Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 1979
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979apj...233..205b&link_type=abstract
Astrophysical Journal, Part 1, vol. 233, Oct. 1, 1979, p. 205-210.
Astronomy and Astrophysics
Astrophysics
41
Carbon Stars, Chemical Composition, Stellar Spectra, Stellar Structure, Variable Stars, Abundance, Barium, Line Spectra, R Coronae Borealis Stars, Spectral Bands, Stellar Envelopes
Scientific paper
U Aquarii is a cool faint R CrB-type variable star. Its spectrum has been found to show the following remarkable features: no trace of hydrogen absorption lines or CH bands, strong bands of (C-12)2 and CN, and extraordinarily strong lines of Sr II and Y II. U Aquarii is the first hydrogen-deficient carbon star known to show enhanced abundances of s-process elements; but the s-processing was unusual in that it produced Sr and Y abundances of about 100 times normal, but little or no Ba. It is suggested that U Aqr is the helium-carbon core of an evolved star of about 1 solar mass that ejected most of its hydrogen-rich envelope at the helium core flash. The s-process abundances can most easily be understood in terms of a single neutron exposure that occurred at the core flash, characterized by a neutron exposure of about 0.6 per mb.
Bond Howard E.
Luck Earle R.
Newman Michael J.
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