HD 210111: a new lambda Bootis type SB system

TL;DR

This paper identifies HD 210111 as a lambda Bootis type spectroscopic binary, providing detailed spectral analysis and modeling to understand its composition, binary nature, and potential for asteroseismology to study diffusion and accretion processes.

Contribution

It presents the first detailed analysis of a lambda Bootis SB system with known IR-excess, combining spectral modeling and binary component investigation.

Findings

HD 210111 consists of two similar stars with specific stellar parameters.

The system is only the third well-studied lambda Bootis SB system.

It is the first lambda Bootis SB system with confirmed IR-excess.

Abstract

The small group of lambda Bootis stars comprises late B to early F-type stars, with moderate to extreme (up to a factor 100) surface underabundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). The main mechanisms responsible for this phenomenon are atmospheric diffusion, meridional mixing and accretion of material from their surroundings. Especially spectroscopic binary (SB) systems with lambda Bootis type components are very important to investigate the evolutionary status and accretion process in more details. For HD 210111, also delta Scuti type pulsation was found which gives the opportunity to use the tools of asteroseismology for further investigations. The latter could result in strict constraints for the amount of diffusion for this star. Together with models for the accretion and its source this provides a unique opportunity to shed more light on these important processes. We present classification and high resolution spectra for HD 210111. A detailed investigation of the most likely combinations of single star components was performed. For this, composite spectra with different stellar astrophysical parameters were calculated and compared to the observations to find the best fitting combination. HD 210111 comprises two equal (within the estimated errors) stars with T(eff)=7400K, logg=3.8dex, [M/H]=-1.0dex and vsini=30km/s. This result is in line with other strict observational facts published so far for this object. It is only the third detailed investigated lambda Bootis type SB system, but the first one with a known IR-excess.