A narrow short-duration GRB JET from a wide central engine

Paul C. Duffell, Eliot Quataert, Andrew I. Macfadyen

    Research output: Contribution to journalArticle

    Abstract

    We use two-dimensional relativistic hydrodynamic numerical calculations to show that highly collimated relativistic jets can be produced in neutron star merger models of short-duration gamma-ray bursts (GRBs) without the need for a highly directed engine or a large net magnetic flux. Even a hydrodynamic engine generating a very wide sustained outflow on small scales can, in principle, produce a highly collimated relativistic jet, facilitated by a dense surrounding medium that provides a cocoon surrounding the jet core. An oblate geometry to the surrounding gas significantly enhances the collimation process. Previous numerical simulations have shown that the merger of two neutron stars produces an oblate, expanding cloud of dynamical ejecta. We show that this gas can efficiently collimate the central engine power much like the surrounding star does in long-duration GRB models. For typical short-duration GRB central engine parameters, we find jets with opening angles of an order of 10° in which a large fraction of the total outflow power of the central engine resides in highly relativistic material. These results predict large differences in the opening angles of outflows from binary neutron star mergers versus neutron star-black hole mergers.

    Original languageEnglish (US)
    Article number64
    JournalAstrophysical Journal
    Volume813
    Issue number1
    DOIs
    StatePublished - Nov 1 2015

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    Keywords

    • ISM: jets and outflows
    • gamma-ray burst: general
    • hydrodynamics
    • relativistic processes
    • shock waves

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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