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14C in AGB stars: the case of IRC+10216
M. Forestini 1,
M. Guélin 2 and
J. Cernicharo 3
Received 21 February 1996 / Accepted 31 May 1996
Observations and stellar evolution computations have been dedicated to the search for in the archetype of AGB stars, IRC+10216/CW Leo. Contrary to Wright's (1994) tentative detection, we see no trace of in this star down to a limit / . The new limit is consistent with our stellar evolution computations, which indicate that R should be . Comparison of the C, N, O, Mg, Si, and S isotopic ratios observed in this source with the calculated ones reinforces our earlier conclusion that CW Leo had a main sequence mass (see Guélin et al. 1995).
While searching for the 2-1 line, we detected the (1 ) line of vibrationally excited SiC2. The latter line pertains to the first vibrational level of the bending state and its upper level has an energy of 290 K, lower than the temperature of the dust forming shell. The line has a pyramidal shape and shows acceleration steps, which we interpreted in terms of dust formation.
Key words: stars: AGB stars: IRC +10216 nucleosynthesis stars: abundances molecular data radio lines: stars
Send offprint requests to: M. Forestini
Online publication: July 8, 1998