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GRB Outflows from Pop III Stars

GRB Outflows from Pop III Stars. Aimee Hungerford, Gabe Rockefeller Chris Fryer, Patrick Young Los Alamos National Laboratory. Motivation. Collapsar model is the favored mechanism for long duration GRBs Pop III stars naturally satisfy the key ingredients needed for the collapsar model

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GRB Outflows from Pop III Stars

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  1. GRB Outflows from Pop III Stars Aimee Hungerford, Gabe Rockefeller Chris Fryer, Patrick Young Los Alamos National Laboratory

  2. Motivation • Collapsar model is the favored mechanism for long duration GRBs • Pop III stars naturally satisfy the key ingredients needed for the collapsar model • Massive star • Low Metallicity • 3D Hydro simulations of these objects can provide insight into the properties of GRB ejecta.

  3. Outline • Hydro Simulations • Flows don’t really show a disk • Angular momentum transport • Outflow trajectories • Neutrino Emission • Average energy and luminosity • Ye evolution • Preliminary Nucleosynthesis

  4. Model(up to t = 5 sec) • 60 Msun (Hydrogen envelope present) • Zero Metallicity • Fast Rotating (B braking neglected) • Accretion Rate (roughly 0.1 Msuns-1) • MBH = ~2 Msun • boundary at R = 10 km • Newtonian gravity • 11 x 1051 erg explosion

  5. Outflows Spiral density wave pattern seen face-on. Convective-like flows are evident in edge-on view…not very “disk-like” at all.

  6. Angular Momentum Transport Angular momentum is being transported inward (red) and outward (blue) suggesting very different flow dynamics than those in a typical alpha disk model.

  7. Outflow Trajectory Sample trajectories from our 3D collapsar model and a disk wind model (Pruet, Thompson & Hoffman 2004) for comparison.

  8. Neutrino Fluxes • Electron fraction is reset by neutrinos, but does not achieve the equilibrium (ye near 0.5) implied by luminosity and mean energy of and .

  9. Nucleosynthesis

  10. Conclusions • 3D engine structure seems to be more complicated than expected. • Very energetic explosion is launched (even without a jet component.) • Electron fraction is uncertain and sets the nucleosynthesis of the outflow material. • “classical” r-process synthesis seems unlikely.

  11. Set-up and Simulation Zero metallicity star 2.5 million particles for inner 5 solar masses ~100,000-200,000 cpu hours per run Note High Angular Momentum (with respect to the angular momentum of the innermost stable circular orbit) in the first 2 solar masses Collapse - 60 Solar Mass Progenitor

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