THE ORIGIN OF COPPER IN COSMOS

Abstract

Copper appears to be the most problematic element in the context of the Galactic chemodynamics. The dependence of the relative-to-iron copper abundance [Cu/Fe] as a function of the metallicity remains a subject of debate. At very low metallicity, the observed copper abundace is also quite low. Several sources of the copper nuclei production have been proposed. Unfortunately, none of them provides an adequate explanation of such a low abundance. It is discussed here that this problem may be related to the LTE assumption used in spectroscopic studies of copper lines. Andrievsky et al. (2018) and Korotin et al. (2018) have shown that copper lines are strongly influenced by NLTE effects. Overionization of the copper neutral atoms leads to a decrease in the overall absorption in Cu I spectral lines, and as a result, LTE analysis yields a copper underabundance (i.e., NLTE corrections are positive). Correct determination of the copper abundance using the NLTE approximation eliminates this problem. Thus, in the lowmetallicity regime, copper does not exhibit a significant deficiency and behaves essentially as a primary chemical element. Its cosmic production in the earliest stages of the Galaxy evolution may be associated with explosions of massive stars, such as type II supernovae (core-collapse supernovae) and hypernovae. The main source in this case may be the α-rich freeze-out process during the explosive silicon burning.