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 relation 2. Abundance patterns with depth, e.g. stellar pollution Asteroseismology Today

The topology & dynamics of our Sun’s convection zone: Asteroseismology Today B. Freytag & M. Steffen (2001) R. Stein & A. Nordlund (2003) 2-D model > Strong up/down asymmetry

Probing Interiors: Asteroseismology Today Pressure waves of different n & l : * large & small separations Pressure waves of different l : The Sun

Low order p-modes l=3, m=3 l=3, m=1l=3, m=2

1040 microHz

2020 microHz

83 microHz (200 min)

Theory Sun Angular order Frequency (increasing radial order)

Probing Interiors: Asteroseismology Today Pressure waves of different n & l : * large separations: Proportional to inverse t dyn, hence to (GM / R 3 ) 1/2. * small separations: Proportional to r -1 and grad c 2, 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 zone bottom visible >

First steps have been taken recently:  Detections of individual p-modes in radial velocity 1. 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 stars 1. Gamma Dor variables: g-modes 2. Beta Cep & Delta Scuti variables 3. white dwarfs Asteroseismology Today

The First Comparison: Asteroseismology Today Kjeldsen et al (2005) G2 V K1 V 1.10 M s 1.00 M s 0.93 M s 1.23 R s 1.00 R s 0.87 R s n =

The 3-D topology of a moderately deep convection zone: So, what is going on ? B. Freytag & M. Steffen (2001) R. Stein & A. Nordlund (2003) 2-D model > Strong up/down asymmetry

The 3-D topology of a shallow convection zone: So, what is going on ? Freytag & Steffen (2001) P. Demarque et al (2004) 2-D model > Stronger vorticity & coherence, more vigorous

The excitation & damping of p-modes in 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 shallow convection zone can lead to: So, what could we learn ? 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 2264 Science Team Meeting Dec 2005 MOST Mon V589 Mon V588 Mon MOST Field of View Fabry target 15Mon (O-star) Secondary targets V588Mon, V589Mon and 7 others frames days duty cycle ≈95%

© Thomas Kallinger NGC 2264 Science Team Meeting Dec 2005 pre-MS post-MS instability region ~3x10 5 yr ~4x10 6 yr 2 solar mass Stellar evolution R »  » P