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Article: The planetary nebula abell 48 and its [WN] nucleus

TitleThe planetary nebula abell 48 and its [WN] nucleus
Authors
KeywordsPlanetary nebulae:general
Stars:evolution
abell 48
Planetary nebulae:individual
Stars:wolf-rayet
Issue Date2014
Citation
Monthly Notices of the Royal Astronomical Society, 2014, v. 440, n. 2, p. 1345-1364 How to Cite?
AbstractWe have conducted a detailed multi-wavelength study of the peculiar nebula Abell 48 and its central star. We classify the nucleus as a helium-rich, hydrogen-deficient star of type [WN4-5]. The evidence for either a massive WN or a low-mass [WN] interpretation is critically examined, and we firmly conclude that Abell 48 is a planetary nebula (PN) around an evolved low-mass star, rather than a Population I ejecta nebula. Importantly, the surrounding nebula has a morphology typical of PNe, and is not enriched in nitrogen, and thus not the 'peeled atmosphere' of a massive star. We estimate a distance of 1.6 kpc and a reddening, E(B-V) = 1.90 mag, the latter value clearly showing the nebula lies on the near side of the Galactic bar, and cannot be a massive WN star. The ionized mass (~0.3 M⊙) and electron density (700 cm-3) are typical of middle-aged PNe. The observed stellar spectrum was compared to a grid of models from the Potsdam Wolf-Rayet (PoWR) grid. The best-fitting temperature is 71 kK, and the atmospheric composition is dominated by helium with an upper limit on the hydrogen abundance of 10 per cent. Our results are in very good agreement with the recent study of Todt et al., who determined a hydrogen fraction of 10 per cent and an unusually large nitrogen fraction of ~5 per cent. This fraction is higher than any other low-mass H-deficient star, and is not readily explained by current post-AGB models. We give a discussion of the implications of this discovery for the late-stage evolution of intermediate-mass stars. There is now tentative evidence for two distinct helium-dominated post-AGB lineages, separate to the helium-and carbon-dominated surface compositions produced by a late thermal pulse. Further theoretical work is needed to explain these recent discoveries. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Persistent Identifierhttp://hdl.handle.net/10722/209030
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806

 

DC FieldValueLanguage
dc.contributor.authorFrew, David J.-
dc.contributor.authorBojičić, Ivan S.-
dc.contributor.authorParker, Quentin A.-
dc.contributor.authorStupar, Milorad-
dc.contributor.authorWachter, Stefanie-
dc.contributor.authorDePew, Kyle-
dc.contributor.authorDanehkar, Ashkbiz-
dc.contributor.authorFitzgerald, Michael T.-
dc.contributor.authorDouchin, Dimitri-
dc.date.accessioned2015-03-23T02:31:13Z-
dc.date.available2015-03-23T02:31:13Z-
dc.date.issued2014-
dc.identifier.citationMonthly Notices of the Royal Astronomical Society, 2014, v. 440, n. 2, p. 1345-1364-
dc.identifier.issn0035-8711-
dc.identifier.urihttp://hdl.handle.net/10722/209030-
dc.description.abstractWe have conducted a detailed multi-wavelength study of the peculiar nebula Abell 48 and its central star. We classify the nucleus as a helium-rich, hydrogen-deficient star of type [WN4-5]. The evidence for either a massive WN or a low-mass [WN] interpretation is critically examined, and we firmly conclude that Abell 48 is a planetary nebula (PN) around an evolved low-mass star, rather than a Population I ejecta nebula. Importantly, the surrounding nebula has a morphology typical of PNe, and is not enriched in nitrogen, and thus not the 'peeled atmosphere' of a massive star. We estimate a distance of 1.6 kpc and a reddening, E(B-V) = 1.90 mag, the latter value clearly showing the nebula lies on the near side of the Galactic bar, and cannot be a massive WN star. The ionized mass (~0.3 M⊙) and electron density (700 cm-3) are typical of middle-aged PNe. The observed stellar spectrum was compared to a grid of models from the Potsdam Wolf-Rayet (PoWR) grid. The best-fitting temperature is 71 kK, and the atmospheric composition is dominated by helium with an upper limit on the hydrogen abundance of 10 per cent. Our results are in very good agreement with the recent study of Todt et al., who determined a hydrogen fraction of 10 per cent and an unusually large nitrogen fraction of ~5 per cent. This fraction is higher than any other low-mass H-deficient star, and is not readily explained by current post-AGB models. We give a discussion of the implications of this discovery for the late-stage evolution of intermediate-mass stars. There is now tentative evidence for two distinct helium-dominated post-AGB lineages, separate to the helium-and carbon-dominated surface compositions produced by a late thermal pulse. Further theoretical work is needed to explain these recent discoveries. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.-
dc.languageeng-
dc.relation.ispartofMonthly Notices of the Royal Astronomical Society-
dc.subjectPlanetary nebulae:general-
dc.subjectStars:evolution-
dc.subjectabell 48-
dc.subjectPlanetary nebulae:individual-
dc.subjectStars:wolf-rayet-
dc.titleThe planetary nebula abell 48 and its [WN] nucleus-
dc.typeArticle-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1093/mnras/stu198-
dc.identifier.scopuseid_2-s2.0-84898950358-
dc.identifier.volume440-
dc.identifier.issue2-
dc.identifier.spage1345-
dc.identifier.epage1364-
dc.identifier.eissn1365-2966-

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