Integral-Field Spectroscopy of the Post Red Supergiant IRC +10420: evidence for an axi-symmetric wind

Ben Davies (1,2), René D. Oudmaijer (2), Kailash C. Sahu (3)

1: RIT
2: University of Leeds
3: STScI

We present NAOMI/OASIS adaptive-optics assisted integral-field spectroscopy of the transitional massive hypergiant IRC +10420, an extreme mass-losing star apparently in the process of evolving from a Red Supergiant toward the Wolf-Rayet phase. To investigate the present-day mass-loss geometry of the star, we study the appearance of the line-emission from the inner wind as viewed when reflected off the surrounding nebula. We find that, contrary to previous work, there is strong evidence for wind axi-symmetry, based on the equivalent-width and velocity variations of H$alpha$ and Fe {sc ii} $lambda$6516. We attribute this behaviour to the appearance of the complex line-profiles when viewed from different angles. We also speculate that the Ti {sc ii} emission originates in the outer nebula in a region analogous to the Strontium Filament of $eta$ Carinae, based on the morphology of the line-emission. Finally, we suggest that the present-day axisymmetric wind of IRC~+10420, combined with its continued blueward evolution, is evidence that the star is evolving toward the B[e] supergiant phase.

Reference: To appear in ApJ
Status: Manuscript has been accepted