RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 10 April 2015, 14:00-14:20; Duffield Lecture Theatre

John Norris

"The Lithium Abundances of the Most Metal-poor Stars"

The abundance of lithium in metal-poor, near-main-sequence stars lies well below the value obtained from Standard Big Bang Nucleosynthesis constrained by the result of the Wilkinson Microwave Anisotropy Probe. Perhaps the most widely held opinion is that this is driven in large part by an incomplete understanding of the physics of the stars. Indeed, over the past decade of so, very different conclusions based of stellar observations have been put forward concerning the nature of the Spite Plateau in the (A(Li), Teff) and (A(Li), [Fe/H]) - planes. For example, the Plateau has been described as: (i) ultrathin but postprimordial (Ryan et al. 1999); broken (Melendez et al 2010); and (iii) undergoing meltdown (Bonifacio et al 2010). We also know that both of the known dwarfs with [Fe/H] < -4.5 have lithium abundances well below the value on the Spite Plateau. I propose to present further Li abundances for extremely metal-poor dwarfs in the range -4.0 < [Fe/H] < -3.0, and to discuss the tensions and curious differences that currently exist among the various observational results, including those of the most Fe-poor star currently known, SM0313-6708 ([Fe/H] < -7.3).