grb outflows from pop iii stars
Post on 19-Jan-2016
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DESCRIPTIONGRB 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 - PowerPoint PPT Presentation
GRB Outflows from Pop III StarsAimee Hungerford, Gabe RockefellerChris Fryer, Patrick YoungLos Alamos National Laboratory
MotivationCollapsar model is the favored mechanism for long duration GRBsPop III stars naturally satisfy the key ingredients needed for the collapsar modelMassive starLow Metallicity3D Hydro simulations of these objects can provide insight into the properties of GRB ejecta.
OutlineHydro SimulationsFlows dont really show a diskAngular momentum transportOutflow trajectoriesNeutrino EmissionAverage energy and luminosityYe evolution Preliminary Nucleosynthesis
Model(up to t = 5 sec)60 Msun (Hydrogen envelope present)Zero MetallicityFast Rotating (B braking neglected)Accretion Rate (roughly 0.1 Msuns-1)MBH = ~2 Msun boundary at R = 10 kmNewtonian gravity11 x 1051 erg explosion
OutflowsSpiral density wave pattern seen face-on.Convective-like flows are evident in edge-on viewnot very disk-like at all.
Angular Momentum TransportAngular momentum is being transported inward (red) and outward (blue) suggesting very different flow dynamics than those in a typical alpha disk model.
Outflow TrajectorySample trajectories from our 3D collapsar model and a disk wind model (Pruet, Thompson & Hoffman 2004) for comparison.
Neutrino FluxesElectron fraction is reset by neutrinos, but does not achieve the equilibrium (ye near 0.5) implied by luminosity and mean energy of and .
Conclusions3D 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.
Collapse - 60 Solar Mass ProgenitorSet-up and SimulationZero metallicity star2.5 million particles for inner 5 solar masses~100,000-200,000 cpu hours per runNote High Angular Momentum (with respect to the angular momentum of the innermost stable circular orbit) in the first 2 solar masses
GRB mechanism models generally need a rapidly rotating massive star with no hydrogen envelope (jury is still out on whether He can be there). Thus far, the preferred method for getting rapid rotation in the progenitor is to have low mettalicity -> low winds -> low angular momentum loss. Pop III stars provide an ideal testbed for testing out detailed mechanism models, and potentially could be observed by Swift with its ability to detect GRBs at high redshift. Versus radiusbut time would be better.