Mid-infrared interferometry on spectral lines: III. Ammonia and Silane around IRC+10216 and VY CMa

Abstract

Using the U.C. Berkeley Infrared Spatial Interferometer with an RF filterbank, the first interferometric observations of mid-infrared molecular absorption features of ammonia (NH_3) and silane (SiH_4) with very high spectral resolution (R ~ 100000) were made. Under the assumptions of spherical symmetry and uniform outflow, these new data permitted the molecular stratification around carbon star IRC+10216 and red supergiant VY CMa to be investigated. For IRC+10216, both ammonia and silane were found to form in the dusty outflow significantly beyond both the dust formation and gas acceleration zones. Specifically, ammonia was found to form before silane in a region of decaying gas turbulence (>~ 20 R_star), while the silane is produced in a region of relatively smooth gas flow much further from the star (>~ 80 R_star). The depletion of gas-phase SiS onto grains soon after dust formation may fuel silane-producing reactions on the grain surfaces. For VY CMa, a combination of interferometric and spectral observations suggest that NH_3 is forming near the termination of the gas acceleration phase in a region of high gas turbulence (~ 40 R_star).

31 Pages, Accepted in the Astrophysical Journal

References in corpus (4)

• Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres
• The last gasps of VY CMa: Aperture synthesis and adaptive optics imagery
• Mid-infrared interferometry on spectral lines: II. Continuum (dust) emission around IRC+10216 and VY CMa
• Mid-infrared interferometry on spectral lines: I. Instrumentation

Cited by in corpus (30)

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• Mid-infrared interferometry on spectral lines: II. Continuum (dust) emission around IRC+10216 and VY CMa
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• Modern optical astronomy: technology and impact of interferometry
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• Herschel/HIFI deepens the circumstellar NH3 enigma
• The abundance of 28Si32S, 29Si32S, 28Si34S, and 30Si32S in the inner layers of the envelope of IRC+10216
• Circumstellar ammonia in oxygen-rich evolved stars
• Silicon and hydrogen chemistry under laboratory conditions mimicking the atmosphere of evolved stars
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• The ISO Long Wavelength Spectrometer line spectrum of VY Canis Majoris and other oxygen-rich evolved stars
• Herschel/HIFI observations of the circumstellar ammonia lines in IRC+10216
• The maser emitting structure and time variability of the SiS lines J=14-13 and 15-14 in IRC+10216
• The chemistry of extragalactic carbon stars
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• Laboratory Rotational Spectra of Silyl Isocyanide