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 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 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 Oscillations of KIC11145123 Kepler quarters 0-16, long cadence, 1340-day long des (g modes) metric data for m the surface e stars known veral hundred g its four-year first success, arise some baf adiabatic osd by the three er, the spheriAmplitude se indices repspectrum adial displacesurface nodes, gitude, respecradial, dipolar HELAS VI@Göttingen 4 Sep 2014 gative) m designates prograde (retrograde) modes with otation in the inertial frame. The radial order n is asth the structure in the radial direction (Takata 2012). arly follow Takata (2006) for the radial order of dipolar gative values of n denote the radial orders of g modes. Oscillations of KIC11145123 Kepler quarters 0-16, long cadence, 123 has a Kepler1340-day magnitude K p = 13, andlong is a late A RVATIONS AND FREQUENCY ANALYSIS the Kepler Input Catalogue (KIC) revised photometry l. 2014), its effective temperature is 8050 ± 200 K and gravity is log g = 4.0 ± 0.2 (cgs units), showing it to be uence A star. The data used for the analysis in this paper ler quarters 0 to 16 (Q0 – Q16) long cadence (LC) data. an orbital period about the Sun of 372.4536 d, hence are just over 93 d. We used the multi-scale, maximum (msMAP) pipeline data; information on the reduction n be found in the data release notes 211 . To optimise for exoplanet transit signals, the msMAP data pipeline trophysical signals with frequencies less than 0.1 d− 1 greater than 10 d). None of the pulsation frequencies in this paper are near to that lower limit, but if the star rotational signal, e.g. from starspots, that will have been he pipeline. Since, as we show, the rotation period is near y data reduction technique will struggle to find a direct s period because of its similarity to the time span or the Figure 1. Top panel: An amplitude spectrum for the Q0-16 Kepler long terly rolls.P-mode This has no range effect on our analysis. G-mode range cadence data up to the Nyquist frequency for KIC 11145123, showing the p panel of Fig. 1 shows a full amplitude spectrum out presence of both g modes and p modes that are clearly separated. The midist frequency for KIC 11145123 for the nearly continudle and bottom panels show expanded looks in the p-mode and g-mode HELAS 4 Sep 2014 Q0-16 LC data spanning 1340 d (3.7 y). There are pul- VI@Göttingen frequency ranges, respectively. oth the g-mode and p-mode frequency regions, which 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 ν1=17.964 d-1 15 g-mode triplets High overtones with the mean period spacing ΔPg=0.0024 d HELAS VI@Göttingen 4 Sep 2014 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 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 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 Rotational shift of frequencies dwnlm = m(1- Cnl ) ò Knl (r)W(r)dr HELAS VI@Göttingen 4 Sep 2014 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 Rotational shift of frequencies HELAS VI@Göttingen 4 Sep 2014 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 Two-zone modelling Fitting the following form ìï W 1 W(r) = í ïî W2 (0 £ r £ rb ) (rb £ r £ R) …not even to individual splittings, but to the p- and g-averaged splittings HELAS VI@Göttingen 4 Sep 2014 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 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 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 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 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