Be abundances in cool main-sequence stars with exoplanets

TL;DR

This study measures beryllium abundances in cool main-sequence stars with and without exoplanets, revealing significant Be depletion in cooler stars that current models cannot explain, regardless of planetary presence.

Contribution

It provides the first extensive analysis of Be abundances across a wide temperature range in stars with and without planets, highlighting unexplained Be depletion mechanisms in cool stars.

Findings

Be depletion increases significantly below 5500 K.

Be abundances are roughly constant in hotter stars.

No clear Be difference between stars with and without planets.

Abstract

We present new UVES spectra of a sample of 15 cool unevolved stars with and without detected planetary companions. Together with previous determinations, we study Be depletion and possible differences in Be abundances between both groups of stars. We obtain a final sample of 89 and 40 stars with and without planets, respectively, which covers a wide range of effective temperatures, from 4700 K to 6400 K, and includes several cool dwarf stars for the first time. We determine Be abundances for these stars and find that for most of them (the coolest ones) the BeII resonance lines are often undetectable, implying significant Be depletion. While for hot stars Be abundances are aproximately constant, with a slight fall as Teff decreases and the Li-Be gap around 6300 K, we find a steep drop of Be content as Teff decreases for Teff < 5500 K, confirming the results of previous papers. Therefore, for these stars there is an unknown mechanism destroying Be that is not reflected in current models of Be depletion. Moreover, this strong Be depletion in cool objects takes place for all the stars regardless of the presence of planets, thus, the effect of extra Li depletion in solar-type stars with planets when compared with stars without detected planets does not seem to be present for Be, although the number of stars at those temperatures is still small to reach a final conclusion.