http://arxiv.org/abs/2209.12224
We construct a sample of 644 carbon-enhanced metal-poor (CEMP) stars with abundance analyses based on moderate- to high-resolution spectroscopic studies. Dynamical parameters for these stars are estimated, based on radial velocities, Bayesian parallax-based distance estimates, and proper motions from Gaia EDR3 and DR3, supplemented by additional available information where needed. We apply the HDBSCAN clustering method to the specific energies and actions (E, Jr , J{\phi}, Jz ), obtaining 39 individual Chemo-Dynamically Tagged Groups (CDTGs) of CEMP stars. The stars in the full sample of CDTGs exhibit large and statistically insignificant dispersions in [Fe/H], [C/Fe]c, and [Mg/Fe], when compared to random draws from their parent sample. When the clustering is performed on CEMP stars separated into the morphological groups in the Yoon-Beers Diagram, the Group I (primarily CEMP-s and CEMP-r/s) stars exhibit lower (but still statistically insignificant) dispersions in [Fe/H], and larger (statistically insignificant) dispersions in [C/Fe]c and [Mg/Fe]. In contrast, the Group II (primarily CEMP-no) stars exhibit clear similarities, with very low, highly statistically significant, dispersions in [Fe/H] and [C/Fe]c. These results strongly indicate that Group I CEMP stars received their carbon enhancements from local phenomena, such as mass transfer from a evolved binary companion in regions with extended star-formation histories, while the CDTGs of Group II CEMP stars formed in low-metallicity environments that had already been enriched in carbon, likely from massive rapidly rotating ultra and hyper metal-poor stars and/or supernovae associated with high-mass early generation stars.
J. Zepeda, T. Beers, V. Placco, et. al.
Tue, 27 Sep 22
12/89
Comments: Submitted to AAS Journals
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