Article (Scientific journals)
Observational signatures of past mass-exchange episodes in massive binaries: The case of HD 149 404
Raucq, Françoise; Rauw, Gregor; Gosset, Eric et al.
2016In Astronomy and Astrophysics, 588, p. 10
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Keywords :
stars: early-type; stars: fundamental parameters; binaries: spectroscopic; stars: individual: HD 149 404; stars: massive
Abstract :
[en] Context. Mass and momentum exchanges in close massive binaries play an important role in their evolution, and produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. Aims: We investigated these effects for the detached massive O-star binary HD 149 404 (O7.5 If + ON9.7 I, P = 9.81 days), which is thought to have experienced a past episode of case A Roche-lobe overflow (RLOF). Methods: Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars. The reconstructed primary and secondary spectra were then analysed with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. We complemented the optical study with the study of IUE spectra, which we compare to the synthetic binary spectra. The properties of the stars were compared to evolutionary models. Results: We confirmed a strong overabundance in nitrogen ([N/C] ~ 150[N/C][SUB]⊙[/SUB]) for the secondary and a slight nitrogen overabundance ([N/C] ~ 5[N/C][SUB]⊙[/SUB]) for the primary star. Comparing the two stars, we found evidence for asynchronous rotation, with a rotational period ratio of 0.50 ± 0.11. Conclusions: The hypothesis of a past case A RLOF interaction in HD 149 404 is most plausible to explain its chemical abundances and rotational asynchronicity. Some of the observed properties, such as the abundance pattern, are clearly a challenge for current case A binary evolution models, however.
Research center :
LiSRI - Liège Space Research Institute - ULiège
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Raucq, Françoise ;  Université de Liège > Groupe d'astrophysique des hautes énergies (GAPHE)
Rauw, Gregor  ;  Université de Liège - ULiège
Gosset, Eric ;  Université de Liège > Groupe d'astrophysique des hautes énergies (GAPHE)
Nazé, Yaël  ;  Université de Liège > Groupe d'astrophysique des hautes énergies (GAPHE)
Mahy, Laurent ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS)
Hervé, A.;  Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65, Ondřejov, Czech Republic
Martins, F.;  LUPM, Montpellier University 2, CNRS, place Eugène Bataillon, 34095, Montpellier, France)
Language :
English
Title :
Observational signatures of past mass-exchange episodes in massive binaries: The case of HD 149 404
Publication date :
01 April 2016
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
588
Pages :
A10
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
ARC - Actions de recherche concertées; Etoiles massives
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
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