Anisotropic winds in a Wolf–Rayet binary identify a potential gamma-ray burst progenitor

The massive evolved Wolf–Rayet stars sometimes occur in colliding-wind binary systems in which dust plumes are formed as a result of the collision of stellar winds¹. These structures are known to encode the parameters of the binary orbit and winds^2–4. Here we report observations of a previously undiscovered Wolf–Rayet system, 2XMM J160050.7–514245, with a spectroscopically determined wind speed of ~3,400 km s⁻¹. In the thermal infrared, the system is adorned with a prominent ~12″ spiral dust plume, revealed by proper motion studies to be expanding at only ~570 km s⁻¹. As the dust and gas appear to be coeval, these observations are inconsistent with existing models of the dynamics of such colliding-wind systems^5–7. We propose that this contradiction can be resolved if the system is capable of launching extremely anisotropic winds. Near-critical stellar rotation is known to drive such winds^8,9, suggesting that this Wolf–Rayet system may be a Galactic progenitor system for long-duration gamma-ray bursts.