Reference : Chemical abundances of fast-rotating massive stars. II. Interpretation and comparison...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/215267
Chemical abundances of fast-rotating massive stars. II. Interpretation and comparison with evolutionary models
English
Cazorla, Constantin mailto [Université de Liège - ULiège > > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Nazé, Yaël mailto [Université de Liège - ULiège > > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Morel, Thierry mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Georgy, Cyril mailto [Observatoire de Genève, Université de Genève > > Evolution Stellaire > >]
Godart, Mélanie mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Langer, Norbert mailto [Argelander-Institut für Astronomie der Universität Bonn > > AIfA Stellar Physics Group > >]
Aug-2017
Astronomy and Astrophysics
EDP Sciences
604
A123
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] stars:abundances ; stars:early-type ; stars:fundamentalparameters ; stars:massive ; stars:rotation
[en] Aims: Past observations of fast-rotating massive stars exhibiting normal nitrogen abundances at their surface have raised questions about the rotational mixing paradigm. We revisit this question thanks to a spectroscopic analysis of a sample of bright fast-rotating OB stars, with the goal of quantifying the efficiency of rotational mixing at high rotation rates.
Methods: Our sample consists of 40 fast rotators on the main sequence, with spectral types comprised between B0.5 and O4. We compare the abundances of some key element indicators of mixing (He, CNO) with the predictions of evolutionary models for single objects and for stars in interacting binary systems.
Results: The properties of half of the sample stars can be reproduced by single evolutionary models, even in the case of probable or confirmed binaries that can therefore be true single stars in a pre-interaction configuration. The main problem for the rest of the sample is a mismatch for the [N/O] abundance ratio (we confirm the existence of fast rotators with a lack of nitrogen enrichment) and/or a high helium abundance that cannot be accounted for by models. Modifying the diffusion coefficient implemented in single- star models does not solve the problem as it cannot simultaneously reproduce the helium abundances and [N/O] abundance ratios of our targets. Since part of them actually are binaries, we also compared their chemical properties with predictions for post-mass transfer systems. We found that these models can explain the abundances measured for a majority of our targets, including some of the most helium-enriched, but fail to reproduce them in other cases. Our study thus reveals that some physical ingredients are still missing in current models.
PRODEX XMM, ARC grant for concerted research actions financed by the French community of Bel- gium (Wallonia-Brussels federation)
Researchers ; Professionals ; Students
http://hdl.handle.net/2268/215267
10.1051/0004-6361/201730680

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