Spectroscopic abundance analyses of the 3He stars HD 185330 and 3 Cen A

Abstract

Abstract Abundances of 21 elements in two 3He stars, HD 185330 and 3 Cen A, have been analysed relative to the well-studied sharp-lined B3 V star ι Her. Six elements (P, Ti, Mn, Fe, Ni, and Br) are over-abundant in these two peculiar stars, while six elements (C, O, Mg, Al, S, and Cl) are under-abundant. Absorption lines of the two rarely observed heavy elements Br ii and Kr ii are detected in both stars and these elements are both over-abundant. The centroid wavelengths of the Ca ii infrared triplet lines in these stars are redshifted relative to those lines in ι Her and the presence of heavy isotopes of Ca (mass number 44–46) in these two stars is confirmed. In spite of these similarities, there are several remarkable differences in abundance pattern between these two stars. N is under-abundant in HD 185330, as in many Hg-Mn stars, while it is significantly over-abundant in 3 Cen A. P and Ga are both over-abundant in 3 Cen A, while only P is over-abundant and no trace of absorption line of Ga ii can be found in HD 185330. Large over-abundances of Kr and Xe are found in both stars, while the abundance ratio Kr/Xe is significantly different between them (−1.4 dex in HD 185330 and +1.2 dex in 3 Cen A). Some physical explanations are needed to account for these qualitative differences.