A Near-Infrared and Optical Study of NGC 5822: An Open Cluster Hosting Barium-stars and Lithium-Enriched Giant Stars

Abstract

We present a chemical abundance study of giant stars in the Galactic open cluster NGC 5822, which hosts two barium stars (#002 and #201) and three lithium-enriched giants (#006, #102, and #240). Using high-resolution optical and near-infrared ($H$ and $K$ band) spectra from FEROS and IGRINS, we determine atmospheric parameters and abundances for 23 elements (Li, C, N, O, F, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, Cr, Fe, Ni, Y, Ce, Nd, Yb, and Pb). This includes species not yet studied in this cluster, such as F, P, K, Yb, and Pb, as well as oxygen isotopic ratios ${}^{16}$O/${}^{17}$O and ${}^{16}$O/${}^{18}$O. Membership was assessed using astrometry and chemical abundances, providing insight into the evolutionary stages of Li-enriched giants and cluster parameters (age, distance, extinction). However, the identification of Ba-stars remains challenging due to their binary nature and less reliable astrometric solutions. The cluster's abundances are broadly consistent with expectations for the Galactic thin disk. The mean fluorine abundance agrees with chemical evolution models predicting that young clusters (<2 Gyr) exhibit elevated [F/Fe], with production from SN II, SN Ia, AGB, and Wolf-Rayet stars. No distinct chemical or rotational features were found to explain the lithium enrichment, likely occurring either during the red clump phase or near the RGB tip. For the Ba-stars, nucleosynthesis models combined with the cluster's turn-off mass suggest polluting companion masses of 3.00 and 3.75 $M_{\odot }$ for stars #002 and #201. These results highlight the importance of open clusters as laboratories for chemically peculiar stars.

18 pages, 11 figures, 8 tables, accepted for publication in MNRAS

References in corpus (50)

• Gaia Data Release 3: Summary of the content and survey properties
• Gaia Early Data Release 3: The astrometric solution
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Painting a portrait of the Galactic disc with its stellar clusters
• Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
• Updated parameters of 1743 open clusters based on Gaia DR2
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Age determination for 269 $Gaia$ DR2 Open Clusters
• ARES v2 - new features and improved performance
• Mixed modes in red giants: a window on stellar evolution
• The Gaia-ESO Public Spectroscopic Survey: Implementation, data products, open cluster survey, science, and legacy
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• Evolution and nucleosynthesis of asymptotic giant branch stellar models of low metallicity
• The Open Cluster Chemical Abundances and Mapping Survey: IV. Abundances for 128 Open Clusters using SDSS/APOGEE DR16
• Elemental abundances in the atmosphere of clump giants
• Non-LTE aluminium abundances in late-type stars
• The origin and evolution of the odd-Z iron-peak elements Sc, V, Mn, and Co in the Milky Way stellar disk
• ASteCA - Automated Stellar Cluster Analysis
• Mg line formation in late-type stellar atmospheres: I. The model atom
• linemake: An Atomic and Molecular Line List Generator
• Gaia EDR3 Reveals the Substructure and Complicated Star Formation History of the Greater Taurus-Auriga Star Forming Complex
• The Open Cluster Chemical Abundances and Mapping Survey: VI. Galactic Chemical Gradient Analysis from APOGEE DR17
• The s Process and Beyond
• pyUPMASK: an improved unsupervised clustering algorithm
• Most Lithium-rich Low-mass Evolved Stars Revealed as Red Clump stars by Asteroseismology and Spectroscopy
• The Gaia-ESO survey: Mixing processes in low-mass stars traced by lithium abundance in cluster and field stars
• The GALAH survey: A census of lithium-rich giant stars
• A helium-flash-induced mixing event can explain the lithium abundances of red clump stars
• The Gaia-ESO Survey: Age-chemical-clock relations spatially resolved in the Galactic disc
• Population synthesis of helium white dwarf--red giant star mergers and the formation of lithium-rich giants and carbon stars
• The mass-ratio and eccentricity distributions of barium and S stars, and red giants in open clusters
• The Chemical Evolution of Fluorine in the Bulge - High-resolution K-band spectra of giants in three fields
• A new solar fluorine abundance and a fluorine determination in the two open clusters M 67 and NGC 6404
• Barium stars as tracers of s-process nucleosynthesis in AGB stars I. 28 stars with independently derived AGB mass
• Oxygen isotopic ratios in intermediate-mass red giants
• Exploring the s-process history in the Galactic disk: Cerium abundances and gradients in Open Clusters from the OCCAM/APOGEE sample
• Fluorine in the solar neighbourhood: the need for several cosmic sources
• The Galactic Chemical Evolution of phosphorus observed with IGRINS
• Three open clusters containing Cepheids: NGC 6649, NGC 6664 and Berkeley 55
• On the observational characteristics of lithium-enhanced giant stars in comparison with normal red giants
• The Active Chromospheres of Lithium-Rich Red Giant Stars
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. II. NGC 752
• Chemical Evolution of Ytterbium in the Galactic Disk
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940
• M Giants with IGRINS II. Chemical Evolution of Fluorine at High Metallicities
• Evidence of Deep Mixing in IRS 7, a Cool Massive Supergiant Member of the Galactic Nuclear Star Cluster
• Li-rich giant stars under scrutiny: Binarity, magnetic activity and the evolutionary status after Gaia DR2
• On the validity of the spectroscopic age indicators [Y/Mg], [Y/Al], [Y/Si], [Y/Ca], and [Y/Ti] for giant stars
• The enigma of Li-rich giants and its relation with temporal variations observed in radial velocity and stellar activity signals
• Exploring fluorine chemical evolution in the Galactic disk: the open cluster perspective