Nonradial Oscillations

The Science Case: Stellar Ages - directly for individual stars

Age determination is direct and reliable Ages to stars which are not accessible with cluster

method

1. Convection in Stars - direct probe of global & local parameters of envelope convection zones

Beyond MLT: constraining 3-D models

2. Other Fundamental Stellar Parameters: M, R, & Y

1. Y = He abundance and the dY/dZ relation2. Abundance patterns with depth, e.g. stellar pollution

Asteroseismology Today

The topology & dynamics of our Sun’sconvection zone:

Asteroseismology Today

B. Freytag & M. Steffen (2001)R. Stein & A. Nordlund (2003)

2-D model >

Strong up/down asymmetry

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Probing Interiors:

Asteroseismology Today

Pressure waves of different n & l : * large & small separations

Pressure waves of different l :

The Sun

Low order p-modes

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QuickTimeª and aGIF decompressor

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QuickTimeª and aGIF decompressor

are needed to see this picture.l=3, m=3

l=3, m=1l=3, m=2

1040 microHz

2020 microHz

83 microHz (200 min)

TheorySun

Angular order

Frequency

(in

creasi

ng r

adia

l ord

er)

Probing Interiors:

Asteroseismology Today

Pressure waves of different n & l :

* large separations:Proportional to inverse tdyn , hence to (GM / R3) 1/2.

* small separations:Proportional to r -1 and grad c2 , hence to stellar core and to molecular weight there: stellar age !

Bedding & Kjeldsen 2003

Sun’s p-modes:

Hydrogen abundance inside the present Sun:

Asteroseismology Today

JCD (2002)

Convection zonebottom visible >

First steps have been taken recently: Detections of individual p-modes in radial

velocity1. Alpha Cen A: a G-dwarf (Butler et al. 2004)2. Alpha Cen B: a K-dwarf (Bouchy & Carrier

2004)3. Eta Boo: a G subgiant maybe ? 4. Procyon: an F subgiant maybe ??5. Mu Arae: a G-dwarf (Bouchy et al 2006) (Neptune

planet was easier to discover !)

Other multi-mode pulsating stars1. Gamma Dor variables: g-modes2. Beta Cep & Delta Scuti variables3. white dwarfs

Asteroseismology Today

The First Comparison:

Asteroseismology Today

Kjeldsen et al (2005)

G2 V

G2 V

K1 V

1.10 Ms

1.00 Ms

0.93 Ms

1.23 Rs

1.00 Rs

0.87 Rs

n =

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

log L/L

¤

4.0 3.9 3.8 3.7

log Teff

Z=0.01

-8

-6

-4

-2

0

log M

cz/M¤

The 3-D topology of a moderately deepconvection zone:

So, what is going on ?

B. Freytag & M. Steffen (2001)R. Stein & A. Nordlund (2003)

2-D model >

Strong up/down asymmetry

QuickTimeª and aYUV420 codec decompressor

are needed to see this picture.

The 3-D topology of a shallowconvection zone:

So, what is going on ?

Freytag & Steffen (2001)P. Demarque et al (2004)

2-D model >

Stronger vorticity& coherence,more vigorous

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The excitation & damping of p-modesin a convection zone:

So, what could we learn ?

Robinson, Demarque et al (2003)

3-D models of 1.5 Sun-mass star >

Super-ad. overshoot

The 3-D topology of a shallowconvection zone can lead to:

So, what could we learn ?

QuickTimeª and aYUV420 codec decompressorare needed to see this picture.

Surface >

• non-gaussian eddy time-correlation > mode excitation R. Samadi et al. (2003)

• extended super-adiabatic layers > surface reflection P. Demarque et al. (2004)

• enhanced granulation R. Stein & A. Nordlund (2003)

 

© Thomas Kallinger

NGC 2264NGC 2264N

GC

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64

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10-1

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MOST 2004MOST 2004

15 Mon

V589 MonV588 Mon

MOST Field of View

Fabry target 15Mon (O-star)

Secondary targets V588Mon, V589Mon and 7 others

133166 frames 48.13 daysduty cycle ≈95%

 

© Thomas Kallinger

NGC 2264NGC 2264N

GC

22

64

NG

C 2

26

4

Scie

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eam

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pre

-MS

post

-MS

instability region

~3x10 5yr

~4x106yr

2 solar mass

Stellar evolutionStellar evolution

R » »

P

Q P