Current open issues in probing interiors of solar-like oscillating main sequence stars

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Current open issues in probing interiors of solar-like oscillating main

sequence stars

MJ Goupil, Y. Lebreton Paris Observatory

J.P. Marques, R. Samadi, S. Talon ,J.Provost, S. Deheuvels, K. Belkacem, O. Benomar, F. Baudin, J. Ballot, B.Mosser T. Corbard, D. Reese, O. Creevey

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Outline

I The Sun Major open issues From the Sun to stars

II Solar like oscillating MS stars Open issues illustrated with CoRoT stars: HD49933, HD181420, HD42385 ground based observed HD208 Kepler data

Reviews: Basu, Antia 2008, Christensen-Dalsgaard, 2009; Turck Chieze et al , 2010

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A tout seigneur tout honneur, Noblesse oblige

The Sun

Solar constraints

• Luminosity, GM⊙, R, age, surface abundances (Z/X)s• Seismic constrainsFrom inversion of a large set of mode frequencies Found to be enough independent of the reference model

-base of the upper convective zone rbzc

-surface helium abundance Ys

-ionization regions through 1 -sound speed profile : seismic solar model c(r ) -rotation profile (r,)

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- Input parameters: surface abundances ?

- Interior : sound speed : origin of the discrepancy below the convection zone Rotation profile Near surface layers

- Probing the core

- Mode physics : line widths and amplitudes

convection-pulsation interaction-

Major challenges and open issues in the solar case

The Sun

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1993-2010: several revisions of the photospheric solar mixture2003: 3D model atmospheres + NLTE effects + improved atomic data➥ decrease of C, N, O, Ne, Ar and (Z/X)

GN93 GS98 AGS05 AGS09 Lod09 Caff10

Z/X 0.0245 0.0229 0.0165 0.0181 0.0191 0.0209

1- Initial abundances: the solar mixture

The Sun

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1993-2010: several revisions of the photospheric solar mixture2003: 3D model atmospheres + NLTE effects + improved atomic data➥ decrease of C, N, O, Ne, Ar and (Z/X)

Grevesse & Noels 93, Grevesse & Sauval 1998, Asplund et al. 05, Asplund & al 09, Lodders et al. 09, Caffau et al 10

GN93 GS98 AGS05 AGS09 Lod09 Caff10

Z/X 0.0245 0.0229 0.0165 0.0181 0.0191 0.0209

1- Initial abundances: the solar mixture

The Sun

2009-2010•Internal consistency of abundance determination from different ionisation levels of a given element •Consensus between independent determinations

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1 Initial abundances: the solar mixture

The Sun

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The Sun

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The Sun

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INPUT PHYSICS microscopic:Nuclear reactions opacities equation of state microscopic diffusion macroscopic: Convection rotation internal waves magnetic field et related transport

INPUT PARAMETERS mass initial composition evolutionary state

BOUNDARIES model atmospheres

NUMERICS

solar model

Mode physics

The sun

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1- Opacities: mixture and choice of tables

The Sun

Z/X decrease : major impact in solar models radiative opacities

Major differences just below the convection zone (Oxygen, Neon)

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1- Opacities: mixture and choice of tables

The Sun

Z/X decrease : major impact in solar models radiative opacities

Major differences just below the convection zone (Oxygen, Neon)

Check opacities: uncertainties assessed with OPAL/OP

Opacity comparison for a 1 Msun calibrated solar model

Difference in opacity dominated by the difference in the mixture (but less if AGS09 replaces AGS05).

OP opacities give a better fit than OPAL. However in that region, there is no way to change the OP opacity by a sufficient amount to compensate the effects of mixture (Badnell et al. 2005)

cf S. Basu ‘s talk S. Turck-Chieze ‘s talk

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1 Abundances

Abundances of other stars determined by reference to the

Sun, hence all stars affected can other stars be discriminating ?

Impact of some mismatch between 3D atmosphere models (solar abundances) and 1D models (stellar abundances)? Z/X could be affected

Impact of inconsistency when modelling other stars with AGS mixtures if their [Fe/H] not determined from 3D models?

