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Carbon stars with oxygen-rich circumstellar materialThe IUE satellite was used to search for companions to two carbon-rich stars with oxygen-rich circumstellar envelopes, EU And and V778 Cyg. Depending upon the amount of interstellar extinction and distances (probably between 1 and 2 kpc from the Sun) to these two stars, upper limits were placed between approx. 1.5 and 6 solar mass to the mass of any main sequence companions. For the 'near' distance of 1 kpc, it seems unlikely that there are white dwarf companions because the detection would be expected of ultraviolet emission from accretion of red giant wind material onto the white dwarf. A new model is proposed to explain the oxygen-rich envelopes. If these stars have a high nitrogen abundance, the carbon that is in excess of the oxygen may be carried in the circumstellar envelopes in HCN rather than C2H2 which is a likely key seed molecule for the formation of carbon grains. Consequently, carbon particles may not form; instead, oxygen-rich silicate dust may nucleate from the SiO present in the outflow.
Document ID
19920011972
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Jura, Michael (California Univ. Los Angeles, CA, United States)
Hawkins, I. (California Univ. Berkeley., United States)
Date Acquired
September 6, 2013
Publication Date
January 16, 1991
Subject Category
Astrophysics
Report/Patent Number
NASA-CR-190161
NAS 1.26:190161
Accession Number
92N21215
Funding Number(s)
CONTRACT_GRANT: NAG5-1406
CONTRACT_GRANT: NAS5-30180
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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