## Abstract

We present numerical solutions of the two-dimensional relativistic hydrodynamics equations describing the deceleration and expansion of highly relativistic conical jets, of opening angles 0.05 ≤ θ_{0} ≤ 0.2, propagating into a medium of uniform density. Jet evolution is followed from a collimated relativistic outflow to the quasi-spherical non-relativistic phase. We show that relativistic sideways expansion becomes significant beyond the radius r _{θ} at which the expansion Lorentz factor drops to θ^{-1} _{0}. This is consistent with simple analytic estimates, which predict faster sideways expansion than has been claimed based on earlier numerical modeling. For t > t_{s} = r _{θ}/c the emission of radiation from the jet blast wave is similar to that of a spherical blast wave carrying the same energy (significant deviations at t t_{s} occur only for well off-axis observers, θ_{obs} 1 ≫ θ_{0}). Thus, the total (calorimetric) energy of gamma-ray burst blast waves may be estimated with only a small fractional error based on t > t_{s} observations.

Original language | English |
---|---|

Article number | L23 |

Journal | Astrophysical Journal Letters |

Volume | 738 |

Issue number | 2 |

DOIs | |

Publication status | Published - 10 Sept 2011 |

## All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science