Modelling a high-mass red giant observed by CoRoT

Author(s)

F. Baudin, C. Barban, M. J. Goupil, R. Samadi, Y. Lebreton, H. Bruntt, T. Morel, L. Lefèvre, E. Michel, B. Mosser, F. Carrier, J. De Ridder, A. Hatzes, S. Hekker, T. Kallinger, M. Auvergne, A. Baglin, C. Catala

Abstract

Context. The advent of space-borne photometers such as CoRoT and Kepler

has opened up new fields in asteroseismology. This is especially true

for red giants as only a few of these stars were known to oscillate with

small amplitude, solar-like oscillations before the launch of CoRoT. Aims: The G6 giant HR 2582 (HD 50890) was observed by CoRoT for

approximately 55 days. We present here the analysis of its light curve

and the characterisation of the star using different observables, such

as its location in the Hertzsprung-Russell diagram and seismic

observables. Methods: Mode frequencies are extracted from the

observed Fourier spectrum of the light curve. Numerical stellar models

are then computed to determine the characteristics of the star (mass,

age, etc.) from the comparison with observational constraints.

Results: We provide evidence for the presence of solar-like oscillations

at low frequency, between 10 and 20 μHz, with a regular spacing of

(1.7 ± 0.1) μHz between consecutive radial orders. Only radial

modes are clearly visible. From the models compatible with the

observational constraints used here, We find that HR 2582 (HD 50890) is

a massive star with a mass in the range (3-5 M⊙), clearly

above the red clump. It oscillates with rather low radial order (n =

5-12) modes. Its evolutionary stage cannot be determined with precision:

the star could be on the ascending red giant branch (hydrogen shell

burning) with an age of approximately 155 Myr or in a later phase

(helium burning). In order to obtain a reasonable helium amount, the

metallicity of the star must be quite subsolar. Our best models are

obtained with a mixing length significantly smaller than that obtained

for the Sun with the same physical description (except overshoot). The

amount of core overshoot during the main-sequence phase is found to be

mild, of the order of 0.1 Hp. Conclusions: HR 2582 (HD

50890) is an interesting case as only a few massive stars can be

observed due to their rapid evolution compared to less massive red

giants. HR 2582 (HD 50890) is also one of the few cases that can be used

to validate the scaling relations for massive red giants stars and its

sensitivity to the physics of the star.

 

The CoRoT space mission, launched on 2006 December 27, was developed and

is operated by the CNES with participation of the Science Programs of

ESA; ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain.

Organisation(s)

Department of Art History, Department of Astrophysics

External organisation(s)

Université Paris XI - Paris-Sud, Université de recherche Paris Sciences et Lettres, Université Paris VII - Paris-Diderot, Université de Liège, Katholieke Universiteit Leuven, Thüringer Landessternwarte Tautenburg, University of Birmingham, University of Amsterdam (UvA)

Journal

Astronomy & Astrophysics

Volume

538

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201116967

Publication date

02-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/d7974110-f1ea-4a1f-a9f9-4c76776e0071