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dc.contributor.authorOsorio, Yeisson
dc.contributor.authorAguado, David S
dc.contributor.authorPrieto, Carlos Allende
dc.contributor.authorHubeny, Ivan
dc.contributor.authorGonzález Hernández, Jonay I
dc.date.accessioned2022-04-08T12:00:11Z
dc.date.available2022-04-08T12:00:11Z
dc.date.issued2022-04-01
dc.date.submitted2021-12-21
dc.identifier.issn0004-637X
dc.identifier.otherapjac5a53
dc.identifier.otherac5a53
dc.identifier.otheraas36760
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/335910
dc.description.abstract<jats:title>Abstract</jats:title> <jats:p>The Ca <jats:sc>ii</jats:sc> H and K lines are among the few features available to infer the metallicity of extremely metal-poor stars from medium-resolution spectroscopy. Unfortunately, these lines can overlap with absorption produced in the intervening interstellar medium, introducing systematic errors in the derived metallicities. The strength of the Ca <jats:sc>ii</jats:sc> infrared triplet lines can also be measured at extremely low metallicities, and it is not affected by interstellar absorption, but it suffers significant departures from local thermodynamic equilibrium (LTE). We investigate the feasibility of adopting the Ca <jats:sc>ii</jats:sc> infrared triplet as a metallicity indicator in extremely metal-poor stars using state-of-the art non-LTE models including the most recent atomic data. We find that the triplet lines exhibit non-LTE abundance corrections that can exceed 0.5 dex. When interstellar absorption affecting the Ca <jats:sc>ii</jats:sc> resonance lines is accounted for using high-resolution observations, the agreement between non-LTE abundances for the triplet and those for the resonance lines, with only minor departures from LTE, is excellent. Non-LTE effects strengthen the Ca <jats:sc>ii</jats:sc> IR triplet lines, facilitating measurements at very low metallicities, compared with LTE estimates, down to [Fe/H] = −6.0. This result has important implications for the discovery of primitive stars in our Galaxy and others, since instruments are most sensitive at red/near-infrared wavelengths, and tens of millions of spectra covering the Ca <jats:sc>ii</jats:sc> IR triplet will soon become available from the Gaia, DESI, WEAVE, and PFS missions.</jats:p>
dc.languageen
dc.publisherAmerican Astronomical Society
dc.subject340
dc.subjectStars and Stellar Physics
dc.titleAccurate Metallicities for Very Metal-poor Stars from the Ca ii Infrared Triplet
dc.typeArticle
dc.date.updated2022-04-08T12:00:11Z
prism.issueIdentifier2
prism.publicationNameThe Astrophysical Journal
prism.volume928
dc.identifier.doi10.17863/CAM.83344
dcterms.dateAccepted2022-03-01
rioxxterms.versionofrecord10.3847/1538-4357/ac5a53
rioxxterms.versionVoR
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0/
dc.contributor.orcidOsorio, Yeisson [0000-0001-5832-6933]
dc.contributor.orcidAguado, David S [0000-0001-5200-3973]
dc.contributor.orcidPrieto, Carlos Allende [0000-0002-0084-572X]
dc.contributor.orcidHubeny, Ivan [0000-0001-8816-236X]
dc.contributor.orcidGonzález Hernández, Jonay I [0000-0002-0264-7356]
dc.identifier.eissn1538-4357
cam.issuedOnline2022-04-07


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