affected by a companion during the course of their evolution, we cannot afford to neglect binaries when discussing the progenitors of supernovae and GRBs. Analyzing linear polarization in the emission lines of close binary systems allows us to probe the structures of these systems' winds and mass flows, making it possible to map the complex morphologies of the mass loss and mass transfer structures that shape their subsequent evolution. In Wolf-Rayet (WR) binaries, line polarization variations with orbital phase distinguish polarimetric signatures arising from lines that scatter near the stars from those that scatter far from the orbital plane. These far-scattering lines may form the basis for a "binary line-effect method" of identifying rapidly rotating WR stars (and hence GRB progenitor candidates) in binary systems.