Fundamental parameters of massive stars in multiple systems: The cases of HD17505A and HD206267A

TL;DR

This study investigates the fundamental parameters of massive stars in binary systems HD17505A and HD206267A, revealing their orbital characteristics, stellar properties, and signs of past or ongoing binary interactions using spectral analysis.

Contribution

The paper provides detailed analysis of the orbital and stellar parameters of two massive binary systems, including spectral disentangling and CNO abundance measurements, highlighting their evolutionary states and interaction history.

Findings

HD17505Aa components are inside their Roche lobes, indicating no current binary interaction.

HD206267Aa primary nearly fills its Roche lobe at periastron, suggesting possible past binary interaction.

CNO abundances show slight modifications, consistent with evolutionary models.

Abstract

Many massive stars are part of binary or higher multiplicity systems. The present work focusses on two higher multiplicity systems: HD17505A and HD206267A. Determining the fundamental parameters of the components of the inner binary of these systems is mandatory to quantify the impact of binary or triple interactions on their evolution. We analysed high-resolution optical spectra to determine new orbital solutions of the inner binary systems. After subtracting the spectrum of the tertiary component, a spectral disentangling code was applied to reconstruct the individual spectra of the primary and secondary. We then analysed these spectra with the non-LTE model atmosphere code CMFGEN to establish the stellar parameters and the CNO abundances of these stars. The inner binaries of these systems have eccentric orbits with e ~ 0.13 despite their relatively short orbital periods of 8.6 and 3.7 days for HD17505Aa and HD206267Aa, respectively. Slight modifications of the CNO abundances are found in both components of each system. The components of HD17505Aa are both well inside their Roche lobe, whilst the primary of HD206267Aa nearly fills its Roche lobe around periastron passage. Whilst the rotation of the primary of HD206267Aa is in pseudo-synchronization with the orbital motion, the secondary displays a rotation rate that is higher. The CNO abundances and properties of HD17505Aa can be explained by single star evolutionary models accounting for the effects of rotation, suggesting that this system has not yet experienced binary interaction. The properties of HD206267Aa suggest that some intermittent binary interaction might have taken place during periastron passages, but is apparently not operating anymore.