1 / 20

Rotation of KIC 11145123

Rotation of KIC 11145123. Takashi Sekii Division of Solar and Plasma Astrophysics and Hinode Science Center NAOJ. …in collaboration with Don Kurtz Hideyuki Saio Masao Takata Hiromoto Shibahashi & Simon Murphy Kurtz et al. (2014). The talk is about.

gareth-hayden
Download Presentation

Rotation of KIC 11145123

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Rotation of KIC 11145123 Takashi Sekii Division of Solar and Plasma Astrophysics and Hinode Science Center NAOJ

  2. …in collaboration with Don Kurtz Hideyuki Saio Masao Takata Hiromoto Shibahashi & Simon Murphy Kurtz et al. (2014)

  3. The talk is about • Asteroseismic inference on rotation of a terminal-age main-sequence star KIC11145123 • The star exhibits both p-mode oscillations and g-mode oscillations • The star is almost a rigid rotator • The envelope however is rotating slightly faster HELAS VI@Göttingen 4 Sep 2014

  4. KIC11145123 • A late A star • Kepler magnitude Kp=13 • Huber et al. (2014) • Effective temperature: Teff = 8050±200 K • Surface gravity: log g = 4.0±0.2 (g in cgs) HELAS VI@Göttingen 4 Sep 2014

  5. Oscillations of KIC11145123 • Kepler quarters 0-16, long cadence, 1340-day long Amplitude spectrum HELAS VI@Göttingen 4 Sep 2014

  6. Oscillations of KIC11145123 • Kepler quarters 0-16, long cadence, 1340-day long P-mode range G-mode range HELAS VI@Göttingen 4 Sep 2014

  7. Oscillations of KIC11145123 • It is a δ Sct-γ Dor hybrid • From the numerous peaks the following modes were selected for modelling • 5 p modes (1 singlet, 2 triplets & 2 quintuplets) • The singlet is of the highest amplitude • 15 g-mode triplets • High overtones with the mean period spacing ν1=17.964 d-1 ΔPg=0.0024 d HELAS VI@Göttingen 4 Sep 2014

  8. Modelling KIC 11145123 • The low value of ΔPg indicates that the star is in an advanced stage of evolution HELAS VI@Göttingen 4 Sep 2014

  9. Modelling KIC 11145123 • The strategy • Match ΔPg and then match ν1 • Then see how well the other modes fit HELAS VI@Göttingen 4 Sep 2014

  10. Modelling KIC 11145123 • The best model • M=1.46M • Has a convective core (r〜0.05R) • Z=0.01, Y=0.36 • Helium abandunce high • Too faint and too cool for the KIC parameters HELAS VI@Göttingen 4 Sep 2014

  11. Rotational shift of frequencies HELAS VI@Göttingen 4 Sep 2014

  12. Nearly a rigid rotator • The g-mode splittings show very small scattering • Δfg=0.0047562±0.0000023 d-1 (average) • Implies a rigid rate of about 0.0095 d-1 (in rotational frequency) • Cnl→1/2 for dipole g modes • The p-mode shifts are more or less consistent with this rate too • Cnl→0 for p modes • However… HELAS VI@Göttingen 4 Sep 2014

  13. Rotational shift of frequencies HELAS VI@Göttingen 4 Sep 2014

  14. Core vs envelope • The envelope seems to be rotating slightly faster since… • Δfg=0.0047562±0.0000023 d-1 (average) • Δfp=1.0101560±0.0000025 d-1 (l=1, n=3) • Δfp-2Δfg>0 • Note that • Ωp/2π＞Δfp (lower bound) • Ωg/2π<2Δfg (upper bound) HELAS VI@Göttingen 4 Sep 2014

  15. Two-zone modelling • Fitting the following form • …not even to individual splittings, but to the p- and g-averaged splittings HELAS VI@Göttingen 4 Sep 2014

  16. Two-zone modelling Solid: g-mode kernel Dotted: p-mode kernel Step functions: two-zone models Good separation between regions sampled by two kernels HELAS VI@Göttingen 4 Sep 2014

  17. Two-zone modelling • Averaging kernel (rb=0.3R) Solid: avg krn for Ω1 Dotted: avg krn for Ω2 ‘Localization’ fairly good and small dips do not affect the conclusion HELAS VI@Göttingen 4 Sep 2014

  18. Discussions (2/1) • The modelling uncertainty does worry us, but it does NOT affect the main inferences on the rotation • The nearly rigid rotation suggests a strong angular momentum transport • It is UNLIKELY that the star is strongly magnetic HELAS VI@Göttingen 4 Sep 2014

  19. Discussions (2/2) • If the envelope as a whole is rotating faster, why? • Angular transport by waves? A viscosity-type mechanism cannot spin the outside up over the internal rate • Mass accretion? • Also to explain the high He abandunce • One unexplored issue: what is the least exotic 2-d rotation profile consistent with data? HELAS VI@Göttingen 4 Sep 2014

  20. Summary • A terminal-age main-sequence A star KIC11145123 exhibit both p-mode oscillations and g-mode oscillations • This permits us to examine the core rotation and the envelope rotation separately • The star is almost a rigid rotator • The envelope however is rotating slightly faster ‘on average’ • There are implications on angular momentum transport mechanism HELAS VI@Göttingen 4 Sep 2014

More Related