Download Stars

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
1
Outline
I The Sun
Reviews: Basu, Antia 2008, Christensen-Dalsgaard, 2009; Turck Chieze et al , 2010
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
2
A tout seigneur tout honneur, Noblesse oblige
The Sun
Solar constraints
•
Luminosity, GM⊙, R, age, surface abundances (Z/X)s
• Seismic constrains
From inversion of a large set of mode frequencies
Found to be enough independent of the reference model
-base of the upper convective zone
-surface helium abundance
-ionization regions through
-sound speed profile : seismic solar model
-rotation profile
rbzc
Ys
1
c(r )
(r,)
3
The Sun
Major challenges and open issues in the solar case
- 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
4
The Sun
1- Initial abundances: the solar mixture
1993-2010: several revisions of the photospheric solar mixture
2003: 3D model atmospheres + NLTE effects + improved atomic data
➥ decrease of C, N, O, Ne, Ar and (Z/X)
Z/X
GN93
GS98
AGS05
AGS09
Lod09
Caff10
0.0245
0.0229
0.0165
0.0181
0.0191
0.0209
5
The Sun
1- Initial abundances: the solar mixture
1993-2010: several revisions of the photospheric solar mixture
2003: 3D model atmospheres + NLTE effects + improved atomic data
➥ decrease of C, N, O, Ne, Ar and (Z/X)
Z/X
GN93
GS98
AGS05
AGS09
Lod09
Caff10
0.0245
0.0229
0.0165
0.0181
0.0191
0.0209
2009-2010
•Internal consistency of abundance determination
from different ionisation levels of a given element
•Consensus between independent determinations
Grevesse & Noels 93, Grevesse & Sauval 1998, Asplund et al. 05, Asplund & al 09, Lodders et al. 09, Caffau et al 10
6
The Sun
1 Initial abundances: the solar mixture
7
The Sun
1 Initial abundances: the solar mixture
8
The Sun
1 Initial abundances: the solar mixture
9
The sun
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
solar model
Mode physics
NUMERICS
10
The Sun
1- Opacities: mixture and choice of tables
Z/X decrease : major impact in solar models  radiative opacities
Major differences just below the convection zone (Oxygen, Neon)
11
The Sun
1- Opacities: mixture and choice of tables
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
12
From the Sun to stars
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?
13
The Sun
2-Nuclear reaction rates
reaction cross section:
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
Yveline Lebreton
GAIA-ELSA Conf., Sèvres, France, 10 June
2010
14
The Sun
2-Nuclear reaction rates
recent significant progress in laboratory and theory
➥ S-factor down to the Gamow peak
NOW and FUTURE
low energy, high
underground
intensity
reaction cross section:
➦
astrophysical factor (S-factor)
15
The Sun
2-Hydrogen burning reaction rates
CNO cycle
high mass
or/and advanced stages
CNO cycle
pp chain
14N(p,
γ)15O
experimental
measurements
LUNA
low mass stars
S(0) ➘ 50%
Adelberger et al. 2010
16
The Sun
2-
14N(p,γ)15O
burning reaction rate
CNO cycle efficiency is reduced
Sun: ECNO/ETOT= 0.8% vs.1.6% before
From the Sun to analogue stars
convective core: smaller at given mass , appears at higher mass
convective core
smaller at given mass
appears at higher mass
NACRE, Angulo et al. 01
LUNA, Formicola et al. 04
1.2 M☉, Z=0.01
17
The Sun
2-Nuclear reaction rates
reaction cross section
S (E)
 (E) 
exp( 2)
E
Seismic sun (Basu et al 1997)- model
Electron screening
Salpeter 1954
Shaviv, Shaviv1996; 2000
Controversy Bahcall et al 2000
Weiss et al 2001
Dappen 2009
AGS09
AGS05
Model S
switching off
e- screening
Model S
Exact impact of e- screening ?
18
For the Sun and stars ?
Christensen-Dalsgaard, 2009
The Sun
2-Hydrogen burning reaction rates
CNO cycle
high mass
or/and advanced stages
CNO cycle
theoretical estimate only
but helioseismic validation
➦ rate constrained to ±15%
pp chain
low mass stars
Adelberger et al. 2010
p(p, e+ ν)d
Weiss 2008
pp+screening increase by 15% :
AGS05 cs  prior to 2003 standard solar models
below th UCZ
19
The Sun
3- Rotationally induced transport
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 mass
Mathias, Zahn, 1997 solar rotation profile
Talon, Charbonnel 2003 Li dip
20
The Sun
3- Rotationally induced transport
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 mass
Mathias, Zahn, 1997 solar rotation profile
Talon, 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
c 2
c2
GN93 mixture
discrepancy for the sound speed below the UCZ increases
21
The Sun
3- Rotationally induced transport
AGS05
• no rotation
• rotation no surface J loss
•rotation surface J loss
Validity of prescriptions,
in particular Dh ?
