Oxygen and neon abundances of B-type stars in comparison with the Sun

Abstract

To revisit the long-standing problem of a possible inconsistency concerning the oxygen composition in the current Galactic gas and in the solar atmosphere (i.e., the former being appreciably lower by ∼0.3 dex), apparently contradicting the Galactic chemical evolution, we carried out oxygen abundance determinations for 64 mid- through late-B stars by using the OI 6156-8 lines while taking into account the non-LTE effect, and compared them with the solar O abundance established in the same manner. The resulting mean oxygen abundance was (AO) = 8.71 (±0.06), which means that [O/H] (star-Sun differential abundance) is∼-0.1, the difference being less significant than previously thought. Moreover, since the 3D correctionmay further reduce the reference solar oxygen abundance (8.81) by ∼0.1 dex, we conclude that the photospheric O abundances of these B stars are almost the same as that of the Sun. We also determined the non-LTE abundances of neon for sample B stars from Ne I 6143/6163 lines to be (ANe) = 8.02 (±0.09), leading to an Ne-to-O ratio of ∼0.2, consistent with recent studies. This excludes the possibility of a considerably high Ne/O ratio once proposed as a solution to the confronted solar model problem. © 2010. Astronomical Society of Japan.