1. Physics of Supernovae Konstantin Postnov, Sternberg Astronomical Institute, Moscow, Russia Erice 2004, July 3

2. Outlook Introduction Core collapse supernovae (SN II, Ib, Ic). Asymmetry: magnetorotational explosion Thermonuclear supernovae (SN Ia). SN Ia light curve modeling Conclusions

3. Pre-SN: eta Carinae (LBV-star) M~100 M , L~10 6 L 

4. Pre-SN: rho Cassiopeae 3 AU

5. SN 1987A in LMC

7. SNR Cas A in X-ray (Chandra)

8. I.Core collapse supernovae (SNII, Ib, Ic) Hydrogen lines in spectra, variety of light curves End products of evolution of stars with M>8 M  Core collapse  Proto neutron star formation @ ρ~2x10 14 g/cm 3 Bounce shock (Colgate & White 1965) stalls @ R~150-200 km above neutrinosphere and does not lead to explosion due to A) electron deleptonization B) kinetic bounce shock energy spending to nuclear dissociation Need for additional heating (Wilson & Bethe 1985) – neutrino convection (delayed explosion)

17. Delayed SN explosion. Basic picture Proto NS T~10 MeV R PNS ~50-80 km τ ν ~ 2/3 neutrinosphere Neutrino cooling layer (Gain region): Q + ~(L v /r 2 )ε 2 v ΔM~0.01-0.1M  Stalled bounce shock R s ~150-200 km R g ~100 km Mass accretion Neutrino heating layer Q - ~T 6 ~1/r 6

18. Initial energy of explosion: ΔE~(ΔM/m b ) Q + Δt h heating time: Δt h ~(GMm b /rQ + )~ 40 ms This energy triggers outward explosion After shock revival, most additional energy comes from nuclear recombination from nucleons (~8 MeV per nucleon that recombines) Heating ΔM~0.01-0.1 M  yields correct energy of SN explosion! The only problem is how to heat this mass

29. One-dimensional models with detailed neutrino physics fail to explode!

30. Further modifications Accurate treatment of neutrino transport 1D  2D  3D Inclusion of rotation Inclusion of magnetic fields

31. EOS effects (1D calculations) (Janka, Buras, Kifonidis, Marek, Rampp 2004)

32. Comparison of models with Boltzmann neutrino transport (in 1D, 15 M  with relativistic gravity, no explosion) (Liebendoerfer et al. 2004)

37. Multidimensional calculations

38. a) Grid effects Janka et al. 2004 90 o wedge, no explosion 180 o wedge, weak explosion

39. 1200 km 11.2M  : 10 17 flop several months weak explosion… 15M ,simplified neutrino transp.: ΔE~6x10 50 erg b) 2D models are about to make explosion…

40. c) 2D recovers high NS kicks (Scheck et al.2004) NS acceleration by gravitational and hydro forces in direction opposite to low-mode (l=1,2) large-scale convection bubbles

41. First 3D calculations (Scheck et al. 2004) Surf. of const. mass accretion rate per unit area

42. 2D, time-dependent, multi-group, multi-angle radiation hydrodynamics (VULCAN/2D code) (Livne, Burrows, Walder, Lichtenstadt, Thompson 2004). Solves 2D Boltzmann transport equation for neutrino using multi-group energy method along discrete set of representative angular directions Couples radiation field to matter through emission, absorption, scattering and radiation pressure Limitations: no energy redistribution, no velocity-dependence terms Test simulations (only electron neutrinos): 22ms post-bounce, 11 M  progenitor (Woosley & Weaver 1995) (no explosion…) Important finding: emergent neutrino spectrum should be angle-dpendent

43. T=10.2 ms Velocity vectors Lepton number 420 km

44. T=10.2 ms Neutrino flux vectors

45. T=10.2 ms Velocity vectors. Neutrino energy density map 240x240 km

46. T=22ms Velocity vec.

47. T=22 ms Velocity vectors. Neutrino energy density map 420 km

48. T=22 ms Neutrino flux vectors Entropy map 420x420 km

49. T=22 ms Neutrino flux Vectors Energy density map

50. Simple physical conditions for thermal SN explosion 1.Advective timescale across pressure scale: τ Adv =H/V r 2. Net neutrino heating:τ qν =(P/ρ)/(dq ν /dt), dq ν /dt=H ν -C ν Necessary condition for explosion: matter is heated in the gain region faster than is advected from the accreting envelop Sufficient condition for explosion:net heating holds enough time to deposit the binding energy of the overlying mantle (~10 51 ergs)

51. In pure thermal neutrino-driven 1D-models explosions fail because necessary condition τ Adv > τ qv is violated (fresh matter is advected more rapidly than is neutrino-heated). To make an explosion, moderate 25% to 50% increase in the energy deposition rate in the gain region is required

52. No MRI heating (Thompson, Quataert and Burrows 2004) τ adv < τ qv

53. Rotation and viscosity (Thompson, Quataert, Burrows 2004) Rotation is naturally amplified during core collapse Differential rotation may store substantial fraction of gravitational energy released Viscosity in the region of differential rotation (1) transports angular momentum (2) dissipate energy stored in shear on viscous timescale Sources of viscosity: (1) neutrino (found ineffective) (2) turbulence (induced by (a) MRI and (b) hydrodynamic convection )

54. Role of instabilities Main goal: to increase effective neutrino heating Double-diffusion instability inside neutrinosphere (Bruenn et al. 2004) Magneto-rotational instability (MRI) exterior to proto-neutron star (Thomson et al. 2004)

55. Double-diffusion instability: a) Neutron fingers “salt” gradient, destabilizing, slow diffusion “heat” gradient, stabilizing, rapid duffusion In PNS: “salt”  neutron richness (Y e ) “heat”  entropy Unlikely to occur below ν- sphere Gravity gradient

