Probing the mass loss history of the yellow hypergiant IRC+10420

Abstract

We have used the sub-millimeter array to image the molecular envelope around IRC+10420. Our observations reveal a large and clumpy expanding envelope around the star. The molecular envelope shows a clear asymmetry in ${}^{12}$CO J=2--1 emission in the South-West direction. The elongation of the envelope is found even more pronounced in the emission of ${}^{13}$CO J=2--1 and SO J${}_{\mathrm{K}}$=6${}_5$--5${}_4$. A small positional velocity gradient across velocity channels is seen in these lines, suggesting the presence of a weak bipolar outflow in the envelope of IRC+10420. In the higher resolution ${}^{12}$CO J=2--1 map, we find that the envelope has two components: (1) an inner shell (shell I) located between radius of about 1"-2"; (2) an outer shell (shell II) located between 3" to 6" in radius. These shells represent two previous mass-loss episodes from IRC+10420. We attempt to derive in self-consistent manner the physical conditions inside the envelope by modelling the dust properties, and the heating and cooling of molecular gas. We estimate a mass loss rate of $\sim$9 10${}^{-4}$ M${}_{\odot }$ yr${}^{-1}$ for shell I and 7 10${}^{-4}$ M${}_{\odot }$ yr${}^{-1}$ for shell II. The gas temperature is found to be unusually high in IRC+10420 in comparison with other oxygen-rich envelopes. The elevated gas temperature is mainly due to higher heating rate, which results from the large luminosity of the central s tar. We also derive an isotopic ratio ${}^{12}$C/${}^{13}$C = 6.

30 pages, 14 figures. Accepted for publication in The Astrophysical Journal

References in corpus (3)

• The molecular envelope around the red supergiant VY CMa
• Integral-Field Spectroscopy of the Post Red Supergiant IRC +10420: evidence for an axi-symmetric wind
• The chemical composition of the circumstellar envelopes around yellow hypergiant stars

Cited by in corpus (14)

• Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles - II. CO line survey of evolved stars: derivation of mass-loss rate formulae
• Dynamics of Dusty Radiation Pressure Driven Shells and Clouds: Fast Outflows from Galaxies, Star Clusters, Massive Stars, and AGN
• Comparative Spectra of Oxygen-Rich vs. Carbon-Rich Circumstellar Shells: VY Canis Majoris and IRC+10216 at 215-285 GHz
• Searching for Cool Dust in the Mid-to-Far Infrared: the Mass Loss Histories of The Hypergiants $\mu$ Cep, VY CMa, IRC+10420, and $\rho$ Cas
• Magnetic Fields in Evolved Stars: Imaging the Polarized Emission of High-Frequency SiO Masers
• Herschel/HIFI deepens the circumstellar NH3 enigma
• 870 um observations of evolved stars with LABOCA
• A lambda 3mm and 1mm line survey toward the yellow hypergiant IRC +10420
• Circumstellar ammonia in oxygen-rich evolved stars
• Resolving the asymmetric inner wind region of the yellow hypergiant IRC+10420 with VLTI/AMBER in low and high spectral resolution mode
• ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907
• Investigating the nature of the Fried Egg nebula: CO mm-line and optical spectroscopy of IRAS 17163-3907
• Dense molecular clumps in the envelope of the yellow hypergiant IRC+10420
• The Red and Yellow Hypergiants