From the Sun to stars

1414Yveline Lebreton GAIA-ELSA Conf., Sèvres, France, 10 June 2010

in stars: reactions occur at low energy: few keV to 0.1 MeV

rates from:•experimental data but to be extrapolated to low E•theory

reaction cross section:

2-Nuclear reaction rates The Sun

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recent significant progress in laboratory and theory➥ S-factor down to the Gamow peak

NOW and FUTURElow energy, high intensity underground

➦


reaction cross section:

astrophysical factor (S-factor)

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Adelberger et al. 2010

high mass or/and advanced stages

low mass stars

CNO cycle

pp chain

2-Hydrogen burning reaction rates

CNO cycle

S(0) ➘ 50%

LUNA

experimental measurements

14N(p, γ)15O

The Sun

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CNO cycle efficiency is reduced

Sun: ECNO/ETOT= 0.8% vs.1.6% before

2- 14N(p,γ)15O burning reaction rate

From the Sun to analogue starsconvective core: smaller at given mass , appears at higher mass

LUNA, Formicola et al. 04

NACRE, Angulo et al. 01convective coresmaller at given mass appears at higher mass

1.2 M☉, Z=0.01

The Sun

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)2exp()(

)( E

ESE

reaction cross section

Electron screening

Seismic sun (Basu et al 1997)- model

AGS05

Model S

Model Sswitching

off e-

screening

Christensen-Dalsgaard, 2009

Salpeter 1954Shaviv, Shaviv1996; 2000

Controversy Bahcall et al 2000Weiss et al 2001

Dappen 2009

Exact impact of e- screening ?For the Sun and stars ?


AGS09

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Adelberger et al. 2010

high mass or/and advanced stages

low mass stars

CNO cycle

pp chain

p(p, e+

ν)d

2-Hydrogen burning reaction rates

CNO cycle

The Sun

theoretical estimate onlybut helioseismic validation➦ rate constrained to ±15%

Weiss 2008pp+screening increase by 15% : AGS05 cs prior to 2003 standard solar modelsbelow th UCZ

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Open issues: flat rotation profile in the radiative region discrepancy for the sound speed below the UCZ

Most recent, based on a model of diffusion-advection transport (Zahn 1992, Maeder, Zahn 1998, Chaboyer, Zahn, 1992, Mathis, Zahn 2004)

Talon, Zahn 1997, high massMathias, Zahn, 1997 solar rotation profileTalon, Charbonnel 2003 Li dip

3- Rotationally induced transport The Sun

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Open issues: flat rotation profile in the radiative region discrepancy for the sound speed below the UCZ

Most recent, based on a model of diffusion-advection transport (Zahn 1992, Maeder, Zahn 1998, Chaboyer, Zahn, 1992, Mathis, Zahn 2004)

Talon, Zahn 1997, high massMathias, Zahn, 1997 solar rotation profileTalon, Charbonnel 2003 Li dip

Palacios et al 2006; Turck-Chieze et al 2010 :•Initial velocity (slow or ‘fast’ sun) matters•slow: microscopic diffusion dominates•Initially rapid enough: meridional circulation dominates over turbulent shear

3- Rotationally induced transport The Sun

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2

c

c

GN93 mixture

discrepancy for the sound speed below the UCZ increases

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The Sun3- Rotationally induced transport

Models from Marques 2010Lebreton 2010

AGS05• no rotation• rotation no surface J loss•rotation surface J loss

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From the Sun to stars: Talon, Zahn 1997, Eggenberger et al, Decressin et al 2009, Marques et al 2010

Validity of prescriptions, in particular Dh ?

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4-Internal wave induced transport

For profile, needs additional transport processes: waves mixing or BTalon, Charbonnel 2005 internal waves ⊙ flat profil Li dip on the cool side

B is also able to ⊙ flat profil Eggenberger et al 2005, Yang, Bi 2007 Open issue: either one ? or both ? depends on various precriptions and assumptions

The Sun

Sound speed

Evolution of sound speed profil with age Talon 2010 with 2005 models

(Talon, Charbonnel 2005) but not calibrated models yet For cs, needs higher opacities or higher helium below UZC ie higher He gradient Any mixing below UZC which smoothes the gradient goes in the wrong direction ? Then advection process? Waves ?