Models from Marques 2010
Lebreton 2010
From the Sun to stars: Talon, Zahn 1997, Eggenberger et al,
Decressin et al 2009, Marques et al 2010
22
22
The Sun
4-Internal wave induced transport
For  profile, needs additional transport processes: waves mixing or B
Talon, 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
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 ?
23
The Sun
5-Near surface layers
Include
- boundary: T- relation
- Inefficient turbulent convection
- Mode physics : nonadiabatic effects
thermal and dynamics
interaction radiation-pulsation
interaction convection-pulsation
Christensen-Dalsgaard , Perez Hernandez 1992
Christensen-Dalsgaard, Thompson 1997
24
The Sun
5-Model atmosphere and T- law
Blue solar observations GOLF (credit F. Baudin)
Red solar model GN93, diffusion (Lebreton 2010)
From the Sun to stars, SSM uses semi empirical models or Kurucz models
Evolutionary models for stars usually use Eddington T-
25
The Sun
5-Correcting for near surface effects
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 data
reference frequency
0 = 3100 Hz fixed
Green fall on blue points
26
The Sun
5-Correcting for near surface effects
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 ?
27
The Sun
5-Correcting for near surface effects
Inefficient superadiabatic turbulent convection: 3D simulations
Patched model versus non patched models:
Frequencies closer to observed ones
Rosenthal et al 1999, Li et al 2002
Samadi, Ludwig 2010
Existence of a similar scaling for that
contribution to near surface effects ?
Then it could be investigated theoretically
28
From the Sun
to stars
5-Correcting for near surface effects
Hotter stars, larger effects
Pturb/Ptot larger, ‘lift’ of the
atmosphere higher
larger difference between
patched and non patched
model frequencies
smaller gravity and/or
higher température,
larger Pturb/Ptot
Models from Samadi, Ludwig 2010
curves : a(obs/max)b
with adapted a,b
Scaling not so easy
…
From the Sun
to stars
5-Correcting for near surface effects
… but possible
Care with the ‘patching’
3D simu not perfect
30
Stars
From the Sun to solar-like oscillating MS stars:
Here focus on low and intermediate mass MS up to ~ 1.5 Msol
(F,G,K stars)
Stars can differ from the Sun by :
Mass, age , Metallicity, Y
Convective core
Rotation
….
 Add additional issues:
31
Stars
From the Sun to solar-like oscillating MS stars:
Here focus on low and intermediate mass MS up to ~ 1.5 Msol
(F,G,K stars)
Stars can differ from the Sun by :
Mass, age , Metallicity, Y
Convective core
Rotation
….
 Add additional issues:
•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;
32
Stars
From the Sun to solar-like oscillating MS stars:
Here focus on low and intermediate mass MS up to ~ 1.5 Msol
(F,G,K stars)
Stars can differ from the Sun by :
Mass, age , Metallicity, Y
Convective core
Rotation
….
 Add additional issues:
• 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
33
Stars
From the Sun to solar-like oscillating MS stars:
Here focus on low and intermediate mass MS up to ~ 1.5 Msol
(F,G,K stars)
Stars can differ from the Sun by :
Mass, age , Metallicity, Y
Convective core
Rotation
….
 Add additional issues:
• 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
34
Stars
Observational constraints:
•Additional seismic diagnostics and efforts in obtaining seismic constraints
independent of models
Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010
35
Stars
Observational constraints:
•Additional seismic diagnostics and efforts in obtaining seismic constraints
independent of models
Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010
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
36
Stars
Observational constraints:
•Additional seismic diagnostics and efforts in obtaining seismic constraints
independent of models
Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010
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 regions
d01
Monteiro et al 2000; Mazumdar, Antia 2001;
Mazumdar et al 2006; Roxburgh, Vorontsov 2003 ..
Deheuvels et al 2010
37
Stars
Observational constraints:
•Additional seismic diagnostics and efforts in obtaining seismic constraints
independent of models
Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010
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…
Base of the UCZ, Ionization regions
d01
Monteiro et al 2000; Mazumdar, Antia 2001;
Mazumdar et al 2006; Roxburgh, Vorontsov 2003 ..
