Reference : The CoRoT target HD 49933 . II. Comparison of theoretical mode amplitudes with observ...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/75542
The CoRoT target HD 49933 . II. Comparison of theoretical mode amplitudes with observations
English
Samadi, R. [Observatoire de Paris, LESIA, CNRS UMR 8109, Université Pierre et Marie Curie, Université Denis Diderot, 5 Pl. J. Janssen, 92195 Meudon, France]
Ludwig, H*-G [Observatoire de Paris, GEPI, CNRS UMR 8111, 5 Pl. J. Janssen, 92195 Meudon, France]
Belkacem, Kevin [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Goupil, M. J. [Observatoire de Paris, LESIA, CNRS UMR 8109, Université Pierre et Marie Curie, Université Denis Diderot, 5 Pl. J. Janssen, 92195 Meudon, France]
Benomar, O. [Institut d'Astrophysique Spatiale, CNRS UMR 8617, Université Paris XI, 91405 Orsay, France]
Mosser, B. [Observatoire de Paris, LESIA, CNRS UMR 8109, Université Pierre et Marie Curie, Université Denis Diderot, 5 Pl. J. Janssen, 92195 Meudon, France]
Dupret, Marc-Antoine [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Baudin, F. [Institut d'Astrophysique Spatiale, CNRS UMR 8617, Université Paris XI, 91405 Orsay, France]
Appourchaux, T. [Institut d'Astrophysique Spatiale, CNRS UMR 8617, Université Paris XI, 91405 Orsay, France]
Michel, Eric [ > > ]
1-Jan-2010
Astronomy and Astrophysics
509
16
Yes
International
[en] convection ; turbulence ; stars: oscillations ; Sun: helioseismology ; stars: individual: HD 49933
[en] Context. The seismic data obtained by CoRoT for the star HD 49933 enable us for the first time to measure directly the amplitudes and linewidths of solar-like oscillations for a star other than the Sun. From those measurements it is possible, as was done for the Sun, to constrain models of the excitation of acoustic modes by turbulent convection. <BR /> Aims: We compare a stochastic excitation model described in Paper I with the asteroseismology data for HD 49933, a star that is rather metal poor and significantly hotter than the Sun. <BR /> Methods: Using the seismic determinations of the mode linewidths detected by CoRoT for HD 49933 and the theoretical mode excitation rates computed in Paper I for the specific case of HD 49933, we derive the expected surface velocity amplitudes of the acoustic modes detected in HD 49933. Using a calibrated quasi-adiabatic approximation relating the mode amplitudes in intensity to those in velocity, we derive the expected values of the mode amplitude in intensity. <BR /> Results: Except at rather high frequency, our amplitude calculations are within 1-Ï error bars of the mode surface velocity spectrum derived with the HARPS spectrograph. The same is found with respect to the mode amplitudes in intensity derived for HD 49933 from the CoRoT data. On the other hand, at high frequency (ν ⪠1.9 mHz), our calculations depart significantly from the CoRoT and HARPS measurements. We show that assuming a solar metal abundance rather than the actual metal abundance of the star would result in a larger discrepancy with the seismic data. Furthermore, we present calculations which assume the â newâ solar chemical mixture to be in better agreement with the seismic data than those that assumed the â oldâ solar chemical mixture. <BR /> Conclusions: These results validate in the case of a star significantly hotter than the Sun and α Cen A the main assumptions in the model of stochastic excitation. However, the discrepancies seen at high frequency highlight some deficiencies of the modelling, whose origin remains to be understood. We also show that it is important to take the surface metal abundance of the solar-like pulsators into account. The CoRoT space mission, launched on December 27 2006, has been developped and is operated by CNES, with the contribution of Austria, Belgium, Brasil, ESA, Germany and Spain.
http://hdl.handle.net/2268/75542
10.1051/0004-6361/200911868
http://adsabs.harvard.edu/abs/2010A%26A...509A..16S
http://de.arxiv.org/abs/0910.4037

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