Characteristics of Oscillations in G-type Giants

- Convection Zone in giants -

安藤裕康 (Ando Hiroyasu)坪井優介 (Tsuboi Yusuke)

神戸栄治 (Kambe Eiji)佐藤文衛 (Sato Bun’ei)

　2009 年 10 月 7 日

Objective

Internal Structure viaOscillations

Helioseismology and AsteroseismologyEx. Sun, α Cen A,B, 70 OphExtend to Sub-giants and giants

Excitation MechanismConvective motion still actives in giants ?

dwarfs

subgiants

giants

Present status of oscillations in giants

Propose observation of oscillations in G-type giants

ξ Hya and ε Oph

Characteristics of oscillations

Echelle diagram for frequencySolar 5 min. oscillations

even odd

Scaling laws

αCen A at VLT and AAT

(Butler et al. 2004)

Stellar parametersfor

Observational objects （ G-type giants ）　　　　

Stars with extra-solar planet

Some relation between planet-hosting and oscillation ?

ζ Hya

η Her

ε Tau

11 Com

ζ Hya

11 Com

ε Tau

η Her

Log g

2.30

2.51

2.57

2.79

ζ Hya 　

η Her

ε Tau

11 Com

Summary of observations

Parameters for Solar-like oscillation stars

Scaling law for νmax

Scaling law △ν

Damping time

1 　（ ν max, ν) follows scaling law△

2 echelle diagram of mode frequencies　　　＝＞　 detect not only radial oscillations, but also non- radial oscillations

３　 Damping time is around 2 days　　　（ not all eigen modes is excited simultaneously ）

４　 Detected oscillations are solar-like oscillations

5 Oscillations have no correlation with planet-hovering stars

Summary of characteristics of Oscillations in G giants

One unexpected results

ZAMS stage

P-region and G-region separated

Subgiant stage

Weak resonance

P

G

Giant stage

Strong resonance Amplitude reduced at surface

If convective zone is deeper,P-region and G-region separated

G P

Non-radial modes easily detectable

To expain the observation,

One possibility is that surface convection zoneis deeper than predicted by current convective theory

Thank you