No flares from gamma-ray burst afterglow blast waves encountering sudden circumburst density change

Ilana Gat, Hendrik Van Eerten, Andrew Macfadyen

    Research output: Contribution to journalArticle

    Abstract

    Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power-law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar wind environment that encounters a sudden change in density, followed by a homogeneous medium, and compute the observed radiation using a synchrotron model. We show that flares are not observable for an encounter with a sudden density increase, such as a wind termination shock, nor for an encounter with a sudden density decrease. Furthermore, by extending our analysis to two dimensions, we are able to resolve the spreading, collimation, and edge effects of the blast wave as it encounters the change in circumburst medium. In all cases considered in this paper, we find that a flare will not be observed for any of the density changes studied.

    Original languageEnglish (US)
    Article number2
    JournalAstrophysical Journal
    Volume773
    Issue number1
    DOIs
    StatePublished - Aug 10 2013

    Keywords

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

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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