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

TL;DR

This study compares the elemental abundances in two 3He stars, revealing over- and under-abundances of various elements, including rare heavy elements, and highlighting differences in their abundance patterns.

Contribution

It provides detailed spectroscopic abundance analyses of two 3He stars, including rare heavy elements and isotopic compositions, revealing significant differences in their chemical patterns.

Findings

Over-abundance of P, Ti, Mn, Fe, Ni, Br in both stars

Detection of heavy elements Br II and Kr II with over-abundance

Distinct abundance pattern differences between the two stars

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 iota 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 red-shifted relative to those lines in iota Her and the presence of heavy isotopes of Ca (mass number 44 - 46) in these two stars are confirmed. In spite of these similarities, there are several remarkable differences in the 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 ratios Kr / Xe are 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.