Lithium abundances of halo dwarfs based on excitation temperature. I. LTE

Abstract

The discovery of the Spite plateau in the abundances of 7Li for metal-poor stars led to the determination of an observationally deduced primordial lithium abundance. However, after the success of the Wilkinson Microwave Anisotropy Probe (WMAP) in determining the baryon density, OmegaBh^2, there was a discrepancy between observationally determined and theoretically determined abundances in the case of 7Li. One of the most important uncertain factors in the calculation of the stellar 7Li abundance is the effective temperature, Teff. We use sixteen metal-poor halo dwarfs to calculate new Teff values using the excitation energy method. With this temperature scale we then calculate new Li abundances for this group of stars in an attempt to resolve the 7Li discrepancy. Using high signal-to-noise (S/N ~ 100) spectra of 16 metal-poor halo dwarfs, obtained with the UCLES spectrograph on the AAT, measurements of equivalent widths from a set of unblended FeI lines are made. These equivalent widths are then used to calculate new Teff values with the use of the single line radiative transfer program WIDTH6, where we have constrained the gravity using either theoretical isochrones or the Hipparcos parallax, rather than the ionization balance. The lithium abundances of the stars are calculated with these temperatures. The physical parameters are derived for the 16 programme stars, and two standards. These include Teff, log g, [Fe/H], microturbulence and 7Li abundances. A comparison between the temperature scale of this work and those adopted by others has been undertaken. We find good consistency with the temperatures derived from the Halpha line by Asplund et al. (2006), but not with the hotter scale of Melendez & Ramirez (2004).

13 pages, 9 figures

References in corpus (8)

• A probable stellar solution to the cosmological lithium discrepancy
• First stars VII. Lithium in extremely metal poor dwarfs
• Coupled Variations of Fundamental Couplings and Primordial Nucleosynthesis
• Bound-State Effects on Light-Element Abundances in Gravitino Dark Matter Scenarios
• Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination
• Stau-catalyzed ${}^6$Li Production in Big-Bang Nucleosynthesis
• From First Stars to the Spite Plateau: a Possible Reconciliation of Halo Stars Observations with Predictions from Big Bang Nucleosynthesis
• Non-LTE Balmer line formation in late-type spectra: Effects of atomic processes involving hydrogen atoms

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• 6Li/7Li estimates for metal-poor stars
• Lithium and Beryllium in the Gaia-Enceladus Galaxy
• The cosmological Lithium problem outside the Galaxy: the Sagittarius globular cluster M54
• Detailed Iron-Peak Element Abundances in Three Very Metal-Poor Stars
• The Axial Rotation and Variable Macroturbulence of RR Lyrae and Red Horizontal Branch Stars
• 12C/13C ratio and CNO abundances in the classical very old metal-poor dwarf HD 140283
• Gravitino dark matter and the lithium primordial abundance within a pre-BBN modified expansion