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On a Rapid Lithium Enrichment and Depletion of K Giant Stars
A model scenario has recently been introduced by de la Reza andcolleagues to explain the presence of very strong Li lines in thespectra of some low-mass K giant stars. In this scenario all ordinary,Li-poor, K giants become Li rich during a short time (~105 yr) whencompared to the red giant phase of 5 x 107 yr. In this "Li period," alarge number of the stars are associated with an expanding thincircumstellar shell supposedly triggered by an abrupt internal mixingmechanism resulting in a surface new 7Li enrichment. This Letterpresents nearly 40 Li-rich K giants known up to now. The distribution ofthese Li-rich giants, along with 41 other observed K giants that haveshells but are not Li rich, in a color-color IRAS diagram confirms thisscenario, which indicates, also as a new result, that a rapid Lidepletion takes place on a timescale of between ~103 and 105 yr. Thismodel explains the problem of the presence of K giants with far-infraredexcesses presented by Zuckerman and colleagues. Other present and futuretests of this scenario are briefly discussed.
| Luminosity Class III Stars with Excess Far-Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...446L..79Z&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Telescopio |
| Ascensione retta: | 19h07m03.16s |
| Declinazione: | -51°55'53.5" |
| Magnitudine apparente: | 8.822 |
| Distanza: | 222.222 parsec |
| Moto proprio RA: | 1.4 |
| Moto proprio Dec: | -6.2 |
| B-T magnitude: | 10.537 |
| V-T magnitude: | 8.964 |
Cataloghi e designazioni:
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