On the duration of long GRBs: effects of black hole spin

Abstract

In the frame of the collapsar model for long gamma ray bursts (GRBs), we investigate the formation of a torus around a spinning BH and we check what rotational properties a progenitor star must have in order to sustain torus accretion over relatively long activity periods. We also study the time evolution of the BH spin parameter. We take into account the coupling between BH mass, its spin parameter and the critical specific angular momentum of accreting gas, needed for the torus to form. The large BH spin reduces the critical angular momentum which in turn can increase the GRB duration with respect to the Schwarzschild BH case. We quantify this effect and estimate the GRB durations in three cases: when a hyper accreting torus operates or a BH spins very fast or both. We show under what conditions a given progenitor star produces a burst that can last as short as several seconds and as long as several hundred of seconds. Our models indicate that it is possible for a single collapse to produce three kinds of jets: (1) a very short, lasting between a fraction of a second and a few seconds, 'precursor' jet, powered only by a hyper accreting torus before the BH spins up, (2) an 'early' jet, lasting several tens of seconds and powered by both hyper accretion and BH rotation, and (3) a 'late' jet, powered only by the spinning BH.

13 pages; 9 figures; ApJ in press

References in corpus (6)

• Black Hole Spin Evolution: Implications for Short-hard Gamma Ray Bursts and Gravitational Wave Detection
• Gamma-Ray Bursts from tidally spun-up Wolf-Rayet stars?
• Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts
• GRB Precursors in the Fallback Collapsar Scenario
• Low angular momentum accretion in the collapsar: how long can a long GRB be?
• Observations of the intense and ultra-long burst GRB041219a with the Germanium Spectrometer on INTEGRAL

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• Episodic jet power extracted from a spinning black hole surrounded by a neutrino-dominated accretion flow in gamma-ray bursts
• Self-gravitating collapsing star and black hole spin-up in long gamma ray bursts
• Exploring GRBs and supernovae connection: does a superluminous hypernova population exist?
• Black hole accretion in gamma ray bursts