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Title: A 'BOOSTED FIREBALL' MODEL FOR STRUCTURED RELATIVISTIC JETS

We present a model for relativistic jets which generates a particular angular distribution of Lorentz factor and energy per solid angle. We consider a fireball with specific internal energy E/M launched with bulk Lorentz factor γ {sub B}. In its center-of-momentum frame the fireball expands isotropically, converting its internal energy into radially expanding flow with asymptotic Lorentz factor η{sub 0} ∼ E/M. In the lab frame the flow is beamed, expanding with Lorentz factor Γ = 2η{sub 0}γ {sub B} in the direction of its initial bulk motion and with characteristic opening angle θ{sub 0} ∼ 1/γ {sub B}. The flow is jet-like with Γθ{sub 0} ∼ 2η{sub 0} such that jets with Γ > 1/θ{sub 0} are naturally produced. The choice η{sub 0} ∼ γ {sub B} ∼ 10 yields a jet with Γ ∼ 200 on-axis and angular structure characterized by opening angle θ{sub 0} ∼ 0.1 of relevance for cosmological gamma-ray bursts (GRBs), while γ {sub B} ∼> 1 may be relevant for low-luminosity GRBs. The model produces a family of outflows, of relevance for different relativistic phenomena with structures completely determined by η{sub 0} and γ {sub B}. We calculate the energy per unit solid anglemore » for the model and use it to compute light curves for comparison with the widely used top-hat model. The jet break in the boosted fireball light curve is greatly subdued when compared to the top-hat model because the edge of the jet is smoother than for a top-hat. This may explain missing jet breaks in afterglow light curves.« less
Authors:
;  [1]
  1. Center for Cosmology and Particle Physics, New York University, NY (United States)
Publication Date:
OSTI Identifier:
22215409
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 776; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR DISTRIBUTION; ASYMPTOTIC SOLUTIONS; COSMIC GAMMA BURSTS; HYDRODYNAMICS; LUMINOSITY; RELATIVISTIC RANGE; SHOCK WAVES