The HR diagram stability enigmas and the asteroseismology of

The HR diagram stability enigmas and the asteroseismology of CoRoT targets Part II: Diffusion and radiative forces: problems and solutions Institut d’Astrophysique et de Géophysique de Liège Belgian Asteroseismology Group Part. I Diffusion effects in MS stars : overview Part. : Diffusion effects in MS stars : overview Diffusion effects : overview • In slowly rotating and/or strongly magnetic stars • Main effects : builds chemical composition gradients • Indirect effects : - on internal structure - on opacity - on convective regions - κ-mechanism - convection-related mechanism Part. II Modeling diffusion in A and B type stars Part II : Modeling diffusion in A and B type stars Modeling diffusion with CLES In stars with Teff > 6000 K Diffusion = grad (P, T, c) + radiative accelerations Development of C L E S (Code Liégeois d’Evolution Stellaire) Implementation of radiative accelerations Collaboration Georges Alecian (Meudon) Part II : Modeling diffusion in A and B type stars The Liege contribution • β Cephei – SPB stars : - Miglio, Bourge, Montalbán, Dupret, 2007, CoAst, to be published - Bourge, Théado, Thoul, 2007, CoAst, to be published • Rapidly oscillating Ap stars : - Théado, Dupret, Noels, 2007, in preparation - Théado, Vauclair, Cunha, 2005, A&A 443, 627 - Théado, Cunha, 2006, CoAst 147, 101 • Ae/Be Herbig stars : HD 104237 - Dupret, Théado, Böhm et al., 2007, CoAst, to be published Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Observational context β Ceph SPB - B0 - B3 - low order p and/or g modes - P = 1.6 – 8 h - B2 – B9 - High order g modes - P = 0.5 – 5 days , , , : CoRot Targets Excitation : κ-mechanism of iron at 2x105K Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Theoretical challenges - detection of β Cephei in low metallicity environments (Kolaczkowski et al. 2006) - unexplained excited modes in some β Cephei stars (Pamyathnyk et al. 2004, Ausseloos et al. 2004, Handler et 2005) al. - detection of hybrid SPB and β Cep pulsators (Handler et al. 2004, 2006, Jerzykiewicz et al. 2005, Chapellier et al. 2006, Balona et al. 2002) - detection of SPB type pulsations in cool B type stars (Antonello et al. 2006, Bruntt et al. 2006) Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Modeling diffusion effects Models with 2.5M < M < 12M Iron parametric profile = (Fe/Fe0) Référence : Miglio, Bourge, Montalbán and Dupret, 2007, CoAst Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Modeling diffusion effects Models with 2.5M < M < 12M Stability analysis Référence : Miglio, Bourge, Montalbán and Dupret, 2007, CoAst Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Modeling diffusion effects Models with 2.5M < M < 12M Stability analysis β Cephei SPB Référence : Miglio, Bourge, Montalbán and Dupret, 2007, CoAst Part II : Modeling diffusion in A and B type stars β Cephei and SPB Stars Modeling diffusion effects - enlargment of the theoretical instability strip - excitation of β Cephei pulsations in low Z environment - more excited modes (with lower periods) - enlargment of the overlap between SPB and β Cephei β Cephei SPB Référence : Miglio, Bourge, Montalbán and Dupret, 2007, CoAst Part II : Modeling diffusion in A and B type stars Rapidly oscillating Ap stars Observational context β Ceph SPB - B ≈ 102 to 103 G - abundance anomalies patches Bp -A p 35 roAp - P = 4-20 min (0.8 ≤ ν ≤ 4.2 mHz) - high order p modes - excitation : κ-mechanism of H δ Scuti γ Doradus Solar like Part II : Modeling diffusion in A and B type stars Rapidly oscillating Ap stars Theoretical challenges Standard models : excitation of low frequency modes (δ-Scuti) through the κ-mechanism of He • chemical peculiarities ? • excitation of high frequency modes (in H ionization region) ? • damping of low frequency modes (in HeII ionization region) ? non standard processes involved : - diffusion - magnetic field … Part II : Modeling diffusion in A and B type stars Rapidly oscillating Ap stars Modeling diffusion - H and He diffusion Théado, Vauclair and Cunha (2005, A&A) Théado & Cunha (2006, CoAst) roAp noAp M=1.8 M - Diffusion 1 1 1.8M 1.8M δ-Scuti modes Excited modes 2.0M 2.0M M=1.8M – model 2 3 3 2 2 1.6M 1.6M 5 5 4 4 H+ He++ 1 5 ν(mHz) Part II : Modeling diffusion in A and B type stars Rapidly oscillating Ap stars Modeling diffusion - H and He diffusion Théado, Vauclair and Cunha (2005, A&A) Théado & Cunha (2006, CoAst) roAp noAp Theoretical instability strip Part II : Modeling diffusion in A and B type stars Rapidly oscillating Ap stars Modeling diffusion - H and He diffusion - Heavy elements diffusion ? roAp noAp Théado, Vauclair and Cunha (2005, A&A) Théado & Cunha (2006, CoAst) In progress … Theoretical instability strip Part. III Diffusion in F and G type stars Part III : Diffusion in F and G type stars The Liege contribution Solar type stars : - Miglio, Montalbán, Maceroni, 2007, MNRAS 377, 373 - Théado, Vauclair, Charpinet et al., 2005, A&A 437, 553 - Miglio, Montalbán, 2005, A&A 441, 615 γ Doradus stars - Montalbán, Miglio, Théado, CoAst 2007, to be published Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? Diffusion = grad (P, T, c) = large time-scale - What are the effects of diffusion on solar type stars ? - Will this effects be detectable with COROT ? Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? • Pairs of models with similar M and external parameters Teff, L + + + ---- standard models ___ models with diffusion Référence : Théado et al. 2005, A&A 437, 560 Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? He++ He variation M=1.2M standard diffusion Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? He++ He variation standard diffusion zc boundary Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? He++ He variation l=0 l=1 l=2 standard diffusion Part III : Diffusion in F and G type stars Diffusion effects in solar type stars ? Probing diffusion effects with COROT ? • Envelope He abundance : ok - Basu, Mazumdar, Antia, Demarque (2004) - Verner, Chaplin, Elsworth (2006) : obs. > 84 days • Acoustic radius of the base of the convective envelope : ?? - Ballot, Turck-Chieze, Garcia (2004) : ok for 150 days - Verner, Chaplin, Elsworth (2006) : obs. > 182 days Conclusions on microscopic diffusion effects in slow rotators and magnetic stars κ-mechanism SPB β Ceph H gM - strong effects on excitation - improve agreement between models and observations Am n Bp -A p -F δ Scuti γ Doradus Solar like m Conclusions on microscopic diffusion effects in slow rotators and magnetic stars κ-mechanism SPB β Ceph H gM - strong effects on excitation - improve agreement between models and observations Am n Bp -A p convection-related mechanism -F m δ Scuti γ Doradus Solar like - Oscillation frequencies shift END