Probing lambda Bootis formation models using multiple systems

ALACORIA, J.; MIQUELARENA, P.; SAFFE, C.

Tucumán

Congreso; IV Jornadas de Astrofísica Estelar; 2022

Our aim is to test the accretion scenario of λ Boötis stars. This model predicts that a binary system with two early-type stars passing through a diffuse cloud should both display the same superficial peculiarity. We carried out a detailed abundance determination of three multiple systems hosting a candidate λ Boö star: the remarkable triple system HD 15164/65/65C and the binary systems HD 193256/281 and HD 198160/161. The abundance analysis of HD 15164/65/65C shows a clear λ Boö object (HD 15165) and two objects with near solar composition (HD 15164 and 15165C). Notably, the presence of a λ Boö star (HD 15165) together with a near solar early-type object (HD 15164) is difficult to explain under the accretion scenario. Also, the solar-like composition derived for the late-type star of the system (HD 15165C) could be used, for the first time, as a proxy for the initial composition of the λ Boötis stars. Then, by reviewing abundance analysis of all known binary systems with candidate λ Boö stars from literature and including the systems analyzed here, we find no binary/multiple system having two clear "bonafide" λ Boö stars, as expected from the accretion scenario. The closer candidates to show two λ Boötis-like stars are HD 84948, HD 171948 and HD 198160; however, in our opinion they show mild rather than clear λ Boö patterns. Our results brings little support to the accretion scenario. Then, there is an urgent need of additional binary and multiple systems to be analyzed through a detailed abundance analysis.