Beryllium Abundances of Solar-Analog Stars

TL;DR

This study analyzed beryllium abundances in 118 solar analogs, revealing that Be depletion correlates with slower rotation and challenging the idea that G-type dwarfs retain their original Be composition.

Contribution

It provides the first extensive Be abundance analysis of solar analogs, showing the relationship between Be depletion and stellar rotation, and revises previous assumptions about Be homogeneity.

Findings

Most stars have Be abundances near solar levels within ±0.2 dex.

Four stars are significantly Be-deficient by more than 2 dex.

Be abundance tends to increase with higher rotational velocity.

Abstract

An extensive beryllium abundance analysis was conducted for 118 solar analogs (along with 87 FGK standard stars) by applying the spectrum synthesis technique to the near-UV region comprising the Be II line at 3131.066 A, in an attempt to investigate whether Be suffers any depletion such as the case of Li showing a large diversity. We found that, while most of these Sun-like stars are superficially similar in terms of their A(Be) (Be abundances) around the solar value within ~ +/- 0.2dex, 4 out of 118 samples turned out strikingly Be-deficient (by more than ~2 dex) and these 4 stars belong to the group of lowest v_e sin i (projected rotation velocity). Moreover, even for the other majority showing an apparent similarity in Be, we can recognize a tendency that A(Be) gradually increases with an increase in v_e sin i. These observational facts suggest that any solar analog star (including the Sun) generally suffers some kind of Be depletion during their lives, where the rotational velocity (or the angular momentum) plays an important role in the sense that depletion tends to be enhanced by slower rotation. Hence, our findings require that the occasionally stated view "G-type dwarfs with T_eff ~< 6000 K are essentially homogeneous in Be with their original composition retained" should be revised. Also, our analysis indicates that the difference of ~0.2 dex in A(Be) between the solar photosphere and the meteorite really exists, implying that "UV missing opacity" is irrelevant at least for this Be II line.