2006ApJ...649..965S -
Astrophys. J., 649, 965-972 (2006/October-1)
The distribution of SiO in the circumstellar envelope around IRC +10216.
SCHOIER F.L., FONG D., OLOFSSON H., ZHANG Q. and PATEL N.
Abstract (from CDS):
New interferometric observations of SiO J=5⟶4 circumstellar line emission around the carbon star IRC +10216 using the Submillimeter Array are presented. Complemented by multitransition single-dish observations, including infrared observations of rovibrational transitions, detailed radiative transfer modeling suggests that the fractional abundance of SiO in the inner part of the envelope, between ~3 and 8 stellar radii, is as high as ~1.5x10–6. This is more than an order of magnitude higher than predicted by equilibrium stellar atmosphere chemistry in a carbon-rich environment and indicative of the importance of non-LTE chemical processes. In addition to the compact component, a spatially more extended (re~2.4x1016 cm) low fractional abundance (f0~1.7x10–7) region is required to fit the observations. This suggests that the majority of the SiO molecules are effectively accreted onto dust grains in the inner wind, while the remaining gas-phase molecules are eventually photodissociated at larger distances. Evidence of departure from a smooth wind is found in the observed visibilities, indicative of density variations of a factor 2-5 on an angular scale corresponding to a timescale of about 200 yr. In addition, constraints on the velocity structure of the wind are obtained.
Abstract Copyright:
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Journal keyword(s):
Stars: Circumstellar Matter - Stars: Abundances - Stars: AGB and Post-AGB - Stars: Carbon - Stars: Individual: Alphanumeric: IRC +10216 - Stars: Mass Loss
Simbad objects:
5
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