Metallicity dependence of carbon-star wind expansion

Determine whether the winds of carbon-rich asymptotic giant branch stars are slowed at lower metallicity despite their production of refractory carbonaceous material through helium-shell-burning dredge-up.

Background

The paper discusses whether the wind-expansion velocities of asymptotic giant branch stars depend on environmental metallicity. Evidence from oxygen-rich stars and earlier observations suggests that lower metallicity may produce slower winds because of a reduced abundance of refractory dust-forming material.

Carbon stars complicate this interpretation because they synthesize and dredge up carbon during helium-shell burning, potentially making their supply of refractory material less dependent on the initial metallicity. The authors therefore identify it as unresolved whether carbon-star winds experience the same metallicity-related slowing. The paper's observations compare carbon stars in the Magellanic Clouds with Galactic samples to investigate related trends, but the quoted uncertainty remains explicitly unresolved in the stated passage.

References

However, since carbon stars produce their own refractory material through the dredge-up of carbon produced during helium shell burning and thus therefore largely independent of the initial metallicity it has been unclear whether their winds are similarly slowed.

— CO rotational line emission in very red carbon stars in the Magellanic Clouds  (2608.16456 - Groenewegen et al., 17 Aug 2026) in Section 1, Introduction