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Include

- boundary: T- relation

- Inefficient turbulent convection - Mode physics : nonadiabatic effects thermal and dynamics

interaction radiation-pulsation interaction convection-pulsation

5-Near surface layers The Sun

Christensen-Dalsgaard , Perez Hernandez 1992 Christensen-Dalsgaard, Thompson 1997

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5-Model atmosphere and T- law

Blue solar observations GOLF (credit F. Baudin)Red solar model GN93, diffusion (Lebreton 2010)

The Sun

From the Sun to stars, SSM uses semi empirical models or Kurucz modelsEvolutionary models for stars usually use Eddington T-

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Kjeldsen et al 2008 proposed a mean to correct for near surface effects

Green : corrected with a(obs/0)b

a,b fitted from the datareference frequency 0 = 3100 Hz fixed

Green fall on blue points

5-Correcting for near surface effects The Sun

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Of course valid only over the fitted domain,perhaps enough for stars

How much parameters a,b, 0 do depend on the adopted model ?

Validity for other stars ?

5-Correcting for near surface effects The Sun

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5-Correcting for near surface effects

Inefficient superadiabatic turbulent convection: 3D simulationsPatched model versus non patched models:Frequencies closer to observed ones Rosenthal et al 1999, Li et al 2002

Samadi, Ludwig 2010

The Sun

Existence of a similar scaling for that contribution to near surface effects ?Then it could be investigated theoretically

5-Correcting for near surface effectsFrom the Sun to stars

Hotter stars, larger effects

Pturb/Ptot larger, ‘lift’ of the atmosphere higher larger difference between patched and non patched model frequenciessmaller gravity and/orhigher température, larger Pturb/Ptot

curves : a(obs/max)b

with adapted a,b Scaling not so easy …

Models from Samadi, Ludwig 2010

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5-Correcting for near surface effectsFrom the Sun to stars

… but possible

Care with the ‘patching’3D simu not perfect

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StarsFrom the Sun to solar-like oscillating MS stars:

Stars can differ from the Sun by : Mass, age , Metallicity, Y Convective core Rotation …. Add additional issues:

Here focus on low and intermediate mass MS up to ~ 1.5 Msol (F,G,K stars)

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•Determining input parameters: mass, age, chemical composition Y0, (Z/X)0, , ov,usually through location in HR diagram and spectroscopic information as accurate as possible L, Teff, Z/X, R… but M, R, age , surface chemical composition not well known;


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• input parameters are needed: mass, age, chemical composition Y0, (Z/X)0, , ov,Most often M, R, age , surface chemical composition not well known;usually through location in HR diagram and spectroscopic information

These incertainties family of models rather than a unique one and input physics dependent desentangling degeneracy of these effects on seismic diagnostics


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• input parameters are needed: mass, age, chemical composition Y0, (Z/X)0, , ov,Most often M, R, age , surface chemical composition not well known;usually through location in HR diagram and spectroscopic information

These incertainties family of models rather than a unique one and input physics dependent desentangling degeneracy of these effects on seismic diagnostics •For a given star, seismic observations can lead to 2 scenarii for mode degree identifications


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Stars

•Additional seismic diagnostics and efforts in obtaining seismic constraints independent of models

Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010

Observational constraints:

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Stars



Sensitivity to convective core properties: period related to acoustic radius of core convective radius:Provost et al, 1993 Mazumdar, Antia 2001; Miglio et al 2005, Roxburgh, Vorontsov 2007…

d01


Deheuvels et al 2010

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Stars



Sensitivity to convective core properties: period related to acoustic radius of core convective radius:Provost et al, 1993 Mazumdar, Antia 2001; Miglio et al 2005, Roxburgh, Vorontsov 2001, 2005, Roxburgh 2005

