Gamma-Ray Burst Jets: dynamics and interaction with the progenitor star Davide Lazzati, Brian Morsony, and Mitch Begelman JILA - University of Colorado Davide Lazzati, Brian Morsony, and Mitch Begelman JILA - University of Colorado

Evidence for SN association SN2003dh Stanek et al Hjorth et al SN1998bw Galama et al. 1998

Phases of jet propagation Confined Jet Shock breakout Shocked jet Unshocked jet

I: confined jet Jet head propagates under ram pressure equilibrium No mixing between shocked jet and star material Cocoon is over-pressured and drives shock into stellar material. Shock expands under Kompaneets approximation v sh ~(p cocoon /  star ) 1/2. Cocoon cools adiabatically (relativistic EOS). Jet reacts to cocoon pressure with internal and ram pressure terms. Acceleration  ~p -1/4. Lazzati & Begelman 2005

I: confined jet In a monolithic jet the pressure scales with working surface P~  -1/2 Simulations show the monolithic approximation to be inaccurate. A boundary layer develops. Jet free inside, the velocity is parallel to the boundary in the layer z rr

II: Shock breakout Is the first radiative phase: hot non- relativistic material is released on the stellar surface Ramirez-Ruiz et al MacFadyen et al Zhang et al. 2003

III: Shocked Jet The jet in this phase is heavily affected by the transversal collimation shocks.

IV: Unshocked Jet The evolution can be computed analogously to the confined jet geometry but now the cocoon pressure decreases with time. The opening angle of the jet grows with time

Analytic vs. Numeric

Cocoon pressure and breakout time are very well reproduced. Jet opening angle works better for jet initially out of causal contact (due to hyper- relativistic approximations). Energy stored in the cocoon: 8x10 50 vs. 9x10 50

Analytic Results The break-out opening angle is smaller for more massive and large stars A jet with initial opening angle of 10 o and  =10 is propagated through polytropic stars of varying mass and radius. WRPopIII

Analytic Results A jet with initial opening angle of 10 o and  =10 is propagated through polytropic stars of varying mass and radius. WRPopIII The break-out time depends very mildly on the mass, so too the energy deposited into the star

Analytic Results Assuming  =0.3 is a good approximation in most cases. As a consequence massive compact stars will NOT explode due to the jet propagation GRBs without SN? Exploding Stars Non exploding (no SN?)

Numerical : movies

Numerical Results

Different observers see GRBs dominated by a different phase Small angles are dominated by shocked jet. Intermediate angles are dominated by unshocked jet Large angles are dominated by cocoon

Numerical Results Precursor Dead times X-ray flash

Summary  A simple pressure balance explains some features of the jet/cocoon/star interaction and allows quantitative computations  Jet can propagate fast in very massive stars if compact (  ~0.3 robust). PopIII GRBs?  Jet propagation takes place in 4 phases: 3 radiative  Cocoon = Precursor but we do not see shocked or un-shocked jet. Different observers are however dominated by different phases.  Even a constant luminosity at the base can produce very complex time histories at the stellar surface.  A simple pressure balance explains some features of the jet/cocoon/star interaction and allows quantitative computations  Jet can propagate fast in very massive stars if compact (  ~0.3 robust). PopIII GRBs?  Jet propagation takes place in 4 phases: 3 radiative  Cocoon = Precursor but we do not see shocked or un-shocked jet. Different observers are however dominated by different phases.  Even a constant luminosity at the base can produce very complex time histories at the stellar surface.