3D Radiation MHD Simulations of Massive Star Envelopes

Palomar Transient Factory, Theory Network Meeting - Palomar Observatory

Transcript

1. 3D Radiation MHD Simulations of Massive Star Envelopes Yan-Fei Jiang (ভᆱᷢ), Matteo Cantiello, Lars Bildsten, Eliot Quataert, Omer Blaes
2. The Eddington Luminosity Maeder et al. 2012
3. Massive Star Envelopes ! Massive stars can develop radiation dominated, loosely bound envelopes e.g Joss et al. 1973, Paxton et al. 2013 ! In 1D models such envelopes are characterized by: ! Superadiabatic Convection ! Density Inversions ! Gas Pressure Inversions ! Envelope Inflation (e.g. Sanyal et al. 2015)
4. Scientific Motivation Stability of Massive Stars, Massloss, LBV eruptions, SN Type, Compact Remnant
5. Stellar Radii, Massive Binary Evolution, BH-BH Binaries Progenitors… Scientific Motivation
6. Important questions ! Are the density inversions stable in 3D calculation of radiation dominated envelopes? ! How energy is transported in radiation dominated envelopes? ! Envelope Inflation? ! Potential coupling to mass-loss
7. Simulations Setup ATHENA with VET Radiation Module Jiang et al. 2015
8. The Opacity Jiang et al. 2015 At fixed density around Iron Opacity peak. Neighboring lines: x10 in rho Fe
9. Initial Conditions Guided from MESA 1D models StarTop StarDeep StarMid StarTop Mini= 80 Msun, R = 14 Rsun [Early Main Sequence] StarMid Mini= 80 Msun, R = 274 Rsun [H exhaustion] StarDeep Mini= 40 Msun, R = 431 Rsun [Hertzsprung Gap] Jiang et al. 2015
10. Different regimes in Radiation Dominated Convection Diff Rad Flux Advection Flux (“convection”…) Critical optical depth Optical depth where radiation diffusion timescale = dynamical timescale
11. Initial Conditions Guided from MESA 1D models StarTop StarDeep StarMid Jiang et al. 2015
12. STARDEEP The case with efficient convection StarDeep Mini= 40 Msun, R = 431 Rsun [Hertzsprung Gap] Jiang et al. 2015
13. STARDEEP The case with efficient convection StarDeep Mini= 40 Msun, R = 431 Rsun [Hertzsprung Gap] Jiang et al. 2015 Density Inversion is gone (volume averaged) (density weighted)
14. STARTOP The case with inefficient convection Jiang et al. 2015
15. STARTOP The case with inefficient convection Jiang et al. 2015
16. STARTOP The case with inefficient convection Jiang et al. 2015 Density Inversion still present (in average) Porosity reduces radiative acceleration, but not enough to make it sub-Eddington (volume averaged) (density weighted)
17. Hydro Summary Jiang et al. 2015
18. STARTOP Photosphere Tau = 1 R R
19. HYDRO Results 1. Static density inversions in super-Eddington envelopes are unstable 2. In slow diffusion, radiation dominated regime, advective radiation flux behaves like convection and agrees with MLT. Density inversions are unstable and washed out. 3. In rapid diffusion, radiation pressure dominated regime, the advective flux is unable to transport energy (convection is inefficient). Disagreement with MLT predictions 4. Porosity of density fluctuations reduce the effective radiation acceleration (but in some case not enough to become sub-Eddington. Density inversions can persist). 5. Radiation pressure dominated envelopes have time dependent oscillations
20. ENTER the B-FIELDS! (as it wasn’t complicated enough…) Magnetic fields might be ubiquitous in (massive) stars. In turbulent convection initially small amplitude magnetic fields can be amplified
21. ENTER the B-FIELDS! B1 B2 B3
22. Averaged Vertical Profile B3 B1 B2 StarTop (Hydro)
23. B3 B1 B2 StarTop (Hydro) Averaged Vertical Profile
24. Magnetic Buoyancy rho Vz Pb
25. Enhanced Density Fluctuation B3 B1 B2 StarTop (Hydro)
26. Compare with MLT 2…3
27. Increased Density Fluctuation with Magnetic Field StarTop (Hydro) B1 B2 B3
28. Energy Advection Velocity StarTop (Hydro) B1 B2 B3
29. Change of Density, Entropy Density Entropy B1 B2 B3
30. The Porosity Factor B1 B2 B3
31. MHD Results 1. With magnetic fields, convection is still inefficient in StarTop. 2.Convection amplifies turbulent magnetic fields 3.Buoyancy driven by the turbulent magnetic field enhances the advection flux compared with the predictions from MLT. 4.Magnetic field reduces the stellar radius, increases the density fluctuation and the porosity factor
32. Next ! Write up MHD results (in progress) ! Effect on Wind massloss (in progress) ! Global Simulations (in progress)
33. Backup Slides
34. Hydrostatic Equilibrium With Super-Eddington Flux Gas Pressure Inversions Onset of Convection What is the convective flux in the radiation dominated regime?
35. Averaged Vertical Profile Hydro B3
36. Star Top ATHENA + VET Radiation Module
37. Radiation MHD Simulations of Massive Stars Envelope Yan-Fei Jiangҁভᆱᷢ) Matteo Cantiello, Lars Bildsten, Eliot Quataert, Omer Blaes
38. Model Parameters The Opacity
39. The Critical Parameters
40. Magnetic Field in StarT op T opB3 T opB4 T opB7
41. Magnetic Field in StarT op Entropy in the strong magnetic field case
42. Simulation History
43. Averaged Vertical Profile Hydro T opB4 T opB3 T opB7
44. Averaged Vertical Profile Hydro T opB4 T opB3 T opB7
45. Averaged Vertical Profile Hydro T opB4 T opB3 T opB7
46. Averaged Vertical Profile Hydro T opB7
47. Magnetic Buoyancy rho Vz Pb
48. Enhanced Density Fluctuation Hydro T opB4 T opB3 T opB7
49. Summary •With magnetic field, the convection is still inefficient in StarT op. •Convection amplifies turbulent magnetic field •Buoyancy driven by the turbulent magnetic field enhances the advection flux compared with the predictions from ML T. •Magnetic field reduces the stellar radius, increases the density fluctuation and the porosity factor.
50. UnderStand Magnetic Buoyancy
51. Confirm Density Fluctuation is the Dominant Factor
52. Check The Equation T opB4 T opB3 T opB7
53. Compare with Alfven Velocity
54. Increased Density Fluctuation with Magnetic Field
55. Energy Advection Velocity
56. Change of Density, Entropy Density Entropy
57. The Porosity Factor
58. The Flux
59. The Kinetic and Magnetic Energy
60. Compare with ML T++
61. The Force Multiplier
62. The Force Multiplier