000005486 001__ 5486
000005486 005__ 20211216211305.0
000005486 0247_ $$2DOI$$a10.1051/0004-6361/202040195
000005486 037__ $$aSCART-2021-0146
000005486 100__ $$aAbdul-Masih, Michael
000005486 245__ $$aConstraining the overcontact phase in massive binary evolution. I. Mixing in V382 Cyg, VFTS 352, and OGLE SMC-SC10 108086
000005486 260__ $$c2021
000005486 520__ $$aContext. As potential progenitors of several exotic phenomena including gravitational wave sources, magnetic stars, and Be stars, close massive binary systems probe a crucial area of the parameter space in massive star evolution. Despite the importance of these systems, large uncertainties regarding the nature and efficiency of the internal mixing mechanisms still exist.  Aims: We aim to provide robust observational constraints on the internal mixing processes by spectroscopically analyzing a sample of three massive overcontact binaries at different metallicities.  Methods: Using optical phase-resolved spectroscopic data, we performed an atmosphere analysis using more traditional 1D techniques and the most recent 3D techniques. We compared and contrasted the assumptions and results of each technique and investigated how the assumptions affect the final derived atmospheric parameters.  Results: We find that in all three cases, both components of a system are highly overluminous, indicating either efficient internal mixing of helium or previous nonconservative mass transfer. However, we do not find strong evidence of the helium or CNO surface abundance changes that are usually associated with mixing. Additionally, we find that in unequal-mass systems, the measured effective temperature and luminosity of the less massive component places it very close to the more massive component on the Hertzsprung-Russell diagram. These results were obtained independently using both of the techniques mentioned above. This suggests that these measurements are robust.  Conclusions: The observed discrepancies between the temperature and the surface abundance measurements when compared to theoretical expectations indicate that additional physical mechanisms that have not been accounted for so far may be at play.
000005486 594__ $$aNO
000005486 700__ $$aSana, Hugues
000005486 700__ $$aHawcroft, Calum
000005486 700__ $$aAlmeida, Leonardo A.
000005486 700__ $$aBrands, Sarah A.
000005486 700__ $$ade Mink, Selma E.
000005486 700__ $$aJustham, Stephen
000005486 700__ $$aLanger, Norbert
000005486 700__ $$aMahy, Laurent
000005486 700__ $$aMarchant, Pablo
000005486 700__ $$aMenon, Athira
000005486 700__ $$aPuls, Joachim
000005486 700__ $$aSundqvist, Jon
000005486 773__ $$c27$$nA96$$pAstronomy & Astrophysics$$v651$$y2021
000005486 8560_ $$flaurent.mahy@ksb-orb.be
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000005486 905__ $$apublished in
000005486 980__ $$aREFERD