On the significance of population II Li6 abundances

Abstract

We explore possible depletion factors for Li6 in the three stars where it has been detected. To this end, we assume that 6Li/H scales as 16O/H throughout the galactic evolution, an assumption motivated by the observations of a similar scaling for 9Be. We examine the uncertainties attached to this modeling of 6Li galactic evolution; we also incorporate a recent evaluation of the primordial production of 6Li. The depletion factor D6, for 6Li, in HD84937, is constrained to be less than 4 at 95% c.l.. This depletion factor is an extreme upper limit on the depletion factor for 7Li. We conclude that the primordial abundance of 7Li cannot be higher that twice the observed value, since no current stellar model is able to reproduce the observed trends of 7Li with temperature and metallicity, and yet deplete 7Li by more than a factor 2, while satisfying D6<4. All three 6Li observations are in excellent agreement with all standard expectations: Big-Bang nucleosynthesis with 2<${\eta }_{10}$<6.5, and standard isochrones of 6Li survival. We discuss possible deviations from our assumption of 6Li/H scaling with 16O/H, due to alpha-alpha creation of 6Li in various sites. We notably reject stellar flares as a significant source of 6Li in HD84937.

19 pages, 4 figures, LaTeX. To appear in ApJ

Cited by in corpus (23)

• Big-Bang Nucleosynthesis and Hadronic Decay of Long-Lived Massive Particles
• Big-bang Nucleosynthesis Enters the Precision Era
• Did Something Decay, Evaporate, or Annihilate during Big Bang Nucleosynthesis?
• Big-Bang Nucleosynthesis with Unstable Gravitino and Upper Bound on the Reheating Temperature
• Review of Big Bang Nucleosynthesis and Primordial Abundances
• Halo Star Lithium Depletion
• Light Elements and Cosmic Rays in the Early Galaxy
• The Lithium Content of the Galactic Halo Stars
• Big Bang Nucleosynthesis with Long Lived Charged Massive Particles
• Radiative decay of a massive particle and the non-thermal process in primordial nucleosynthesis
• The Evolution of Li6 in Standard Cosmic-Ray Nucleosynthesis
• Lithium-6 : Evolution from Big Bang to Present
• Lithium-Beryllium-Boron : Origin and Evolution
• Nuclear Reaction Rates and Primordial ${}^6$Li
• Inhomogeneous Big Bang Nucleosynthesis: Upper Limit on Omega_b and Production of Lithium, Beryllium, and Boron
• Generalized Limits to the Number of Light Particle Degrees of Freedom from Big Bang Nucleosynthesis
• Is 6-Li in metal-poor halo stars produced in situ by solar-like flares?
• A Stochastic Approach to Chemical Evolution
• Cosmic Lithium-Beryllium-Boron Story
• Big Bang Nucleosynthesis
• Big Bang Nucleosynthesis
• 6^Li in the atmosphere of GJ 117
• Big Bang Nucleosynthesis and Related Observations