surface abundances of am stars as a constraint on rotational mixing olivier richard 1,2, suzanne...
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![Page 1: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/1.jpg)
Surface abundances of Am Surface abundances of Am stars stars
as a constraint on rotational as a constraint on rotational mixingmixing
Olivier Richard1,2, Suzanne Talon2, Georges Michaud2
1 GRAAL UMR5024, Université Montpellier II, Montpellier, France
2 Département de physique, Université de Montréal, Montréal, Canada
![Page 2: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/2.jpg)
• Am stars
• Montréal Models
• Results
Surface abundances of Am Surface abundances of Am stars stars
as a constraint on rotational as a constraint on rotational mixingmixing
![Page 3: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/3.jpg)
• Statistics suggest all non-magnetic stars with V<80 km/s• Recent observations in open clusters
Mg~ normal Al, Si, S: ~normal or slight overabundance Ca ~ normal or underabundant Ni and Fe overabundant
Am StarsAm Stars
![Page 4: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/4.jpg)
Burger’s equationsBurger’s equations
• 2 equations for each species (28 in the code)• Solved for each mesh points (~1500)• and at each time step (~1000)
5 5
2 2
j i i jii i i i
j i j
ji ij i
ij ij
ijij ij j
j i
j
r di
j i
a
ij
m r m rPm N g N Z eE
r m m
mTN k a r b
w wg
rr m m
K
w
z
zK w
![Page 5: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/5.jpg)
Radiative accelerationsRadiative accelerations
• 1.5 GigaBytes of data ; OPAL (1996)– Integration over
fraction of photons given to i at each frequency
2 0
1 ( )
(to( ) )
l)(
t4 a
ru
adr
ia
Rr
ud
LP u d
ig u
r c Xi
Expression used in evolution calculations
hu
kT
4
24
15( )
4 1
u
u
u eP u
e
( )u i
(total)u
(Fe)u
(Li)u
![Page 6: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/6.jpg)
Mixing modelMixing model
• Simplest version of the turbulent diffusion coefficient obtained from self-consistent treatment of the meridional circulation following Zahn (1992)
• Mixing added to the code as a diffusion process with a parametric mixing diffusion coefficient:
TnD
![Page 7: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/7.jpg)
Mixing modelMixing model
• Simplest version of the turbulent diffusion coefficient obtained from self-consistent treatment of the meridional circulation following Zahn (1992)
• Mixing added to the code as a diffusion process with a parametric mixing diffusion coefficient:
TnD
![Page 8: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/8.jpg)
Computed modelsComputed models
• Models of 1.7 and 1.9 solar masses
• With mixing coefficient corresponding to surface velocity of 50 km/s (V50), 15 km/s (V15), and 5 km/s (V5, V5N)
Richer et al. (2000) 1.9R300-2 and 1.9R1k-2 models
![Page 9: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/9.jpg)
Effective temperature and surface gravity evolution
1.9
1.7
![Page 10: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/10.jpg)
Radiative acceleration in the 1.9 solar masses models
![Page 11: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/11.jpg)
Abundance profiles at 800 Myr
Model 1.9V5
r
1
0
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Abundance evolution in the 1.9 solar masses models
![Page 13: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/13.jpg)
The Praesepe star HD73045
![Page 14: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/14.jpg)
The Praesepe star HD73045
![Page 15: Surface abundances of Am stars as a constraint on rotational mixing Olivier Richard 1,2, Suzanne Talon 2, Georges Michaud 2 1 GRAAL UMR5024, Université](https://reader031.vdocuments.site/reader031/viewer/2022012918/56649ee15503460f94bf21ff/html5/thumbnails/15.jpg)
Conclusion
• In the mixing model the turbulence seems to be too strong to allow the Am phenomenon to occur at a reasonable velocity
• Need of self-consistent abundance determination for a lot of chemical species in stars of different ages and metallicity