MESA/GYRE & gravity-mode oscillations of massive stars

Transcription

1 MESA/GYRE & gravity-mode oscillations of massive stars MESA: thank you Bill Paxton GYRE: thank you Rich Townsend

2 MESA/GYRE & gravity-mode oscillations of massive stars Lecturer: Conny Aerts TAs: Timothy Van Reeth & Evan Bauer

3 Setting the scene Stellar evolution mainly tested from surface properties while life directed by stellar interior This MESA/GYRE class focuses on young stars with a well-developed convective core AIMS: probe physics in near-core regions from gravity- mode oscillations

4 Looking inside stars: quakes

5 The beauty of gravity modes Quakes = solution of perturbed SSE in terms of periodic eigenfunctions Oscillation modes described in terms of spherical harmonics: Depending on dominance of restoring force: 1. pressure modes (acoustic waves) 2. gravity modes (horizontal waves) Gravity waves propagate in the radiative zone,from surface to the near-core region

6 The beauty of gravity modes PhD Thesis Valentina Schmid Leuven, 2016 Green: l=0 Red: l=1, n=3 Blue: l=1, n=-20

7 MESA/GYRE computations of quakes Compute stellar models with MESA & their pulsations with

8 Topic 1: MESA predictions of gravity modes

9 Theoretical Predictions No rotation, no magnetic field, convective core, radiative envelope

10 Theoretical Predictions No rotation, no magnetic field, convective core, radiative envelope MESA

11 Minilab 1: compute the asymptotic period spacing for dipole g-modes of a massive star from ZAMS to TAMS

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16 Topic 2: GYRE predictions of gravity modes

17 A real B star: KIC Pápics et al. (2014): Teff=13000 K log g=4.1 vsini < 10 km/s M=3.25M

18 2 real F stars: KIC Schmid et al. (2015)

19 2 real F stars: KIC Schmid & Aerts (2016)

20 Minilab 2: compute the real period spacing for dipole zonal g-modes of a massive star from ZAMS to TAMS for n=-5,,-75; compare with the asymptotic value: how good is the latter? (How) does its quality change during evolution? P = Pn+1,l -Pn,l

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24 Mode trapping due to chemical composition gradient As pioneered by Miglio et al. (2008) prior to space data! M=6M, Xc=0.50 l=1 modes n=18,20,22 Xc=0.50 chemical composition gradient left behind by receding convective core

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26 Topic 3: turning on rotation in GYRE (not in MESA )

27 Effect of Rotation: tilt Rotation lifts frequency degeneracy:

28 Rotation & g-modes: TA rigid rotation Solve Laplace tidal equation, as function of spin parameter Convention in GYRE: m>0: prograde m<0: retrograde

29 An example: KIC Teff=7160 K, log g=4.13, vsini=28 km/s (Van Reeth et al. 2015)

30 Prograde & Retrograde Modes KIC : Teff=7070 K, log g=4.05, vsini=140 km/s (Van Reeth et al. 2015)

31 Apply TA to derive interior rotation Sample of 40 F-type g-mode pulsators (Van Reeth et al. 2016)

32 Minilab 3: compute GYRE frequencies of prograde dipole g-modes of massive stars in TA from ZAMS to TAMS for rigid rotation at 5,10,15,20% critical; compare with non-rotating case

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35 Topic 4: turning on mixing & core overshooting in MESA & rotation in GYRE

36 Effect of Chemical Gradient: Dips Van Reeth et al. (2015) Stars with shrinking core during# core-h burning: chemical gradient in near-core region

37 A real star:kic From Moravveji et al. (2015) Convective core overshooting fov or Dov Radial diffusive mixing in radiative envelope log Dmix (in cm^2/s)

38 Effect of Chemical Gradient: Dips KIC : Teff=7000 K, log g=3.97, vsini=68 km/s (Van Reeth et al. 2015)

39 A real star:kic Pápics et al. (2014)

40 Dips & chemical mixing Various types of mixing Mixing disconnected with rotation Rotationally induced mixing Schmid & Aerts (2016)

41 Dips & chemical mixing Various types of mixing in MESA Mixing disconnected with rotation Rotationally induced mixing log Dmix Schmid & Aerts (2016)

42 A real star:kic KIC : M=3.25M, Xc=0.50, frot=0.48/d, fov=0.024 Hp log Dmix=0.75±0.25 (Moravveji et al. 2016)

43 2 real F stars: KIC Maxilab: primary needs more complex mixing: rotational or other origin?

44 Maxilab: compute GYRE period spacings of prograde dipole gmodes of massive stars in TA from ZAMS to TAMS for rigid rotation at 5,10,15,20% critical and for diffusive mixing with D =10, 50,100 cm^2/s. Then repeat for different core overshooting values fov=0.010, 0.015, Plot the period spacing patterns. mix For the ultrafast or supermotivated: compare with data in Van Reeth et al. (2016)

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