Modelling of the B-type binaries CW Cephei and U Ophiuchi - A critical view on dynamical masses, core boundary mixing, and core mass

Scientific paper - Original scientific paper

• Author: C. Johnston
• Author: Krešimir Pavlovski
• Author: A. Tkachenko
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics; Astronomy and Astrophysics

Abstract (english)

Context. Intermediate-mass stars are often overlooked. They are not supernova progenitors, but still host convective cores and complex atmospheres that require computationally expensive treatment. This means that there is a general lack of this class of stars modelled by state-of-the-art stellar structure and evolution codes. Aims. We used high-quality spectroscopy to update the dynamically obtained stellar parameters and to produce a new evolutionary assessment of the bright B0.5+B0.5 and B5V+B5V binary systems CW Cep and U Oph. Methods. We used new spectroscopy obtained with the Hermes spectrograph to revisit the photometric binary solution of the two systems. The updated mass ratio and effective temperatures are incorporated to obtain new dynamical masses for the primary and secondary. With these data we performed evolutionary modelling using isochrone-clouds to investigate the core properties of these stars. Results. We report the first abundances for CW Cep and U Oph, and we report an updated dynamical solution for the two systems. We find that we cannot uniquely constrain the amount of core boundary mixing in any of the stars we consider. Instead, we report their core masses and compare our results to previous studies. Conclusions. We find that the per-cent level precision on fundamental stellar quantities are accompanied with core mass estimates to a precision between ∼5% and 15%. We find that differences in analysis techniques can lead to substantially different evolutionary modelling results, which calls for the compilation of a homogeneously analysed sample to draw inferences on internal physical processes.

• Keywords (english): eclipsing binaries; stellar interiros; stellar evolution
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Astronomy and Astrophysics
• Numbering: vol. 628, A25
• p-ISSN: 0004-6361
• e-ISSN: 1432-0746
• DOI: https://doi.org/10.1051/0004-6361/201935235
• URN:NBN: urn:nbn:hr:217:154160
• Publication: 2019
• Type of resource: Text
• Access conditions: Open access
• Public note: © ESO 2019. Received 8 February 2019. Accepted 15 May 2019. Published online 30 July 2019.
• Created on: 2020-07-22 13:37:20