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The primordial abundance of Li-6 and Be-9
Light element (Li-6, Li-7 and Be-9) depletion isochrones for halo starshave been calculated with standard stellar evolution models. Thesemodels include the latest available opacities and are computed throughthe subgiant branch. If Li-6 is not produced in appreciable amounts bystellar flares, then the detection of Li-6 in HD 84937 by Smith,Lambert, and Nissen is compatible with standard stellar evolution andstandard big bang nucleosynthesis only if HD 84937 is a subgiant. Thepresent parallax is consistent with HD 84937 being a subgiant star atthe 2.5 sigma level. The most metal poor star with a measured Be-9abundance is HD 140283, which is a relatively cool subgiant. Standardstellar evolution predicts that Be-9 will have been depleted in thisstar by approx. 0.3 dex (for Teff = 5640 K). Revising theabundance upward changes the oxygen-beryllium relation, suggestingincompatibility with standard cosmic-ray production models, and hence,standard big bang nucleosynthesis. However, an increase in the derivedtemperature of HD 1402283 to 5740 K would result in little depletion ofBe-9 and agreement with standard big bang nucleosynthesis.
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Osservazione e dati astrometrici
| Costellazione: | Orsa Maggiore |
| Ascensione retta: | 12h15m38.15s |
| Declinazione: | +57°36'26.2" |
| Magnitudine apparente: | 8.212 |
| Distanza: | 141.443 parsec |
| Moto proprio RA: | -80.9 |
| Moto proprio Dec: | 11.7 |
| B-T magnitude: | 8.687 |
| V-T magnitude: | 8.252 |
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