Reference : Amplitudes of solar-like oscillations in red giant stars. Evidence for non-adiabatic ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/140181
Amplitudes of solar-like oscillations in red giant stars. Evidence for non-adiabatic effects using CoRoT observations
English
Samadi, R. mailto [LESIA, CNRS UMR 8109, Observatoire de Paris, Université Pierre et Marie Curie, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France]
Belkacem, K. [LESIA, CNRS UMR 8109, Observatoire de Paris, Université Pierre et Marie Curie, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France]
Dupret, Marc-Antoine mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117, Heidelberg, Germany; GEPI, CNRS, Observatoire de Paris, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France]
Baudin, F. [Institut d'Astrophysique Spatiale, CNRS, Université Paris XI, 91405, Orsay Cedex, France]
Caffau, E. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117, Heidelberg, Germany; GEPI, CNRS, Observatoire de Paris, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France]
Goupil, M.-J. [LESIA, CNRS UMR 8109, Observatoire de Paris, Université Pierre et Marie Curie, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France]
Barban, C. [LESIA, CNRS UMR 8109, Observatoire de Paris, Université Pierre et Marie Curie, Université Denis Diderot, Place Jules Janssen, 92195, Meudon Cedex, France)]
1-Jul-2012
Astronomy and Astrophysics
543
120
Yes
International
[en] stars: solar-type ; stars: oscillations ; sun: oscillations ; turbulence ; convection ; waves
[en] Context. A growing number of solar-like oscillations has been detected in red giant stars thanks to the CoRoT and Kepler space-crafts. In the same way as for main-sequence stars, mode driving is attributed to turbulent convection in the uppermost convective layers of those stars. <BR /> Aims: The seismic data gathered by CoRoT on red giant stars allow us to test the mode driving theory in physical conditions different from main-sequence stars. <BR /> Methods: Using a set of 3D hydrodynamical models representative of the upper layers of sub- and red giant stars, we computed the acoustic mode energy supply rate ({p_max}). Assuming adiabatic pulsations and using global stellar models that assume that the surface stratification comes from the 3D hydrodynamical models, we computed the mode amplitude in terms of surface velocity. This was converted into intensity fluctuations using either a simplified adiabatic scaling relation or a non-adiabatic one. <BR /> Results: From L and M (the luminosity and mass), the energy supply rate {p_max} is found to scale as (L/M)[SUP]2.6[/SUP] for both main-sequence and red giant stars, extending previous results. The theoretical amplitudes in velocity under-estimate the Doppler velocity measurements obtained so far from the ground for red giant stars by about 30%. In terms of intensity, the theoretical scaling law based on the adiabatic intensity-velocity scaling relation results in an under-estimation by a factor of about 2.5 with respect to the CoRoT seismic measurements. On the other hand, using the non-adiabatic intensity-velocity relation significantly reduces the discrepancy with the CoRoT data. The theoretical amplitudes remain 40% below, however, the CoRoT measurements. <BR /> Conclusions: Our results show that scaling relations of mode amplitudes cannot be simply extended from main-sequence to red giant stars in terms of intensity on the basis of adiabatic relations because non-adiabatic effects for red giant stars are important and cannot be neglected. We discuss possible reasons for the remaining differences.
http://hdl.handle.net/2268/140181
10.1051/0004-6361/201219253
http://adsabs.harvard.edu/abs/2012A%26A...543A.120S
http://de.arxiv.org/abs/1205.4846

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