Non-Gaussian error distribution of 7Li abundance measurements

Abstract

We construct the error distribution of [Formula: see text] abundance measurements for 66 observations (with error bars) used by Spite et al. (2012) that give [Formula: see text] (median and [Formula: see text] symmetrized error). This error distribution is somewhat non-Gaussian, with larger probability in the tails than is predicted by a Gaussian distribution. The 95.4% confidence limits are [Formula: see text] in terms of the quoted errors. We fit the data to four commonly used distributions: Gaussian, Cauchy, Student’s t and double exponential with the center of the distribution found with both weighted mean and median statistics. It is reasonably well described by a widened [Formula: see text] Student’s t distribution. Assuming Gaussianity, the observed A(Li) is [Formula: see text] away from that expected from standard Big Bang Nucleosynthesis (BBN) given the Planck observations. Accounting for the non-Gaussianity of the observed A(Li) error distribution reduces the discrepancy to [Formula: see text], which is still significant.