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Helium and nitrogen enrichment in massive main-sequence stars: mechanisms and implications for the origin of WNL stars

Roy, Arpita; Sutherland, Ralph; Krumholz, Mark; Heger, Alexander; Dopita, Michael

Description

The evolutionary paths taken by massive stars with M 60 M remain substantially uncertain. They begin their lives as main-sequence (MS) O stars. Depending on their masses, rotation rates, and metallicities, they can then encounter a wide range of evolutionary states with an equally broad set of possible surface compositions and spectral classifications. We present a new grid of calculations for the evolution of such stars that covers a broad range in mass, M/M = 60-150, rotation rate, v/vcrit...[Show more]

dc.contributor.authorRoy, Arpita
dc.contributor.authorSutherland, Ralph
dc.contributor.authorKrumholz, Mark
dc.contributor.authorHeger, Alexander
dc.contributor.authorDopita, Michael
dc.date.accessioned2022-07-18T01:11:12Z
dc.date.available2022-07-18T01:11:12Z
dc.identifier.issn0035-8711
dc.identifier.urihttp://hdl.handle.net/1885/269741
dc.description.abstractThe evolutionary paths taken by massive stars with M 60 M remain substantially uncertain. They begin their lives as main-sequence (MS) O stars. Depending on their masses, rotation rates, and metallicities, they can then encounter a wide range of evolutionary states with an equally broad set of possible surface compositions and spectral classifications. We present a new grid of calculations for the evolution of such stars that covers a broad range in mass, M/M = 60-150, rotation rate, v/vcrit = 0-0.6, metallicity, [Fe/H] = −4 to 0, and α-element enhancement, [α/Fe] = 0-0.4. We show that rotating stars undergo rotationally induced dredgeup of nucleosynthetic products, mostly He and N, to their surfaces while still on the MS. Nonrotating metal-rich stars also reveal the products of nucleosynthesis on their surfaces because even modest amounts of mass-loss expose their 'fossil' convective cores: regions that are no longer convective, but were part of the convective core at an early stage in the star's evolution. Thus, surface enhancement of He and N is expected for rotating stars at all metallicities, and for non-rotating stars if they are relatively metal-rich. We calculate a stellar atmosphere for a representative model from our grid, properly accounting for He and N enhancement, and show that the resulting spectrum provides a good match to observed WNL stars, strongly suggesting that the physical mechanisms we have identified are the ultimate cause of the WNL phase.
dc.description.sponsorshipAuthors acknowledge the valuable and constructive comments from the anonymous referee. AR and MRK acknowledge support from the Australian Research Council’s Discovery Projects and Future Fellowship funding scheme, awards DP160100695 and FT180100375. RSS and MAD acknowledge the support of the Australian Research Council Centre of Excellence for All Sky As trophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. AR acknowledges Charlie Conroy, Aaron Dotter, and Jieun Choi for providing the MIST-II set-up and many useful discussions. AR gratefully acknowledges the support of Lisa Kewley’s ARC Laureate Fellowship (FL150100113). AH has been supported, in part, by a grant from Science and Technology Commission of Shanghai Municipality (Grants No.16DZ2260200) and National Natural Science Foundation of China (Grants No.11655002), and by the Australian Research Council through a Future Fellowship (FT120100363). This work benefited from support by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements).
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherOxford University Press
dc.rights© 2020 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
dc.sourceMonthly Notices of the Royal Astronomical Society
dc.subjectstars: abundances
dc.subjectstars: massive
dc.subjectstars: mass-loss
dc.subjectISM: abundances
dc.subjectgalaxies: high-redshift
dc.subjectgalaxies: ISM
dc.titleHelium and nitrogen enrichment in massive main-sequence stars: mechanisms and implications for the origin of WNL stars
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume494
dc.date.issued2020
local.identifier.absfor000000 - Internal ANU use only
local.identifier.ariespublicationa383154xPUB13634
local.publisher.urlhttp://mnras.oxfordjournals.org/
local.type.statusPublished Version
local.contributor.affiliationRoy, Arpita, College of Science, ANU
local.contributor.affiliationSutherland, Ralph, College of Science, ANU
local.contributor.affiliationKrumholz, Mark, College of Science, ANU
local.contributor.affiliationHeger, Alexander, Monash University
local.contributor.affiliationDopita, Michael, College of Science, ANU
dc.relationhttp://purl.org/au-research/grants/arc/DP160100695
dc.relationhttp://purl.org/au-research/grants/arc/FT180100375
dc.relationhttp://purl.org/au-research/grants/arc/CE170100013
dc.relationhttp://purl.org/au-research/grants/arc/FL150100113
dc.relationhttp://purl.org/au-research/grants/arc/FT120100363
local.bibliographicCitation.issue3
local.bibliographicCitation.startpage3861
local.bibliographicCitation.lastpage3879
local.identifier.doi10.1093/mnras/staa781
dc.date.updated2021-08-01T08:22:46Z
dcterms.accessRightsOpen Access
dc.provenancehttps://v2.sherpa.ac.uk/id/publication/24618..."The Published Version can be archived in an Institutional Repository" from SHERPA/RoMEO site (as at 18/07/2022). This article has been accepted for publication in [Monthly Notices of the Royal Astronomical Society] ©: 2020 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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