The Aarhus red giants challenge: II. Stellar oscillations in the red giant branch phase

J. Christensen-Dalsgaard (1) , V. Silva Aguirre (2) , S. Cassisi , M. Miller Bertolami , A. Serenelli (3) , D. Stello (4) , A. Weiss (5) , G. Angelou , C. Jiang , Y. Lebreton (6, 7) , F. Spada (8) , E. Bellinger , S. Deheuvels (9) , R. Ouazzani (6) , A. Pietrinferni (10) , J. Mosumgaard , R. H D Townsend (11) , T. Battich , D. Bossini (12) , T. Constantino , P. Eggenberger (13) , S. Hekker (14) , A. Mazumdar , A. Miglio (15) , K. Nielsen , M. Salaris (16)

1 SAC - Stellar Astrophysics Centre [Aarhus]
2 KITP - Kavli Institute for Theoretical Physics [Santa Barbara]
3 ICE-CSIC - Institute of Space Sciences [Barcelona]
4 UNSW - School of Physics [UNSW Sydney]
5 Max Planck Institute for Astrophysics
6 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics
7 IPR - Institut de Physique de Rennes
8 INFN - Istituto Nazionale di Fisica Nucleare [Pisa]
9 IRAP - Institut de recherche en astrophysique et planétologie
10 Collurania Astronomical Observatory
11 University of Wisconsin-Madison
12 OAPD - INAF - Osservatorio Astronomico di Padova
13 ObsGE - Observatoire Astronomique de l'Université de Genève
14 School of Physics and Astronomy
15 Institut d'Astrophysique et de Géophysique [Liège]
16 Astrophysical Research Institute [Liverpool]

Context. The large quantity of high-quality asteroseismic data that have been obtained from space-based photometric missions and the accuracy of the resulting frequencies motivate a careful consideration of the accuracy of computed oscillation frequencies of stellar models, when applied as diagnostics of the model properties. Aims. Based on models of red-giant stars that have been independently calculated using different stellar evolution codes, we investigate the extent to which the differences in the model calculation affect the model oscillation frequencies and other asteroseismic diagnostics. Methods. For each of the models, which cover four different masses and different evolution stages on the red-giant branch, we computed full sets of low-degree oscillation frequencies using a single pulsation code and, from these frequencies, typical asteroseismic diagnostics. In addition, we carried out preliminary analyses to relate differences in the oscillation properties to the corresponding model differences. Results. In general, the differences in asteroseismic properties between the different models greatly exceed the observational precision of these properties. This is particularly true for the nonradial modes whose mixed acoustic and gravity-wave character makes them sensitive to the structure of the deep stellar interior and, hence, to details of their evolution. In some cases, identifying these differences led to improvements in the final models presented here and in Paper I; here we illustrate particular examples of this. Conclusions. Further improvements in stellar modelling are required in order fully to utilise the observational accuracy to probe intrinsic limitations in the modelling and improve our understanding of stellar internal physics. However, our analysis of the frequency differences and their relation to stellar internal properties provides a striking illustration of the potential, in particular, of the mixed modes of red-giant stars for the diagnostics of stellar interiors.

Domaines: Physique [physics]; Astrophysique stellaire et solaire [astro-ph.SR]

J. Christensen-Dalsgaard, V. Silva Aguirre, S. Cassisi, M. Miller Bertolami, A. Serenelli, et al.. The Aarhus red giants challenge: II. Stellar oscillations in the red giant branch phase. Astronomy and Astrophysics - A&A, 2020, 635, pp.A165. ⟨10.1051/0004-6361/201936766⟩. ⟨hal-02523041⟩