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We obtained near-infrared long-baseline interferometry of IRC+10420 with theAMBER instrument of ESO's Very Large Telescope Interferometer (VLTI) in low andhigh spectral resolution (HR) mode to probe the photosphere and the innermostcircumstellar environment of this rapidly evolving yellow hypergiant. In the HRobservations, the visibilities show a noticeable drop across the Brackett gamma(BrG) line on all three baselines, and we found differential phases up to -25degrees in the redshifted part of the BrG line and a non-zero closure phaseclose to the line center. The calibrated visibilities were corrected forAMBER's limited field-of-view to appropriately account for the fluxcontribution of IRC+10420's extended dust shell. We derived FWHM Gaussian sizesof 1.05 +/- 0.07 and 0.98 +/- 0.10 mas for IRC+10420's continuum-emittingregion in the H and K bands, respectively, and the BrG-emitting region can befitted with a geometric ring model with a diameter of 4.18 +0.19/-0.09 mas,which is approximately 4 times the stellar size. The geometric model alsoprovides some evidence that the BrG line-emitting region is elongated towards aposition angle of 36 degrees, well aligned with the symmetry axis of the outerreflection nebula. The HR observations were further analyzed by means ofradiative transfer modeling using CMFGEN and the 2-D Busche & Hillier codes.Our spherical CMFGEN model poorly reproduces the observed line shape,blueshift, and extension, definitively showing that the IRC+10420 outflow isasymmetric. Our 2-D radiative transfer modeling shows that the blueshifted BrGemission and the shape of the visibility across the emission line can beexplained with an asymmetric bipolar outflow with a high density contrast frompole to equator (8-16), where the redshifted light is substantially diminished.

Resolving the asymmetric inner wind region of the yellow hypergiant IRC+10420 with VLTI/AMBER in low and high spectral resolution mode