On the discovery of K-enhanced and possibly Mg-depleted stars throughout the Milky Way

Abstract

Stars with unusual elemental abundances offer clues about rare astrophysical events or nucleosynthetic pathways. Stars with significantly depleted magnesium and enhanced potassium ([Mg/Fe] < -0.5; [K/Fe] > 1) have to date only been found in the massive globular cluster NGC 2419 and, to a lesser extent, NGC 2808. The origin of this abundance signature remains unknown, as does the reason for its apparent exclusivity to these two globular clusters. Here we present 112 field stars, identified from 454,180 LAMOST giants, that show significantly enhanced [K/Fe] and possibly depleted [Mg/Fe] abundance ratios. Our sample spans a wide range of metallicities (-1.5 < [Fe/H] < 0.3), yet none show abundance ratios of [K/Fe] or [Mg/Fe] that are as extreme as those observed in NGC 2419. If confirmed, the identified sample of stars represents evidence that the nucleosynthetic process producing the anomalous abundances ratios of [K/Fe] and [Mg/Fe] probably occurs at a wide range of metallicities. This would suggest that pollution scenarios that are limited to early epochs (such as Population III supernovae) are an unlikely explanation, although they cannot be ruled out entirely. This sample is expected to help guide modelling attempts to explain the origin of the Mg-K abundance signature.

References in corpus (20)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• Optimal Techniques in Two-dimensional Spectroscopy: Background Subtraction for the 21st Century
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• The Evolution of Isotope Ratios in the Milky Way Galaxy
• Spectroscopic determination of masses (and implied ages) for red giants
• News from the Galactic suburbia: the chemical composition of the remote globular cluster NGC 2419
• Metallicity and Alpha-Element Abundance Measurement in Red Giant Stars from Medium Resolution Spectra
• The Bizarre Chemical Inventory of NGC 2419, An Extreme Outer Halo Globular Cluster
• Label Transfer from APOGEE to LAMOST: Precise Stellar Parameters for 450,000 LAMOST Giants
• Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
• Potassium: a new actor on the globular cluster chemical evolution stage. The case of NGC 2808
• On Potassium and Other Abundance Anomalies of Red Giants in NGC 2419
• Potassium in globular cluster stars: comparing normal clusters to the peculiar cluster NGC 2419
• The Potassium abundance in the globular clusters NGC104, NGC6752 and NGC6809
• Abundances of Na, Mg, and K in the atmospheres of red giant branch stars of Galactic globular cluster 47 Tucanae
• Novae in Globular Clusters
• A Tale of Tidal Tails in the Milky Way
• TeV cosmic-ray proton and helium spectra in the myriad model II

Cited by in corpus (9)

• The Southern Stellar Stream Spectroscopic Survey (S5): Chemical Abundances of Seven Stellar Streams
• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• The Relationship Between Globular Cluster Mass, Metallicity, and Light Element Abundance Variations
• Abundances in the Milky Way across five nucleosynthetic channels from 4 million LAMOST stars
• Discovery of a new stellar sub-population residing in the (inner) stellar halo of the Milky Way
• Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO) I. An updated census of APOGEE N-rich giants across the Milky Way
• A data-driven model of nucleosynthesis with chemical tagging in a lower-dimensional latent space
• Search for Extremely Metal-Poor Stars with GEMINI-N/GRACES I. Chemical-Abundance Analysis
• The Astrophysical Variance in Gaia-RVS Spectra