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dc.contributor.authorCarlos, Marilia
dc.contributor.authorKarakas, Amanda I.
dc.contributor.authorCohen, Judith G.
dc.contributor.authorKobayashi, Chiaki
dc.contributor.authorMelendez, Jorge
dc.date.accessioned2018-07-03T16:24:34Z
dc.date.available2018-07-03T16:24:34Z
dc.date.issued2018-04-04
dc.identifier.citationCarlos , M , Karakas , A I , Cohen , J G , Kobayashi , C & Melendez , J 2018 , ' A formation timescale of the Galactic halo from Mg isotopes in dwarf stars ' , The Astrophysical Journal , vol. 856 , no. 2 , 161 . https://doi.org/10.3847/1538-4357/aab36c
dc.identifier.issn0004-637X
dc.identifier.otherPURE: 14856399
dc.identifier.otherPURE UUID: a58dcc6c-0d86-46df-8000-9b3532061a64
dc.identifier.otherArXiv: http://arxiv.org/abs/1804.01280v1
dc.identifier.otherScopus: 85045553013
dc.identifier.urihttp://hdl.handle.net/2299/20252
dc.descriptionThis is an author-created, un-copyedited version of an article published in The Astrophysical Journal. The Version of Record is available online at https://doi.org/10.3847/1538-4357/aab36c
dc.description.abstractWe determine magnesium isotopic abundances of metal-poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleosynthesis in the galactic halo and constrain the timescale of its formation. We observed a sample of eight new halo K dwarfs in a metallicity range of -1.9 < [Fe/H] < -0.9 and 4200 < T eff(K) < 4950, using the HIRES spectrograph at the Keck Observatory (R ≈ 10 5 and 200 ≤ S/N ≤ 300). We obtain magnesium isotopic abundances by spectral synthesis on three MgH features and compare our results with galactic chemical evolution models. With the current sample, we almost double the number of metal-poor stars with Mg isotopes determined from the literature. The new data allow us to determine the metallicity when the 26Mg abundances start to become important, [Fe/H] ∼ -1.4 ± 0.1. The data with [Fe/H] > -1.4 are somewhat higher (1-3σ) than previous chemical evolution model predictions, indicating perhaps higher yields of the neutron-rich isotopes. Our results using only AGB star enrichment suggest a timescale for formation for the galactic halo of about 0.3 Gyr, but considering also supernova enrichment, the upper limit for the timescale formation is about 1.5 Gyr.en
dc.language.isoeng
dc.relation.ispartofThe Astrophysical Journal
dc.rightsOpen
dc.subjectGalaxy: halo
dc.subjectstars: abundances
dc.subjectstars: AGB and post-AGB
dc.subjectAstronomy and Astrophysics
dc.subjectSpace and Planetary Science
dc.titleA formation timescale of the Galactic halo from Mg isotopes in dwarf starsen
dc.contributor.institutionCentre for Astrophysics Research
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.description.statusPeer reviewed
dc.identifier.urlhttp://www.scopus.com/inward/record.url?scp=85045553013&partnerID=8YFLogxK
dc.relation.schoolSchool of Physics, Astronomy and Mathematics
dc.description.versiontypeFinal Accepted Version
dcterms.dateAccepted2018-04-04
rioxxterms.versionAM
rioxxterms.versionofrecordhttps://doi.org/10.3847/1538-4357/aab36c
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue
herts.rights.accesstypeOpen


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