On the AGB stars of M4: A robust disagreement between spectroscopic observations and theory

dc.contributor.authorMacLean, B. T.
dc.contributor.authorCampbell, Simon W
dc.contributor.authorAmarsi, Anish M
dc.contributor.authorNordlander, Thomas
dc.contributor.authorCottrell, P L
dc.contributor.authorDe Silva, Gayandhi
dc.contributor.authorLattanzio, John
dc.contributor.authorConstantino, Thomas N
dc.contributor.authorD’Orazi, V
dc.contributor.authorCasagrande, Luca
dc.date.accessioned2019-12-20T02:21:09Z
dc.date.available2019-12-20T02:21:09Z
dc.date.issued2018
dc.date.updated2019-08-04T08:20:22Z
dc.description.abstractSeveral recent spectroscopic investigations have presented conflicting results on the existence of Na-rich asymptotic giant branch (AGB) stars in the Galactic globular cluster M4 (NGC 6121). The studies disagree on whether or not Na-rich red giant branch (RGB) stars evolve to the AGB. For a sample of previously published HERMES/AAT AGB and RGB stellar spectra, we present a re-analysis of O, Na, and Fe abundances, and a new analysis of Mg and Al abundances; we also present CN band strengths for this sample, derived from low-resolution AAOmega spectra. Following a detailed literature comparison, we find that the AGB samples of all studies consistently show lower abundances of Na and Al, and are weaker in CN, than RGB stars in the cluster. This is similar to recent observations of AGB stars in NGC6752 and M62. In an attempt to explain this result, we present new theoretical stellar evolutionary models for M4; however, these predict that all stars, including Na-rich RGB stars, evolve on to the AGB. We test the robustness of our abundance results using a variety of atmospheric models and spectroscopic methods; however, we do not find evidence that systematic modelling uncertainties can explain the apparent lack of Na-rich AGB stars in M4. We conclude that an unexplained, but robust, discordance between observations and theory remains for the AGB stars in M4.en_AU
dc.description.sponsorshipBased in part on data acquired through the AAO, via programs 09B/15, 14B/27, and 15A/21 (PI: Campbell); some of these observations were conducted by Elizabeth Wylie de Boer, Richard Stancliffe, and George Angelou. Part of this work was supported by the DAAD (PPP project 57219117) with funds from the German Federal Ministry of Education and Research (BMBF). Parts of this research were conducted by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. BTM acknowledges the financial support of the Research Training Program (RTP) scheme scholarship. SWC acknowledges federal funding from the Australian Research Council though the Future Fellowship grant entitled ‘Where are the Convective Boundaries in Stars?’ (FT160100046). AMA acknowledges funds from the Alexander von Humboldt Foundation in the framework of the Sofja Kovalevskaja Award endowed by the Federal Ministry of Education and Research. TN acknowledges funding from the Australian Research Council (grant DP150100250). VD acknowledges support from the AAO distinguished visitor programme 2016. LC gratefully acknowledges support from the Australian Research Council (grants DP150100250, FT160100402). This work was supported by computational resources provided by the Australian Government through the National Computational Infrastructure (NCI) under the National Computational Merit Allocation Scheme (project ew6).en_AU
dc.format.mimetypeapplication/pdfen_AU
dc.identifier.issn0035-8711en_AU
dc.identifier.urihttp://hdl.handle.net/1885/196424
dc.language.isoen_AUen_AU
dc.provenancehttp://sherpa.ac.uk/romeo/issn/0035-8711/..."author can archive publisher's version/PDF" from SHERPA/RoMEO site (as at 20/12/19). This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.en_AU
dc.publisherOxford University Pressen_AU
dc.relationhttp://purl.org/au-research/grants/arc/CE170100013en_AU
dc.relationhttp://purl.org/au-research/grants/arc/FT160100046en_AU
dc.relationhttp://purl.org/au-research/grants/arc/FT160100402en_AU
dc.relationhttp://purl.org/au-research/grants/arc/DP150100250en_AU
dc.rights© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Societyen_AU
dc.sourceMonthly Notices of the Royal Astronomical Societyen_AU
dc.titleOn the AGB stars of M4: A robust disagreement between spectroscopic observations and theoryen_AU
dc.typeJournal articleen_AU
dcterms.accessRightsOpen Accessen_AU
local.bibliographicCitation.issue1en_AU
local.bibliographicCitation.lastpage395en_AU
local.bibliographicCitation.startpage373en_AU
local.contributor.affiliationMacLean, B. T., Monash Universityen_AU
local.contributor.affiliationCampbell, Simon W, Monash Universityen_AU
local.contributor.affiliationAmarsi, Anish M, Max Planck Institute for Astronomyen_AU
local.contributor.affiliationNordlander, Thomas, College of Science, ANUen_AU
local.contributor.affiliationCottrell, P L, University of Canterburyen_AU
local.contributor.affiliationDe Silva, Gayandhi, Australian Astronomical Observatoryen_AU
local.contributor.affiliationLattanzio, John, Monash Universityen_AU
local.contributor.affiliationConstantino, Thomas N, Monash Universityen_AU
local.contributor.affiliationD’Orazi , V, Macquarie Universityen_AU
local.contributor.affiliationCasagrande, Luca, College of Science, ANUen_AU
local.contributor.authoremailu5209059@anu.edu.auen_AU
local.contributor.authoruidNordlander, Thomas, u1019177en_AU
local.contributor.authoruidCasagrande, Luca, u5209059en_AU
local.description.notesImported from ARIESen_AU
local.identifier.absfor020104 - Galactic Astronomyen_AU
local.identifier.absfor020110 - Stellar Astronomy and Planetary Systemsen_AU
local.identifier.absseo970102 - Expanding Knowledge in the Physical Sciencesen_AU
local.identifier.ariespublicationu4485658xPUB2593en_AU
local.identifier.citationvolume481en_AU
local.identifier.doi10.1093/mnras/sty2297en_AU
local.identifier.scopusID2-s2.0-85054079651
local.identifier.uidSubmittedByu4485658en_AU
local.publisher.urlhttps://academic.oup.com/en_AU
local.type.statusPublished Versionen_AU

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