Base of the UCZ, Ionization regionsMonteiro et al 2000; Mazumdar, Antia 2001; Mazumdar et al 2006; Roxburgh, Vorontsov 2003 ..

d01



38383838

Stars





Age, core properties, low degree modesHoudek, Gough 2007, 2008 ; Cunha, Metcalfe 2007; Cunha 2010

d01



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Stars





Age, core properties, low degree modesHoudek, Gough 2007, 2008 ; Cunha, Metcalfe 2007; Cunha 2010

•Enough observed stars enable to validate systematic properties: scalings relations Bedding, Kjeldsen 2010, Kjeldsen et al 2008

d01



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Initial abundances: the chemical mixture

Stars

Barban et al 2009 ; Baudin 2010, Ballot et al 2010; Benomar et al 2009

unevolved and ‘massive’: convective core , radiative interior, thin convective outer layer , rotation

Different metallicity

Evolved: isothermal core

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LUNA, Formicola et al. 04

NACRE, Angulo et al. 01

CNO cycle efficiency is reduced

14N(p,γ)15O burning reaction rate

convective coresmaller at given mass appears at higher mass

1.2 M☉, Z=0.01

Stars

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Stars Gravitational settling and atomic diffusion:Ys decreases

Effect increases with massDiffusion too large for small envelope convective region ?

Fe/H~0.08 M ~1.42-1.50ov=0.-0.2

Fe/H~0 M ~1.36-1.37ov=0-0.2

Fe/H~-0.44M=1.1-1.15ov ~0-0.2

Fe/H~ -0.07

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Sun

Fe/H~0.09 M ~1.30

Fe/H~-0.11

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1.1-1.2 Msol metal poorCompact with thin convective envelope

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Mode degree identification

• (CoRoT) HD49933 Initial run 30 days2 scenarii : A : need for large core overshoot B : need for intermediate core overshoot Appourchaux et al 2008Initial run + long run 137 days + several independent data analyses scenario B is favored Benomar et al 2009

•(CoRoT) HD1814202 scenarii : A : need for large core overshoot B : need for intermediate core overshoot Barban et al 2009and others

Stars

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Mode identification:scaling relations

Bedding, Kjeldsen 2010 proposed to use scaling relations to help identifie the modes: scaled echelle diagram

Reference star (CoRoT) HD49933 scenario B LR+IR ( Benomar et al 2009

•(CoRoT) HD181420 scenario 1 Barban et al 2009, Gaulme et al 2009, Mosser 2010

•(CoRoT) HD181906 scenario B Garcia et al 2009

scales as <> ; scales as <>

Test on ‘twin stars’: Sun and 18 Sco - Ceti and Cen B

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HD203608 Mosser et al, 2008; Deheuvels et al 2010Low mass F8V ~6070K; ~0.95 Msol, Fe/H ~-0.5Scenario A: clear evidence that definetly requires mild overshoot and survical of convective core despite its small mass, old age but due low metallicity

Ground based observations: 2 scenarii: arguments to choose scenario A but some check welcome

Scenario AStars

464646

HD203608 Mosser et al, 2008; Deheuvels et al 2010Low mass F8V ~6070K; ~0.95 Msol, Fe/H ~-0.5Scenario A: clear evidence that definetly requires mild overshoot and survical of convective core despite its small mass, old age but due low metallicity

Ground based observations: 2 scenarii: arguments to choose scenario A but some check welcome

Scenario A

Scenario B Scenario B

clearly confirms scenario A (Deheuvels, 2010, PhD)

Stars

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HD49933: a low metallicity low mass star

Initial run + long run 137 days - Scenario B [Fe/H]=-0.4 +/- 0.1 How well current models can reproduce the observations?

Can we find families of models satisfying all the obs. constraints?

