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Nucleosynthesis in jets from Collapsars

Investigating nucleosynthesis in jets from collapsars based on 2D MHD simulations, exploring r-process and masses of 56Ni. Can the diversity in Ni56 mass in GRBs be explained? Discoveries suggest collapses as new r-process sites.

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Nucleosynthesis in jets from Collapsars

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  1. Nucleosynthesis in jets from Collapsars • Shin-ichiro Fujimoto • (KNCT, Japan), • Collaboration with • Nobuya Nishimura, & Masa-aki Hashimoto • (Kyusyu Univ., Japan) OMEG07@Sapporo, Japan 2007.12.04

  2. Collapsar model of gamma-ray bursts Collapsar = Rapidly rotating massive star collapsing to BH (Woosley 1993) • During gravitational collapse of a massive star ( > about 20Msun) • The central core collapses to a black hole (BH) • Outer layersform an accretion disk around BH due to high angular momentum. • Jets from an inner part of the disk. • The jets are accelerated to relativistic velocities. • We can observe a GRB if we locate on directions to jet propagation. Scenario plausible for GRB because of the discovery of GRB with a core collapse supernova (SN) (GRB980425/SN1998bw, GRB030329/SN2003dh)

  3. Based on 2D MHD simulations of collapsars with various distributions of rotation and B fields  Nucleosynthesis in jets from the collapsars R-process & masses of 56Ni No parameters other than initial conditionsof a collapsar before core collapse Motivations • R (rapid neutron capture)-process in collapsar jets • Neutron-rich disk in a collapsar from 1D study • Collapsar = New r-process site ? • Variety ofmasses of 56Ni in SN with nearby GRBs • GRB with hypernova (HN): GRB030329: M(56Ni) > 0.3 Msun • GRB with normal SN: GRB060219: M(56Ni) < 0.1 Msun • GRB without SN: GRB060505: M(56Ni) < 0.01 Msun  Can such the diversity be explained in light of collapsar model ?

  4. Numerical setup in MHD simulations 40Msun collapsar before the core collapse (Hashimoto 1995) Rapid, Moderate, or Slow core Vertical and uniform magnetic fields Angular velocity: R (rapid), M (moderate), S (slow) Magnetic field B0: 108G, 1010G, 1012G 9 collapsars: R8, R10, R12, no ejection of jets M8, M10, M12, ejection of jets S8, S10, S12 rapid moderate slow

  5. Distribution of jet particles: M12 Lagrangian evolution of the jets 3000km x 3000km Tracer particle method ρ,T↑ t=0.20s Lagrangian evolution from Eulerian evolution (M12). • 2,000 tracer particles are initially placed from Fe core to O-rich layers. • We can follow time evolution of position of all tracer particles. • One can select particles (jet particles) that are ejected through the jets. 214 jet particles ρ,T↓ t=0.25s ρ,T↓ t=0.31s the onset of collapse: t = 0 s

  6. Higher density & T states 56Ni produced High density jet particles are expected to be neutron-rich due top+e n Maximum densities and temperatures of jet particles 1e+11 1e+9g/cc Similar to Type II SNe Incomplete Si burning Complete Si burning 1e+06 3e+9 3e+10 1e+9 g/cc B0=1010G Incomplete Si burning Complete Si Burning 3e+9 3e+10 B0=1012G

  7. Ye vs maximum density of jet particles Ye = electron fraction (=electron par baryon) at T = 9e+9 K Ye = 0.4 more n-rich for Ye↓ 1e+9g/cc 1e+06 1e+11 B0=1010G Ye = 0.4 Many n-rich particles for M10, M12, & R12 1e+9g/cc R-process is expected to operate 1e+06 1e+11 B0=1012G

  8. M10 R12 M12 Composition of collapsar jets and Eu-scaled solar r-elements ■: Collapsar jets □: Eu-scaled solar r-nuclei Abundance profiles of collapsar jets are similar to those of the solar r-elements for A > 80-100 U,Th U,Th U,Th A=80 A=80

  9. Enegetic jet with r-elements 0.12 & 0.3 Msun/s Ejected masses of 56Ni & r-elements Bright SNe (HNe) Normal SNe Weak or no SNe M(56Ni)ej↑ for Eej↑ Bright-ness of SNe Eej [1051 ergs]

  10. Summary We have investigated nucleosynthesis inside the jets from collapsars, based on 2D MHD simulations of the collapsars in light of the collapsar model of GRBs • R-process in the jets • R-process in the energetic jets (Eej > 1051ergs) from three collapsars (M10, M12, R12) • Even for a collapsar (M10) with moderate rotation (2.5Hz) and 1010G • Large amounts of r-nuclei (> 0.01Msun) • Masses of 56Ni in the jets • Jets with Eej ↑,Mass of56Ni ↑ • The diversity of Ni56 mass in GRBs is likely to be explained in light of the collapsar model ApJ644, 1040, 2006 (MHD), ApJ656, 382, 2007 (r-proc.)

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