Binary stars in the Galactic thick disc
Publication Date
2018-01Journal Title
Monthly Notices of the Royal Astronomical Society
ISSN
0035-8711
Publisher
Oxford University Press (OUP)
Volume
473
Issue
3
Pages
2984-2999
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Izzard, R., Preece, H., Jofre, P., Halabi, G., Masseron, T., & Tout, C. (2018). Binary stars in the Galactic thick disc. Monthly Notices of the Royal Astronomical Society, 473 (3), 2984-2999. https://doi.org/10.1093/mnras/stx2355
Abstract
The combination of asteroseismologically-measured masses with abundances from
detailed analyses of stellar atmospheres challenges our fundamental knowledge
of stars and our ability to model them. Ancient red-giant stars in the Galactic
thick disc are proving to be most troublesome in this regard. They are older
than 5 Gyr, a lifetime corresponding to an initial stellar mass of about
$1.2{\mathrm{M}_{\odot}}$. So why do the masses of a sizeable fraction of
thick-disc stars exceed $1.3{\mathrm{M}_{\odot}}$, with some as massive as
$2.3{\mathrm{M}_{\odot}}$ ? We answer this question by considering duplicity in
the thick-disc stellar population using a binary population-nucleosynthesis
model. We examine how mass transfer and merging affect the stellar mass
distribution and surface abundances of carbon and nitrogen. We show that a few
per cent of thick-disc stars can interact in binary star systems and become
more massive than $1.3{\mathrm{M}_{\odot}}$. Of these stars, most are single
because they are merged binaries. Some stars more massive than
$1.3{\mathrm{M}_{\odot}}$ form in binaries by wind mass transfer. We compare
our results to a sample of the APOKASC data set and find reasonable agreement
except in the number of these thick-disc stars more massive than
$1.3{\mathrm{M}_{\odot}}$. This problem is resolved by the use of a
logarithmically-flat orbital-period distribution and a large binary fraction.
Sponsorship
Science and Technology Facilities Council (ST/L003910/1)
Science and Technology Facilities Council (ST/M003892/1)
European Research Council (320360)
Science and Technology Facilities Council (ST/N000927/1)
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.1093/mnras/stx2355
This record's URL: https://www.repository.cam.ac.uk/handle/1810/274811
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