New Constraints on the Origin of the Short-Term Cyclical Variability of the Wolf-Rayet Star WR 46

TL;DR

This study investigates the short-term variability of Wolf-Rayet star WR 46 using multi-wavelength observations, finding significant ~8-hour scale fluctuations and supporting non-radial pulsations as the likely cause.

Contribution

The paper provides new FUV, UV, and X-ray observations of WR 46, offering evidence that favors non-radial pulsations over other hypotheses for its variability.

Findings

Detected ~8-hour variability in FUV and X-ray data.

Observed correlated fluctuations across UV, FUV, and X-ray light-curves.

Supported non-radial pulsations as the primary cause of variability.

Abstract

The Wolf-Rayet star WR 46 is known to exhibit a very complex variability pattern on relatively short time scales of a few hours. Periodic but intermittent radial velocity shifts of optical lines as well as multiple photometric periods have been found in the past. Non-radial pulsations, rapid rotational modulation or the presence of a putative low-mass companion have been proposed to explain the short-term behaviour. In an effort to unveil its true nature, we observed WR 46 with FUSE (Far Ultraviolet Spectroscopic Explorer) over several short-term variability cycles. We found significant variations on a time scale of ~8 hours in the far-ultraviolet (FUV) continuum, in the blue edge of the absorption trough of the OVI {\lambda}{\lambda}1032, 1038 doublet P Cygni profile and in the SVI {\lambda}{\lambda}933, 944 P Cygni absorption profile. We complemented these observations with X-ray and UV light-curves and an X-ray spectrum from archival XMM-Newton (X-ray Multi-Mirror Mission - Newton Space Telescope) data. The X-ray and UV light-curves show variations on a time scale similar to the variability found in the FUV. We discuss our results in the context of the different scenarios suggested to explain the short-term variability of this object and reiterate that non-radial pulsations is the most likely to occur.