Long-duration gamma-ray bursts: hydrodynamic instabilities in collapsar discs

Abstract

We present 3D numerical simulations of the early evolution of long-duration gamma-ray bursts in the collapsar scenario. Starting from the core collapse of a realistic progenitor model, we follow the formation and evolution of a central black hole and centrifugally balanced disc. The dense, hot accretion disc produces freely escaping neutrinos and is hydrodynamically unstable to clumping and to forming non-axisymmetric (m = 1, 2) modes. We show that these spiral structures, which form on dynamical time-scales, can efficiently transfer angular momentum outwards and can drive the high required accretion rates (≥0.1–1 M⊙ s−1) for producing a jet. We utilize the smoothed particle hydrodynamics code, gadget-2, modified to implement relevant microphysics, such as cooling by neutrinos, a plausible treatment approximating the central object and relativistic effects. Finally, we discuss implications of this scenario as a source of energy to produce relativistically beamed γ-ray jets.