56. Double-diffusion instability: b) lepton semi- convection Gravity gradient “salt” gradient, destabilizing, slow diffusion “heat” gradient, stabilizing, rapid duffusion In PNS: “salt”  neutron richness (Y e ) “heat”  entropy Can produce convection in PNS, increase neutrino luminosity and help explosion

57. Magneto-rotational instability Idea: Velikhov (1959), Chandrasekhar (1960) Applied to accretion disk turbulence by Balbus & Howley (1991-1998) Condition: dΩ 2 /d(lnr) < 0 (ignoring Increment: Γ MRI ~Ω Turbulent viscosity (α-prescription, Shakura & Sunyaev 1973): η MRI =α V t L t =α (ΩH) H = αΩH 2,(α~0.1) Heat generation rate: q MRI =η MRI (r(dΩ/dr)) 2

58. MRI heating included, stalled shock revived

60. Possible signatures of rotation in post-bounce neutrino spectra

61. Asymmetric explosions Evidence: a) strong polarisation of SN emission (esp. type Ib/c without hydrogen shell, e.g 1997X) b) high space velocity (up to 1000 km/s) of young pulsars c) SN1987A: substantial mixing of Ni 56, line profiles asymmetry, light polarisation, direct HST pictures d) young SNR Cas A: asymmetric motion of O-rich clouds, iron-rich layers external to silicon-rich (Chandra), peculiar velocity wrt local ISM (also in other young SNR N132D, E0102.2- 7219 etc.) Mechanisms: a) neutrino asymmetry (parity violation in strong magnetic fields ~10 14 -10 16 G (Chugai 1984). Reproduces pulsar kicks 100-150 km/s b) magnetorotational explosion (Bisnovaty-Kogan 1970) c) SN explosions in binary systems (Blinnikov et al. 1984). Imshennik (1992): rotational instability of rapidly rotating core  binary NS  coalescence  explosion of light NS  large kick velocity of 2d NS

62. Asymmetric models: magnetorotational SN explosion Idea: G.S.Bisnovatyj-Kogan 1970 First successful 2D-calculations (B-K, Moiseenko, Ardeljan 2003-2004) Differential rotation increases toroidal magnetic field  compression MHD wave forms and moves through envelope with steeply decreasing density Initial poloidal magnetic field: E mag ~10 -6 E grav Initial NS spin period: P~0.001 s

63. Velocity field @ t=0.191 s after mag.field turn-on Specific ang. momentum j=v φ r MHD-shock

64. Ejected/rotational energy (~1.12x10 51 ergs) Ejected/total mass (~0.11 M  )

65. II. Thermonuclear supernovae (SNIa) No hydrogen in spectra; similar light curves Rate: 1/100 yrs both in spiral and elliptic galaxies Progenitors: C+O white dwarf with M~M Ch ~1.4 M  (Hoyle & Fowler 1960) “Standard candles” in cosmology (Riess et al.1999,2004) Main problem (until recently): how to obtain explosion and correct nucleosynthetic products? prompt detonation (Arnett 1969) incinerates carbon to iron, deflagration (flame) is too slow (in 1D and 2D), Mach flame ~0.01, star expands and cools How to speed up deflagration? Blinnikov & Sasorov (1996) – Landau-Darrieus flame instability  fractalization of flame front  wrinkles and folds increases front area

66. 3D calculations (Hillebrandt et al.2002-2004, MPA group) of turbulent deflagration, no deflagration-detonation transition is required for successful explosion Ignition conditions: density 2-9x10 9 g/cm 3, temperature >1.5x10 9 K a) 3D model c3_3d_256 (Travaglio et al. 2004) (256x256x256 cells), central ignition; M init (C 12 )=0.475 M , O 16 =0.5 M , Ne 22 =0.025 M 

67. T=0s 10 7 cm Initial front from 2D

68. T=0.2s

69. T=0.4s

70. T=0.6s

71. b) Model b30_3d_768 (Travaglio et al. 2004) (768x768x768 cells), ignition in bubbles within ~100 km (Woosley et al. 2004)

72. T=0s

73. T=0.1s

74. T=0.14s

75. T=0.2s 40% remains unburned

76. Total energy increases in 3D models!

77. Nucleosynthesis yields

78. III. SNIa light curves Form: Radioactive decay of Ni 56 Empirical relation max. brightness – decay rate (Pskovsky 1968) Used in modern cosmology as “standard candles” Sensitive to how degenerate core ignites, Ni 56 yield, rotation, mass … Can probe explosion models! (Sorokina, Blinnikov et al. 2002-2005, multi-group radiation hydrocode STELLA)

79. 2D-models

80. Model: c3_2d_256, Ni 56 mass dependence MBMB

81. Comparison of 2D – 3D models Sorokina, Blinnikov, Hillebrandt et al. 2004

82. Conclusions Core collapse SN: about to explode in 2D. Neutrino-driven convection models: (a) increase in neutrino luminosity by 20-30% due to accurate neutrino transport (Janka et al. 2004) (b) differential rotation and viscosity (convective + MRI turbulence) (Thompson et al.2004) (c) 3D? Magnetorotational mechanism is shown to work in 2D (Bisnovaty-Kogan & Moiseenko 2004)

83. Thermonuclear SN: (a) Turbulent deflagration in 3D produces explosion and correct nucleosynthetic yields (Travaglio et al. 2004). No transition to detonation is required. (b) Light curves (in different colors) are successfully reproduced (STELLA code, Sorokina et al 2004) Neutrino spectra are sensitive to rotation, EOS… and will be invaluable for SN physics