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

• Autores: Silva Aguirre, V.; Christensen Dalsgaard, Jorgen; Cassisi, S.; Miller Bertolami, Marcelo Miguel; Serenelli, Aldo; Stello, D.; Weiss, A.; Angelou, G.; iang, C.; Lebreton, Y.; Spada, F.; Bellinger, E. P.; Deheuvels, S.; Ouazzani, R. M.; Pietrinferni, A.; Mosumgaard, J. R.; Townsend, R. H. D.; Battich, Tiara; Bossini, D.; Constantino, T.; Eggenberger, P.; Hekker, S.; Mazumdar, A.; Miglio, A.; Nielsen, K.B.; Salaris, M.
• Año de publicación: 2020
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: stars: evolution; asteroseismology; stars: interiors
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

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.
Fil: Silva Aguirre, V.. Aarhus University; Dinamarca
Fil: Christensen Dalsgaard, Jorgen. Aarhus University; Dinamarca
Fil: Cassisi, S.. INAF. Astronomical Observatory of Abruzzo; Italia
Fil: Miller Bertolami, Marcelo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Serenelli, Aldo. Instituto de Ciencias del Espacio; España
Fil: Stello, D.. University of New South Wales; Australia
Fil: Weiss, A.. Max-Planck-Institut für Astrophysics; Alemania
Fil: Angelou, G.. University of New South Wales; Australia
Fil: iang, C.. Sun Yat-Sen University; China
Fil: Lebreton, Y.. Sorbonne Université; Francia
Fil: Spada, F.. Max-Planck-Institut für Sonnensystemforschung; Alemania
Fil: Bellinger, E. P.. Max-Planck-Institut für Sonnensystemforschung; Alemania
Fil: Deheuvels, S.. Université de Toulouse; Francia
Fil: Ouazzani, R. M.. Sorbonne Université; Francia
Fil: Pietrinferni, A.. Astronomical Observatory of Abruzzo; Italia
Fil: Mosumgaard, J. R.. Aarhus University; Dinamarca
Fil: Townsend, R. H. D.. Department of Astronomy; Estados Unidos
Fil: Battich, Tiara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Bossini, D.. Aarhus University; Dinamarca
Fil: Constantino, T.. University of Exeter; Reino Unido
Fil: Eggenberger, P.. Université de Genève; Suiza
Fil: Hekker, S.. Aarhus University; Dinamarca
Fil: Mazumdar, A.. Homi Bhabha Centre for Science Education; India
Fil: Miglio, A.. Aarhus University; Dinamarca
Fil: Nielsen, K.B.. Aarhus University; Dinamarca
Fil: Salaris, M.. Liverpool John Moores University;