Age, core properties, low degree modes
Houdek, Gough 2007, 2008 ; Cunha, Metcalfe 2007;
Cunha 2010
Deheuvels et al 2010
38
Stars
Observational constraints:
•Additional seismic diagnostics and efforts in obtaining seismic constraints
independent of models
Mean large separation: Mosser Appourchaux, 2009, Roxburgh 2009, Mathur et al 2010
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
Base of the UCZ, Ionization regions
Monteiro et al 2000; Mazumdar, Antia 2001;
Mazumdar et al 2006; Roxburgh, Vorontsov 2003 ..
Age, core properties, low degree modes
Houdek, Gough 2007, 2008 ; Cunha, Metcalfe 2007;
Cunha 2010
•Enough observed stars enable to
relations
Deheuvels et al 2010
validate systematic properties: scalings
Bedding, Kjeldsen 2010, Kjeldsen et al 2008
39
Stars
Initial abundances: the chemical mixture
Evolved: isothermal core
unevolved and ‘massive’:
convective core ,
radiative interior,
thin convective outer layer ,
rotation
Different metallicity
40
Barban et al 2009 ; Baudin 2010, Ballot et al 2010; Benomar et al 2009
Stars
14N(p,γ)15O
burning reaction rate
CNO cycle efficiency is reduced
convective core
smaller at given mass
appears at higher mass
NACRE, Angulo et al. 01
LUNA, Formicola et al. 04
1.2 M☉, Z=0.01
41
Stars
Gravitational settling and atomic diffusion:
Ys decreases
Effect increases with mass
Diffusion too large for small envelope convective region ?
Fe/H~0.08
M ~1.42-1.50
ov=0.-0.2
Fe/H~0.09
M ~1.30
Fe/H~0
M ~1.36-1.37
ov=0-0.2
Fe/H~-0.11
Fe/H~-0.44
M=1.1-1.15
ov ~0-0.2
1.1-1.2 Msol metal poor
Compact with thin convective envelope
Sun
Fe/H~ -0.07
6
42
42
Stars
Mode degree identification
• (CoRoT) HD49933 Initial run 30 days
2 scenarii : A : need for large core overshoot
B : need for intermediate core overshoot
Appourchaux et al 2008
Initial run + long run 137 days + several independent data analyses
scenario B is favored Benomar et al 2009
•(CoRoT) HD181420
2 scenarii : A : need for large core overshoot
B : need for intermediate core overshoot
Barban et al 2009
and others
43
Mode identification:scaling relations
Bedding, Kjeldsen 2010 proposed to use scaling relations to help
identifie the modes: scaled echelle diagram
 scales as < > ;  scales as < >
Test on ‘twin stars’: Sun and 18 Sco -  Ceti and  Cen B
Reference star (CoRoT) HD49933 scenario B LR+IR ( Benomar et al 2009
•(CoRoT) HD181420 scenario 1
•(CoRoT) HD181906 scenario B
Barban et al 2009, Gaulme et al 2009, Mosser 2010
Garcia et al 2009
44
Stars
HD203608
Scenario A
Mosser et al, 2008; Deheuvels et al 2010
Low mass F8V ~6070K; ~0.95 Msol, Fe/H ~-0.5
Scenario 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
45
Stars
HD203608
Scenario A
Mosser et al, 2008; Deheuvels et al 2010
Low mass F8V ~6070K; ~0.95 Msol, Fe/H ~-0.5
Scenario 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 B
clearly confirms scenario A
Scenario B
(Deheuvels, 2010, PhD)
46
Stars
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?
47
Stars
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?
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
48
Stars
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?
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
AGS05: difficult to find a model satisfying all the constrains
when Z/X is on the smaller part of the authorized interval
49
Stars
HD49933
•Diffusion and helium surface abundance
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
Scaling:
 /< >
versus /< >
oscillation phase independent of age
50
Stars
HD49933: convective core
•Diffusion
Effects of its low metallicity:
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 overshoot
but _ov cannot be zero
Diffusion : mild overshoot _ov=0.21Hp
51
Stars
HD49933: convective core
•Diffusion and rotationally induced transport
Initial angular rotation set to fit P=3.4 days at the age of HD49933
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
Models computed by J. Marques
52
Echelle diagrams for HD49933
86 HZ for both
Blue observations
Red model
86.5 HZ for model
53
Stars
HD181420
( 6580K ; [Fe/H] ~0 or -0.12)
Scenario 1 favors for intermediate core overshoot
two models: 1.36 M with 0.2 Hp overshoot
1.37 M
without overshoot
No 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 54
et al
Stars
HD181420
rotation
a ‘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
l=2
⊙
l=0
!
l=1
10km/s
27
55
Stars
HD181420
rotation
a ‘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
l=2
⊙
Effect of the non-spherically part of centrifugal distortion
on échelle diagram and asymetries of splitting multiplets
(WarM oscillation code)
!
l=0
l=1
10km/s
25 km/s
Asymetries of the splitting clearly appear in échelle diagram already at 10 km/s
Contribute to surface effects
27
56
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.
