2024MNRAS.528.1065O -
Mon. Not. R. Astron. Soc., 528, 1065-1080 (2024/February-2)
High-resolution spectroscopic study of extremely metal-poor stars in the Large Magellanic Cloud.
OH W.S., NORDLANDER T., DA COSTA G.S., BESSELL M.S. and MACKEY A.D.
Abstract (from CDS):
We present detailed abundance results based on Ultraviolet and Visual Echelle Spectrograph high-dispersion spectra for seven very and extremely metal-poor stars in the Large Magellanic Cloud (LMC). We confirm that all seven stars, two of which have [Fe/H] ≤ -3.0, are the most metal-poor stars discovered so far in the Magellanic Clouds. The element abundance ratios are generally consistent with Milky Way halo stars of similar [Fe/H] values. We find that two of the more metal-rich stars in our sample are enhanced in r-process elements. This result contrasts with the literature, where all nine metal-poor LMC stars with higher [Fe/H] values than our sample were found to be rich in r-process elements. The absence of r-process enrichment in stars with lower [Fe/H] values is consistent with a minimum delay time-scale of ∼100 Myr for the neutron star binary merger process to generate substantial r-process enhancements in the LMC. We find that the occurrence rate of r-process enhancement (r-I or r-II) in our sample of very and extremely metal-poor stars is statistically indistinguishable from that found in the Milky Way's halo, although including stars from the literature sample hints at a larger r-II frequency the LMC. Overall, our results shed light on the earliest epochs of star formation in the LMC that may be applicable to other galaxies of LMC-like mass.
Abstract Copyright:
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
Journal keyword(s):
stars: abundances - stars: Population II - Magellanic Clouds
Status at CDS
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