A grid of MARCS model atmospheres for S stars

S-type stars are late-type giants whose atmosphere is enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing AGB. A large grid of S-star model atmospheres has been computed covering the...

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Bibliographic Details
Published in:arXiv.org 2010-11
Main Authors: Sophie Van Eck, Neyskens, Pieter, Plez, Bertrand, Jorissen, Alain, Edvardsson, Bengt, Eriksson, Kjell, Gustafsson, Bengt, Jorgensen, Uffe-Grae, Nordlund, Ake
Format: Article
Language:English
Subjects:
Companion stars
Nuclear fusion
Photometry
S stars
Stellar atmospheres
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Summary:S-type stars are late-type giants whose atmosphere is enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing AGB. A large grid of S-star model atmospheres has been computed covering the range 2700 < Teff < 4000 K with 0.5 < C/O < 0.99. ZrO and TiO band strength indices as well as VJHKL photometry are needed to disentangle Teff, C/O and [s/Fe]. A "best-model finding tool" was developed using a set of well-chosen indices and checked against photometry as well as low- and high-resolution spectroscopy. It is found that applying M-star model atmospheres (i.e., with a solar C/O ratio) to S stars can lead to errors on Teff up to 400K. We constrain the parameter space occupied by S stars of the vast sample of Henize stars in terms of Teff, [C/O] and [s/Fe].
ISSN:2331-8422