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Lithium in late-type giants. III - The weak G band giants
Li abundances are presented for nine different stars to demonstrate thatthe abundances are consistent with the cosmic value. The observationswere made with the coude telescope and echelle spectrometer on La Silla,covering the Li I 6707 A resonance doublet and the 800 A 2-0 band. Thesurvey included the HD stars 18636, 31274, 36552, 40402, 78146 and 82595and the HR stars 1299 and 4154, all Southern Hemisphere weak FraunhoferG band objects. Both Li-6 and Li-7 were detected in HR 1299. It issuggested that the Li detected in all the stars convected outwardquickly and survived, while C diffused inward and was converted to C-13and N-14. The Li abundances can be observed in both main sequence andred giant stars.
| The lithium in weak G-band stars
Available data on Li abundance and CH band weakness in weak G-band starsindicates the existence of a linear relationship between Li and carbonabundance. Weak G-band stars with a high Li abundance are least depletedin C, and weak G-band stars with a relatively low Li abundance have avery low abundance of C. Li production seems to be a necessity after thestar leaves the main sequence and reaches the giant branch, probably byspallation reactions on the surface. Then mixing due to meridionalcirculation on the giant branch might bring out the CN-processedmaterial to the surface, at the same time destroying the surface Li.Thus, both C and Li abundances are depleted together.
| The lithium abundance in weak-G band stars
Lithium abundances are derived for ten weak-G band giants. The stars arefound to have at least normal lithium abundances, and may have enhancedlithium relative to normal giants of similar temperature. Also, broadlines found in the G5 giant HR 1023 can be interpreted as rotation witha variable radial velocity of amplitude 17 + or - 5 km/sec. Possibleinterpretations of these results are discussed.
| Observations of weak G-band stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978MNRAS.185..585R&db_key=AST
| HD 91805 and the nature of the Bidelman-MacConnell weak-G-band stars
Spectroscopic and photometric observations of the weak-G-band star HD91805 are examined together with intermediate-band photometry of severalBidelman-MacConnell objects. Curve-of-growth and spectrum-synthesisanalyses of HD 91805 are performed to obtain insight into the productsof mixing; the results are found to be very similar to those reported bySneden and Peterson (1977) for HR 6766. Evidence based on theintermediate-band photometry is presented that the majority of theBidelman-MacConnell weak-G-band stars are burning helium in their coressubsequent to the helium core flash. Possible causes of the weak-G-bandanomaly are considered, and it is concluded that carbon depletion due tomeridional circulation requires the least radical departure from nowwell-understood astrophysical processes.
| The strength of the 2.3 MU CO band in weak-G-band stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..660H&db_key=AST
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