CFHT UM2025 - Presentation Details
Abstract Details
Title: Linear spectropolarimetric variations across spectral lines of WR6 as a tracer of large-scale structure in its wind
Presenter: Luca Fabiani
Abstract:
The winds of WR stars exhibit two main forms of structure: stochastic small-scale clumping and large-scale organized patterns, the latter often linked to Corotating Interaction Regions (CIRs) driven by rotational modulation. WR6 is a prime example of such structured winds, showing strong variability with a 3.76-d period. Variation patterns are found to be stable over several weeks and then evolve in nature, which is often interpreted as the signature of CIRs shaping the wind dynamics. Spectropolarimetry is a powerful tool to investigate wind structures. I will present CFHT/Espadons observations obtained in 2009, 2010 and a new dataset over 20 days in 2024 that reveal periodic variability that support the CIR interpretation. Our data show significant linear polarization variations across several HeII lines and lines of other ions such as HeI, CIV, NIV and NV. These changes can be partly attributed to the dilution of continuum polarization by unpolarized line flux, but this mechanism alone cannot fully explain the observations. Additional effects such as intrinsic line polarization and occultation effects are required to account for the complex variations seen predominantly in the blue-shifted portion of the lines.