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dc.contributor.authorNaidu, R.P.
dc.contributor.authorJi, A.P.
dc.contributor.authorConroy, C.
dc.contributor.authorBonaca, A.
dc.contributor.authorTing, Y.-S.
dc.contributor.authorZaritsky, D.
dc.contributor.authorVan Son, L.A.C.
dc.contributor.authorBroekgaarden, F.S.
dc.contributor.authorTacchella, S.
dc.contributor.authorChandra, V.
dc.contributor.authorCaldwell, N.
dc.contributor.authorCargile, P.
dc.contributor.authorSpeagle, J.S.
dc.date.accessioned2022-04-11T23:18:08Z
dc.date.available2022-04-11T23:18:08Z
dc.date.issued2022
dc.identifier.citationNaidu, R. P., Ji, A. P., Conroy, C., Bonaca, A., Ting, Y.-S., Zaritsky, D., Van Son, L. A. C., Broekgaarden, F. S., Tacchella, S., Chandra, V., Caldwell, N., Cargile, P., & Speagle, J. S. (2022). Evidence from Disrupted Halo Dwarfs that r-process Enrichment via Neutron Star Mergers is Delayed by 3500 Myr. Astrophysical Journal Letters.
dc.identifier.issn2041-8205
dc.identifier.doi10.3847/2041-8213/ac5589
dc.identifier.urihttp://hdl.handle.net/10150/663949
dc.description.abstractThe astrophysical origins of r-process elements remain elusive. Neutron star mergers (NSMs) and special classes of core-collapse supernovae (rCCSNe) are leading candidates. Due to these channels' distinct characteristic timescales (rCCSNe: prompt, NSMs: delayed), measuring r-process enrichment in galaxies of similar mass but differing star formation durations might prove informative. Two recently discovered disrupted dwarfs in the Milky Way's stellar halo, Kraken and Gaia-Sausage Enceladus (GSE), afford precisely this opportunity: Both have M ⋆ ≈ 108 M ⊙ but differing star formation durations of ≈2 Gyr and ≈3.6 Gyr. Here we present R ≈ 50,000 Magellan/MIKE spectroscopy for 31 stars from these systems, detecting the r-process element Eu in all stars. Stars from both systems have similar [Mg/H] ≈ -1, but Kraken has a median [Eu/Mg] ≈ -0.1 while GSE has an elevated [Eu/Mg] ≈ 0.2. With simple models, we argue NSM enrichment must be delayed by 500-1000 Myr to produce this difference. rCCSNe must also contribute, especially at early epochs, otherwise stars formed during the delay period would be Eu free. In this picture, rCCSNe account for ≈50% of the Eu in Kraken, ≈25% in GSE, and ≈15% in dwarfs with extended star formation durations like Sagittarius. The inferred delay time for NSM enrichment is 10×-100× longer than merger delay times from stellar population synthesis - this is not necessarily surprising because the enrichment delay includes time taken for NSM ejecta to be incorporated into subsequent generations of stars. For example, this may be due to natal kicks that result in r-enriched material deposited far from star-forming gas, which then takes ≈108-109 yr to cool in these galaxies. © 2022. The Author(s). Published by the American Astronomical Society.
dc.language.isoen
dc.publisherAmerican Astronomical Society
dc.rightsCopyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.titleEvidence from Disrupted Halo Dwarfs that r-process Enrichment via Neutron Star Mergers is Delayed by 3500 Myr
dc.typeArticle
dc.typetext
dc.contributor.departmentSteward Observatory, University of Arizona
dc.identifier.journalAstrophysical Journal Letters
dc.description.noteOpen access journal
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.
dc.eprint.versionFinal published version
dc.source.journaltitleAstrophysical Journal Letters
refterms.dateFOA2022-04-11T23:18:08Z


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Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.
Except where otherwise noted, this item's license is described as Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.