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

V. Hénault-Brunet (1), N. St-Louis (2), S.V. Marchenko (3), A.M.T. Pollock (4), S. Carpano (5), A. Talavera (4)

(1) SUPA, Institute for Astronomy, University of Edinburgh (2) Université de Montréal (3) Science Systems and Applications, Inc. (4) ESAC (5) ESTEC/ESA

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 O VI λλ1032,1038 doublet P Cygni profile and in the S VI λλ933,944 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.

Reference: ApJ, in press
Status: Manuscript has been accepted