Observations of Red Giants in the NGC 6633 cluster by the Space Mission CoRoT C. Barban 1 F. Baudin 2, E. Poretti 3, B. Mosser 1, S. Hekker 4, Th. Kallinger 5, A. Miglio 6, J. Montalban 7, T. Morel 7, Ph. Mathias 8 1 LESIA/UFE, Observatoire de Paris, France 2 IAS, Univ. Paris XI, France 3 INAF, Osservatorio Astronomico di Brera, Italy 4 Astronomical Institute Anton Pannekoek, Univ. of Amsterdam, TheNetherlands 5 Institute voor Sterrenkunde, Univ. Leuven, Belgium 6 School of Physics and Astronomy, Univ. of Birmingham, GB 7 Institut d Astrophysique et de Géophysique, Univ. de Liège, Belgium 8 IRAP, Univ. de Toulouse, France 1
Solar-like oscillations in red giants http://www.bramboroson.com/astro/images/hrdiagram.jpg Amplitude > 10 ppm or m/s Period > hours Amplitudes larger than for the Sun Interesting targets for studying stars with different internal structure 2
However, Red Giants were not among the priority targets of CoRoT! Why? A little bit of history 3
During the preparatory phase of the COROT space mission at the beggining of 2000 s Magali Deluil COROT Exoplanet Working Group Eric Michel COROT Seismology Working Group We don t want Red Giants as CoRoT targets since we don t expect earth-like planets around these kind of stars! We don t want Red giants as CoRoT targets because 4
Non radial modes strongly damped in Red Giants First clear evidence of solar-like Hya oscillation spectrum oscillations in a red giant by Frandsen et al. 2002 on Hya: Only radial modes detected. Radial modes are expected to dominate the oscillation spectrum of a Red Giant according to: Dziembowski et al. 1977 Dziembowski et al. 2001 Gough & Houdek 2002 non-radial modes strongly damped due to the high density contract between the core and the envelope. 5
+ controversial results from space Oph oscillation spectrum Only radial modes by Barban et al. (2007) Or radial and non-radial modes by Kallinger et al. (2008) and Hekker et al. (2006) 6
leading to a concern about asteroseismology of Red Giants 7
And here comes COROT 0 0 1 2 0 1 2 1 2 1 2 0 8
The wealth of results obtained from seismology of red giants by CoRoT and Kepler is an extraordinary and unexpected gift to stellar physics! 9
HR diagram of Red Giants observed by CoRoT Chaplin & Miglio 2013 10
HR diagram of Red Giants observed by CoRoT NGC 6633 Chaplin & Miglio 2013 11
The NGC 6633 open cluster Distance = 375 pc (van Leeuwen 2009) -0.096<[Fe/H]<-0.04 (Jeffreis et al. 2002, Pauzen et al. 2010) HD 170031 12
Why observing cluster stars? Stars in an open cluster: same distance same age same initial composition See e.g. with Kepler data: Miglio et al. (2012) Stello et al. (2011a) Stello et al. (2011b) Basu et al. (2011), 13
Red giants in NGC6633: CoRoT light curves 2 consecutive long Runs ~ 176 days 14
ed giants in NGC6633: CoRoT oscillation spectrum 15
ed giants in NGC6633: CoRoT oscillation spectrum HD170200 is not a Red Giant with solar-like oscillations BUT a classical pulsator (B)!! 16
Mass and radius from seismic indices (e.g. Kjeldsen & Bedding 1995, Kallinger et al. 2010, Belkacem et al. 2011) Sun (Chaplin et al. 2011) : Δν = 134.9 μhz ν max = 3.15 mhz Teff = 5777 K Chaplin et al. 2011 17
Red giants in NGC6633: seismic indices By using an EACF (Envelop Autocorrelation Function) method (Mosser & Appourchaux 2010) In agreement with values obtained by other methods by S. Hekker and Th. Kallinger HD 170174 Δν ~ 4.17 μhz ν max ~ 44.56 μhz M ~ 3M R ~ 14R HD 170053 Δν ~ 1.09 μhz ν max ~ 9.18 μhz M ~ 4M R ~ 39R HD 170031 Δν ~ 3.87 μhz ν max ~ 39 μhz M ~ 2M R ~ 14R M clump ~2.8M HD170031 is probably a clump star but then has a too low mass HD 170031 not a cluster member HD 170231 Δν ~ 5.33 μhz ν max ~ 66 μhz M ~ 3M R ~ 13R 18
Spectroscopic data ESO, La silla, Chile PI: E. Poretti Simultaneous bi-site observations OHP, France PI: Ph. Mathias Radial velocity of +16 km/s vs -28 km/s for the cluster + Barium abundance HD 170031 not a cluster member
ed giants in NGC6633: CoRoT oscillation spectrum 3 Red Giants with solar-like oscillations 20
Red giants in NGC6633: atmospheric parameters HD 170174 Teff (K) logg [Fe/H] 5035 2.74-0.01 5055 2.56-0.07 HD 170053 Teff (K) logg [Fe/H] 4315 1.72-0.14 4290 1.85-0.03 Spectroscopic data Spectroscopic + seismic data following Morel & Miglio et al. 2012 HD 170053 discrepant in terms of [Fe/H] with logg from spectroscopic data but NOT when logg fixed to seismic data. HD 170231 Teff (K) logg [Fe/H] 5150 2.96 +0.04 5175 2.74-0.03 Morel et al. in prep. 21
Red giants in NGC6633: individual frequencies By fitting the observed individual modes with Lorentz-like profile. Echelle diagrams l=0 l=1 l=2 22
Relative flux Radial Velocity (km/s) Red giants in NGC6633: RV data Search for solar-like oscillations in Radial Velocity data CoRoT Work in progress! 23
Conclusion 3 Red Giants with solar-like oscillations + spectroscopic data: - Atmospheric parameters - Seismic indices M,R - Indidividual frequencies Cluster membership test New contrains on the evolution and internal stucture Of Red giants RV + I data : new test on Convection treatment via mode amplitude 24
THE END! THANKS 25