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Title: Sulfur chemistry in the envelope of VY Canis Majoris: Detailed analysis of SO and SO{sub 2} emission

Detailed radiative transfer modeling has been carried out for SO{sub 2} and SO originating in the envelope of the O-rich supergiant star VY Canis Majoris (VY CMa). A total of 27 transitions of SO{sub 2} and 7 transitions of SO lying in the energy range 3.0-138.2 cm{sup –1} were analyzed using a new non-LTE radiative transfer code that incorporates non-spherical geometries. The spectra were primarily obtained from the Arizona Radio Observatory (ARO) 1 mm spectral survey of VY CMa, conducted with the Submillimeter Telescope; additional lines were measured with the ARO 12 m antenna at 2 and 3 mm. SO{sub 2} and SO were found to arise from five distinct outflows within the envelope, four which are asymmetric with respect to the star. Three flows arise from high-velocity red-shifted material, one from a blue-shifted wind, and the final from a classic 'spherical' expansion. In the spherical component, the peak fractional abundance, relative to H{sub 2}, of both molecules is f ∼ 2.5 × 10{sup –7} at r ∼ 25 R {sub *}, and steadily decreases outward. SO{sub 2} appears to be a 'parent' molecule, formed near the stellar photosphere. In the asymmetric outflows, both SO and SO{sub 2} are moremore » prominent at large stellar radii in dense (10{sup 6}-10{sup 7} cm{sup –3}), clumpy material, achieving their maximum abundance between 200 and 600 R {sub *} with f ∼ 3.0 × 10{sup –8}-1.5 × 10{sup –7}. These results suggest that in the collimated outflows, both species are either produced by shock chemistry or are remnant inner shell material swept up in the high-velocity winds.« less
Authors:
; ;  [1]
  1. Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, AZ 85721 (United States)
Publication Date:
OSTI Identifier:
22342037
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ANTENNAS; ASYMMETRY; EMISSION; EXPANSION; HYDROGEN; LTE; MATTER; MOLECULES; PHOTOSPHERE; RADIANT HEAT TRANSFER; RED SHIFT; SIMULATION; SPECTRA; SPHERICAL CONFIGURATION; SULFUR; SULFUR DIOXIDE; SUPERGIANT STARS; TELESCOPES; VELOCITY