Farihi, Jay; Sanders, Jason L; Lilleengen, Sophia; Whitehouse, Lewis J; Erkal, Denis; (2025) Carbon-enhanced dwarf stars are predominantly a halo population. Monthly Notices of the Royal Astronomical Society , 543 (1) pp. 851-861. 10.1093/mnras/staf1512.

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Abstract

This paper reports a Galactic kinematical and dynamical analysis of 1003 main-sequence carbon stars. The sample is drawn from the Sloan Digital Sky Survey, and cross-matched with Gaia DR3 to obtain 6-dimensional positions and velocities using a Bayesian framework. The study provides the first reliable distances for a large sample of dwarf carbon stars, which are then analysed using both space motions and actions. The results are combined with dynamical equilibrium models for the three primary Galactic components to assign membership, finding that around 60 per cent belong to the halo, and over 30 per cent originate in the thick disc. Therefore, the results indicate dwarf carbon stars are dominated by a metal-poor halo population, and are thus an excellent resource for stellar archaeology. These stars remain on the main sequence and are relatively nearby, but atmospheric modelling is challenged by their cool effective temperatures and strong molecular features. In light of this, efforts should be made to improve C/O $>1$ atmospheric modelling, as the subset of low-mass dwarf carbon stars may numerically dominate the Galactic population of carbon-enriched, metal-poor stars.

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