Effect of rotation is included only through effect of
nonspherical centrifugal distorsion on the
frequencies
The higher v, the lower d01
d01 indicates
no oveshoot if vrot=20-25km/s
or
0.2 Hp overshoot and vrot = 2 - 15 km/s
rot
= (4.5 ± 0.5)
Hz
spot = (5.144 ± 0.068) Hz
split
=
(2.6 ± 0.4)
Hz (scenario 1)
(v sin i + R)
(Fourier)
(sismo)
indication of rapid rotation ; differential in latitude
Ratio vspot/nurot gives a constraint on spot model
25
57
Stars
HD49385: mixed mode and mixture
•
Coupling between the pmode cavity and the gmode cavity
weak coupling
strong coupling
=> low-degree avoided
crossings are associated
with a characteristic
distortion of the ridge in
the échelle diagram
(Deheuvels & Michel 2009)
•
Case of HD 49385 : detection of an l=1 avoided crossing
based on the distortion of the ridge.
58
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
59
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
GN93 overshooting
60
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
GN93 overshooting
ASP05 no overshooting
61
Stars
Kepler data and scaling relations
Corot targets, ground based observations
4 Kepler targets provided by O. Creevey with permission of KASK group
Some degeneracy in determining mass and age or radius
due to the chemical composition
Which accuracy in non seismic determination of Y,Z is needed ?
62
Conclusion
Et tout le reste…..
For exemple
Semi convection versus mixing for low mass stars
Stellar activity
B
63
64
65
66
Stars
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?
67
Stars
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?
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
68
Stars
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?
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
AGS05: Difficult to find a model satisfying all the constrains
when Z/X is on the smaller part of the authorized interval
69
Stars
HD49933
•Diffusion and helium surface abundance
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
70
Stars
HD49933: convective core
•Diffusion
Effects of its low metallicity:
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 overshoot
but _ov cannot be zero
Diffusion : mild overshoot _ov=0.21Hp
71
Stars
HD49933: convective core
•Diffusion and rotationally induced transport
Initial angular rotation set to fit P=3.4 days at the age of HD49933
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
Models computed by J. Marques
72
Stars
HD181420
( 6580K ; [Fe/H] ~0 or -0.12)
Scenario 1 favors for intermediate core overshoot
two models: 1.36 M with 0.2 Hp overshoot
1.37 M
without overshoot
No 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 73
et al
Stars
HD181420
rotation
a ‘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
l=2
⊙
Effect of the non-spherically part of centrifugal distortion
on échelle diagram and asymetries of splitting multiplets
(WarM oscillation code)
!
l=0
l=1
10km/s
25 km/s
Asymetries of the splitting clearly appear in échelle diagram already at 10 km/s
Contribute to surface effects
27
74
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.
Effect of rotation is included only through effect of
nonspherical centrifugal distorsion on the
frequencies
The higher v, the lower d01
d01 indicates
no oveshoot if vrot=20-25km/s
or
0.2 Hp overshoot and vrot = 2 - 15 km/s
rot
= (4.5 ± 0.5)
Hz
spot = (5.144 ± 0.068) Hz
split
=
(2.6 ± 0.4)
Hz (scenario 1)
(v sin i + R)
(Fourier)
(sismo)
indication of rapid rotation ; differential in latitude
Ratio vspot/nurot gives a constraint on spot model
25
75
Stars
HD49385: mixed mode and mixture
•
Coupling between the pmode cavity and the gmode cavity
weak coupling
strong coupling
=> low-degree avoided
crossings are associated
with a characteristic
distortion of the ridge in
the échelle diagram
(Deheuvels & Michel 2009)
•
Case of HD 49385 : detection of an l=1 avoided crossing
based on the distortion of the ridge.
76
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
77
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
GN93 overshooting
78
Stars
Models fitting all surface
parameters +
+ frequency
of the avoided croissing
We fit the distortion of the ridge
EZ
(Deheuvels et al. 2010 in prep.)
GN93 no overshooting
GN93 overshooting
ASP05 no overshooting
79
Stars
Kepler data and scaling relations
Corot targets, ground based observations
4 Kepler targets provided by O. Creevey with permission of KASK group
Some degeneracy in determining mass and age or radius
due to the chemical composition
Which accuracy in non seismic determination of Y,Z is needed ?
80
Conclusion
Et tout le reste…..
For exemple
Semi convection versus mixing for low mass stars
Stellar activity
B
l=2, l=3 modes
Mode physics
….
81
82