Abundances of lithium, sodium, and potassium in Vega

TL;DR

This study precisely measured the photospheric abundances of lithium, sodium, and potassium in Vega, revealing mild underabundances likely linked to interstellar gas accretion, with implications for understanding Vega's chemical peculiarities.

Contribution

It provides accurate abundance measurements of Li, Na, and K in Vega using high-quality spectra and accounts for non-LTE and gravity-darkening effects, suggesting a link to interstellar accretion.

Findings

Li is more deficient than Na and K in Vega.

Vega's alkali element abundances are mildly underabundant compared to the Sun.

The abundance pattern suggests interstellar gas accretion influences Vega's composition.

Abstract

Vega's photospheric abundances of Li, Na, and K were determined by using considerably weak lines measured on the very high-S/N spectrum, while the non-LTE correction and the gravity-darkening correction were adequately taken into account. It was confirmed that these alkali elements are mildly underabundant ([Li/H] ~ -0.6, [Na/H] ~ -0.3, and [K/H] ~ -0.2) compared to the solar system values, as generally seen also in other metals. Since the tendency of Li being more deficient than Na and K is qualitatively similar to what is seen in typical interstellar cloud, the process of interstellar gas accretion may be related with the abundance anomaly of Vega, as suspected in the case of lambda Boo stars.