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