Tracing a decade of activity towards a yellow hypergiant. The spectral and spatial morphology of IRC+10420 at au scales

Abstract

The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss history and geometry, with the yellow hypergiants being key objects to study those phases of evolution. We present near-IR interferometric observations of the famous yellow hypergiant IRC +10420 and blue spectra taken between 1994-2019. Our 2.2 $\mu$m GRAVITY/VLTI observations attain a spatial resolution of $\sim$5 stellar radii and probe the hot emission in the K-band tracing the gas via Na i double emission and the Br$\gamma$ emission. The observed configurations spatially resolve the 2.2 $\mu$m continuum as well as the Br$\gamma$ and the Na i emission lines. Our geometric modelling demonstrates the presence of a compact neutral zone (Na i) which is slightly larger than the continuum but within an extended Br$\gamma$ emitting region. Our geometric models of the Br$\gamma$ emission confirm an hour-glass geometry of the wind. To explain this peculiar geometry we investigate the presence of a companion at 7-800 au separations and find no signature at the contrast limit of our observations (3.7 mag at 3$\sigma$). We report an evolution of the ejecta over a time span of 7 years, which allows us to constrain the opening angle of the hour-glass geometry at $<$10${}^{\circ }$. Lastly, we present the first blue optical spectra of IRC +10420 since 1994. The multi-epoch data indicate that the spectral type, and thus temperature, of the object has essentially remained constant during the intervening years. This confirms earlier conclusions that following an increase in temperature of 2000 K in less than two decades prior to 1994, the temperature increase has halted. This suggests that this yellow hypergiant has "hit" the White Wall in the HR-diagram preventing it from evolving blue-wards, and will likely undergo a major mass-loss event in the near future.

Accepted for publication in MNRAS; 13 pages, 7 figures, 2 tables

References in corpus (9)

• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• The impact of mass-loss on the evolution and pre-supernova properties of red supergiants
• Exploring the Mass Loss Histories of the Red Supergiants
• Integral-Field Spectroscopy of the Post Red Supergiant IRC +10420: evidence for an axi-symmetric wind
• Spectropolarimetry of the Massive Post-Red Supergiants IRC +10420 and HD 179821
• HD101584: Circumstellar characteristics and evolutionary status
• Red Supergiants, Yellow Hypergiants, and Post-RSG Evolution
• Pulsations, eruptions, and evolution of four yellow hypergiants

Cited by in corpus (2)

• The circumstellar material around the Type IIP SN 2021yja
• First spatially resolved Na I and He I transitions towards an MYSO. Finding new tracers for the gaseous star/disc interface