Stars

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Stars

l=2 large error bars unreliable

Calibration: large separation and small spacing d01 large separation • Mean value <> : given M, Z/X, Y, physics / : fix the age•Period of oscillation: acoustic depth of He++ ionisation• phase of oscillation: sensitive to _cgm to Y quite constraining together with non seismic constraints

small spacing d01 sensitive to core conditions period = acoustic radius of convective core boundary

4949




Stars


AGS05: difficult to find a model satisfying all the constrains when Z/X is on the smaller part of the authorized interval



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HD49933Stars

Effects of its low metallicity:

AGS05 no diffusion

AGS05 diffusion needs to start with large Yini needs to include Dturb still small Ys value, (Z/X) Ys=0.10

Less extreme AGS09: Ys=0.18

•Diffusion and helium surface abundance

/<> versus /<>Scaling: oscillation phase independent of age

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HD49933: convective coreStars


GN93: convective core, sensitivity to core overshoot; need for intermediate to large core overshoot _ov = 0.25-0.3Hp

AGS05: small convective core , weak sensitivity to core overshootbut _ov cannot be zero

Diffusion : mild overshoot _ov=0.21Hp

•Diffusion

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AGS05

no diffusion ov=0.2 Hp: does not fit

Diffusion, ov=0.2 : fits

Diffusion+rotation ov=0.2 : fits

Diffusion+rotation no ov : does not fit

But requires proper calibration

•Diffusion and rotationally induced transportInitial angular rotation set to fit P=3.4 days at the age of HD49933

Models computed by J. Marques

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Echelle diagrams for HD49933Blue observationsRed model

86 HZ for both 86.5 HZ for model

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HD181420

Scenario 1 favors for intermediate core overshoot

Stars

( 6580K ; [Fe/H] ~0 or -0.12)

two models: 1.36 M with 0.2 Hp overshoot 1.37 M without overshootNo diffusion- No rotation

Secondary oscillation component in the large separation not reproduced by models.Its ‘period’ corresponds to the base of the convective zone but is it real ? Provost 2010, Goupil et al 2009, Michel, Mazumdar 2010, Mosser 2010

Data from Barban et al; Gaulme et al, Benomar et al

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l=0 l=1l=2

10km/s

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rotationa ‘rapid’ rotator compared to the Sun

With R=1.66 R☉ and split = (3.±1 ) Hz

Rotational velocity v = 21.9 ± 7.3 km/s

=2/(GM/R3) = 320 ⊙ !

HD181420Stars

5656

Effect of the non-spherically part of centrifugal distortion

on échelle diagram and asymetries of splitting multiplets (WarM oscillation code)

l=0 l=1l=2

10km/s

25 km/s

Asymetries of the splitting clearly appear in échelle diagram already at 10 km/sContribute to surface effects 27




=2/(GM/R3) = 320 ⊙ !

HD181420Stars

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rot = (4.5 ± 0.5) Hz (v sin i + R)

spot = (5.144 ± 0.068) Hz (Fourier)

split = (2.6 ± 0.4) Hz (scenario 1) (sismo)

indication of rapid rotation ; differential in latitude Ratio vspot/nurot gives a constraint on spot model

Effect of rotation is included only through effect of nonspherical centrifugal distorsion on the frequencies

1.36 model with overshoot: Rotation (vrot=2, 15, 20, 25, 30 km/s)included in computing the eigenfrequencies*decreases the mean value of d01.

The higher v, the lower d01

d01 indicates no oveshoot if vrot=20-25km/sor 0.2 Hp overshoot and vrot = 2 - 15 km/s

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• Coupling between the p-mode cavity and the g-mode cavity

=> low-degree avoided crossings are associated with a characteristic distortion of the ridge in the échelle diagram (Deheuvels & Michel 2009)

weak coupling strong coupling

• Case of HD 49385 : detection of an l=1 avoided crossing based on the distortion of the ridge.

HD49385: mixed mode and mixtureStars

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EZ

GN93 no overshooting

Models fitting all surface parameters + + frequency of the avoided croissing

We fit the distortion of the ridge(Deheuvels et al. 2010 in prep.)

Stars

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EZ


GN93 overshooting



Stars

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EZ


GN93 overshooting

ASP05 no overshooting



Stars

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Kepler data and scaling relations

Some degeneracy in determining mass and age or radiusdue to the chemical composition

Which accuracy in non seismic determination of Y,Z is needed ?

