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  The Aarhus red giants challenge: I. Stellar structures in the red giant branch phase

Silva Aguirre, V., Christensen-Dalsgaard, J., Cassisi, S., Miller Bertolami, M., Serenelli, A., Stello, D., et al. (2020). The Aarhus red giants challenge: I. Stellar structures in the red giant branch phase. Astronomy and Astrophysics, 635: A164. doi:10.1051/0004-6361/201935843.

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Silva Aguirre, V. , Author
Christensen-Dalsgaard, J., Author
Cassisi, S., Author
Miller Bertolami, M. , Author
Serenelli, A., Author
Stello, D., Author
Weiss, A., Author
Angelou, George C.1, Author              
Jiang, C., Author
Lebreton, Y., Author
Spada, Federico2, Author              
Bellinger, Earl P.1, Author              
Deheuvels, S., Author
Ouazzani, R. M., Author
Pietrinferni, A., Author
Mosumgaard, J. R., Author
Townsend, R. H. D., Author
Battich, T., Author
Bossini, D., Author
Constantino, T., Author
Eggenberger, P., AuthorHekker, Saskia1, Author              Mazumdar, A., AuthorMiglio, A., AuthorNielsen, K. B., AuthorSalaris, M., Author more..
1Max Planck Research Group in Stellar Ages and Galactic Evolution (SAGE), Max Planck Institute for Solar System Research, Max Planck Society, ou_2265636              
2Department Solar and Stellar Interiors, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832287              


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 Abstract: Context. With the advent of space-based asteroseismology, determining accurate properties of red-giant stars using their observed oscillations has become the focus of many investigations due to their implications in a variety of fields in astrophysics. Stellar models are fundamental in predicting quantities such as stellar age, and their reliability critically depends on the numerical implementation of the physics at play in this evolutionary phase. Aims. We introduce the Aarhus red giants challenge, a series of detailed comparisons between widely used stellar evolution and oscillation codes that aim to establish the minimum level of uncertainties in properties of red giants arising solely from numerical implementations. We present the first set of results focusing on stellar evolution tracks and structures in the red-giant-branch (RGB) phase. Methods. Using nine state-of-the-art stellar evolution codes, we defined a set of input physics and physical constants for our calculations and calibrated the convective efficiency to a specific point on the main sequence. We produced evolutionary tracks and stellar structure models at a fixed radius along the red-giant branch for masses of 1.0 M⊙, 1.5 M⊙, 2.0 M⊙, and 2.5 M⊙, and compared the predicted stellar properties. Results. Once models have been calibrated on the main sequence, we find a residual spread in the predicted effective temperatures across all codes of ∼20 K at solar radius and ∼30–40 K in the RGB regardless of the considered stellar mass. The predicted ages show variations of 2–5% (increasing with stellar mass), which we attribute to differences in the numerical implementation of energy generation. The luminosity of the RGB-bump shows a spread of about 10% for the considered codes, which translates into magnitude differences of ∼0.1 mag in the optical V-band. We also compare the predicted [C/N] abundance ratio and find a spread of 0.1 dex or more for all considered masses. Conclusions. Our comparisons show that differences at the level of a few percent still remain in evolutionary calculations of red giants branch stars despite the use of the same input physics. These are mostly due to differences in the energy generation routines and interpolation across opacities, and they call for further investigation on these matters in the context of using properties of red giants as benchmarks for astrophysical studies.


Language(s): eng - English
 Dates: 2020
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/201935843
 Degree: -



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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: 13 Volume / Issue: 635 Sequence Number: A164 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1