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Origin of the observed orbital period distribution of Ba/CH/CEMP-s binaries

Investigate the physical mechanisms that produce the observed several-hundred-to-several-thousand-day orbital periods in barium (Ba), CH, and CEMP-s binary systems formed via asymptotic giant branch (AGB) mass transfer, and establish why this specific period distribution is observed across these systems.

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Background

In discussing the low incidence of s-process–enriched, carbon-rich stars in globular clusters, the authors note that typical Ba/CH/CEMP-s binaries have periods from hundreds to thousands of days. These systems are thought to form via mass transfer from an AGB companion.

Despite extensive observations, the physical reasons for this characteristic period range remain unsettled, making the formation and orbital evolution of these binaries an outstanding problem linked to binary interaction physics, mass transfer channels, and dynamical environments.

References

Known Ba/CH/CEMP-s stars have periods of several hundred to several thousand days \citep[e.g.][]{hansen16a, jorissen19}, so these are typically not very close binaries, and could be destroyed relatively easily. We note that there are still some open questions as to why they have the periods that we observe \citep[see e.g.][]{abate18}.

— Predicting metallicities and carbon abundances from Gaia XP spectra for (carbon-enhanced) metal-poor stars (2410.11077 - Ardern-Arentsen et al., 14 Oct 2024) in Section 5.2 (Discussion; For globular cluster stars)