Observational implications of gamma-ray burst afterglow jet simulations and numerical light curve calculations

Hendrik J. Van Eerten, Andrew I. MacFadyen

    Research output: Contribution to journalArticle

    Abstract

    We discuss jet dynamics for narrow and wide gamma-ray burst (GRB) afterglow jets and the observational implications of numerical simulations of relativistic jets in two dimensions. We confirm earlier numerical results that sideways expansion of relativistic jets during the bulk of the afterglow emission phase is logarithmic in time and find that this also applies to narrow jets with half opening angle of 0.05 rad. As a result, afterglow jets remain highly nonspherical until after they have become nonrelativistic. Although sideways expansion steepens the afterglow light curve after the jet break, the jet edges becoming visible dominates the jet break, which means that the jet break is sensitive to the observer angle even for narrow jets. Failure to take the observer angle into account can lead to an overestimation of the jet energy by up to a factor of four. This weakens the challenge posed to the magneter energy limit by extreme events such as GRB090926A. Late-time radio calorimetry based on a spherical nonrelativistic outflow model remains relevant when the observer is approximately on-axis and where differences of a few in flux level between the model and the simulation are acceptable. However, this does not imply sphericity of the outflow and therefore does not translate to high observer angles relevant to orphan afterglows. For more accurate calorimetry and in order to model significant late-time features such as the rise of the counterjet, detailed jet simulations remain indispensable.

    Original languageEnglish (US)
    Article number155
    JournalAstrophysical Journal
    Volume751
    Issue number2
    DOIs
    StatePublished - Jun 1 2012

    Fingerprint

    afterglows
    gamma ray bursts
    light curve
    simulation
    calorimetry
    calculation
    outflow
    heat measurement
    orphan
    expansion
    extreme event
    energy
    radio

    Keywords

    • gamma-ray burst: general
    • hydrodynamics
    • methods: numerical
    • relativistic processes - shock waves

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Observational implications of gamma-ray burst afterglow jet simulations and numerical light curve calculations. / Van Eerten, Hendrik J.; MacFadyen, Andrew I.

    In: Astrophysical Journal, Vol. 751, No. 2, 155, 01.06.2012.

    Research output: Contribution to journalArticle

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