The chemical composition of HIP34407/HIP34426 and other twin-star comoving pairs

TL;DR

This study analyzes the elemental abundances of a twin-star pair, revealing significant differences correlated with condensation temperature, and explores implications for binary star formation.

Contribution

It provides high-precision differential abundance measurements of a twin-star pair and investigates correlations with stellar parameters and separation, offering new insights into binary star formation.

Findings

HIP34407 is more metal-rich than HIP34426.

Abundance differences correlate with condensation temperature.

Weak correlation between abundance difference and star separation.

Abstract

We conducted a high-precision elemental abundance analysis of the twin-star comoving pair HIP34407/HIP34426. With mean error of 0.013 dex in the differential abundances (D[X/H]), a significant difference was found: HIP34407 is more metal-rich than HIP34426. The elemental abundance differences correlate strongly with condensation temperature, with the lowest for the volatile elements like carbon around 0.05+/-0.02 dex, and the highest up to about 0.22+/-0.01 dex for the most refractory elements like aluminum. Dissimilar chemical composition for stars in twin-star comoving pairs are not uncommon, thus we compile previously-published results like ours and look for correlations between abundance differences and stellar parameters, finding no significant trends with average effective temperature, surface gravity, iron abundance, or their differences. Instead, we found a weak correlation between the absolute value of abundance difference and the projected distance between the stars in each pair that appears to be more important for elements which have a low absolute abundance. If confirmed, this correlation could be an important observational constraint for binary star system formation scenarios.