Corot targets, ground based observations4 Kepler targets provided by O. Creevey with permission of KASK group

Stars

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Conclusion

Et tout le reste…..

For exemple

Semi convection versus mixing for low mass starsStellar activityB

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Stars

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Stars




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Stars


AGS05: Difficult to find a model satisfying all the constrains when Z/X is on the smaller part of the authorized interval



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HD49933Stars


AGS05 no diffusion

AGS05 diffusion needs to start with large Yini needs to include Dturb still small Ys value, (Z/X) Ys=0.10

Less extreme AGS09: Ys=0.18

•Diffusion and helium surface abundance

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GN93: convective core, sensitivity to core overshoot; need for intermediate to large core overshoot _ov = 0.25-0.3Hp

AGS05: small convective core , weak sensitivity to core overshootbut _ov cannot be zero

Diffusion : mild overshoot _ov=0.21Hp

•Diffusion

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AGS05

no diffusion ov=0.2 Hp: does not fit

Diffusion, ov=0.2 : fits

Diffusion+rotation ov=0.2 : fits

Diffusion+rotation no ov : does not fit

But requires proper calibration

•Diffusion and rotationally induced transportInitial angular rotation set to fit P=3.4 days at the age of HD49933

Models computed by J. Marques

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HD181420

Scenario 1 favors for intermediate core overshoot

Stars

( 6580K ; [Fe/H] ~0 or -0.12)

two models: 1.36 M with 0.2 Hp overshoot 1.37 M without overshootNo diffusion- No rotation

Secondary oscillation component in the large separation not reproduced by models.Its ‘period’ corresponds to the base of the convective zone but is it real ? Provost 2010, Goupil et al 2009, Michel, Mazumdar 2010, Mosser 2010

Data from Barban et al; Gaulme et al, Benomar et al

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Effect of the non-spherically part of centrifugal distortion

on échelle diagram and asymetries of splitting multiplets (WarM oscillation code)

l=0 l=1l=2

10km/s

25 km/s

Asymetries of the splitting clearly appear in échelle diagram already at 10 km/sContribute to surface effects 27




=2/(GM/R3) = 320 ⊙ !

HD181420Stars

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rot = (4.5 ± 0.5) Hz (v sin i + R)

spot = (5.144 ± 0.068) Hz (Fourier)

split = (2.6 ± 0.4) Hz (scenario 1) (sismo)

indication of rapid rotation ; differential in latitude Ratio vspot/nurot gives a constraint on spot model

Effect of rotation is included only through effect of nonspherical centrifugal distorsion on the frequencies

1.36 model with overshoot: Rotation (vrot=2, 15, 20, 25, 30 km/s)included in computing the eigenfrequencies*decreases the mean value of d01.

The higher v, the lower d01

d01 indicates no oveshoot if vrot=20-25km/sor 0.2 Hp overshoot and vrot = 2 - 15 km/s

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• Coupling between the p-mode cavity and the g-mode cavity

=> low-degree avoided crossings are associated with a characteristic distortion of the ridge in the échelle diagram (Deheuvels & Michel 2009)

weak coupling strong coupling

• Case of HD 49385 : detection of an l=1 avoided crossing based on the distortion of the ridge.

HD49385: mixed mode and mixtureStars

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EZ




Stars

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EZ


GN93 overshooting



Stars

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EZ


GN93 overshooting

ASP05 no overshooting



Stars

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Kepler data and scaling relations

Some degeneracy in determining mass and age or radiusdue to the chemical composition

Which accuracy in non seismic determination of Y,Z is needed ?

Corot targets, ground based observations4 Kepler targets provided by O. Creevey with permission of KASK group

Stars

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Conclusion

Et tout le reste…..

For exemple

Semi convection versus mixing for low mass starsStellar activityB l=2, l=3 modesMode physics….

Current open issues in probing interiors of solar-like oscillating main sequence stars

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