Beryllium Abundances in Stars of One-Solar-Mass

TL;DR

This study measures beryllium abundances in 50 stars of similar mass to understand their variation with age, temperature, and metallicity, revealing a significant spread and correlation with lithium, and extending Galactic chemical evolution trends.

Contribution

It provides the first detailed analysis of Be abundances in a narrow mass range of stars, showing a large abundance spread and confirming the Be-Fe trend across different Galactic populations.

Findings

Be abundance varies by a factor of over 40 among similar stars.

No dependence of [Be/Fe] on temperature, but a spread of a factor of 6 at fixed temperature.

Be and Fe increase similarly over Galactic time, extending known trends.

Abstract

We have determined Be abundances in 50 F and G dwarfs in the mass range of 0.9 $\leq$ M$_\odot$ $\leq$ 1.1 as determined by Lambert & Reddy. The effective temperatures are 5600 to 6400 K and metallicities from $-$0.65 to +0.11. The spectra were taken primarily with Keck I + HIRES. The Be abundances were found via spectral synthesis of Be II lines near 3130 \AA. The Be abundances were investigated as a function of age, temperature, metallicity and Li abundance in this narrow mass range. Even though our stars are similar in mass, they show a range in Be abundances of a factor of $>$40. We find that [Be/Fe] has no dependence on temperature, but does show a spread of a factor of 6 at a given temperature. The reality of the spread is shown by two identical stars which differ from each other by a factor of two only in their abundances of Li and Be. Our thin-disk-star sample fits the trend between Be abundance and [Fe/H] found for halo and thick disk stars, extending it to about 4 orders of magnitude in the two logarithmic quantities. Both Fe and Be appear to increase similarly over time in the Galaxy. One-third of our sample may be classified as subgiants; these more-evolved stars have lower Be abundances than the dwarfs. They have undergone Be depletion by slow mixing on the main sequence and Be dilution during their trip toward the red giant base. There are both Li and Be detections in 60 field stars in the "Li-plateau" of 5900 - 6300 K now and the abundances of the two light elements are correlated with a slope of 0.34 $\pm$0.05, with greater Li depletion than Be depletion.