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Free keywords:
Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE, Astrophysics, Solar and Stellar Astrophysics, astro-ph.SR,General Relativity and Quantum Cosmology, gr-qc
Abstract:
After decades of observations the physical mechanisms that generate short
gamma-ray bursts (SGRBs) still remain unclear. Observational evidence provides
support to the idea that SGRBs originate from the merger of compact binaries,
consisting of two neutron stars (NSs) or a NS and a black hole (BH).
Theoretical models and numerical simulations seem to converge to an explanation
in which the central engine of SGRBs is given by a spinning BH surrounded by a
hot accretion torus. Such a BH-torus system can be formed in compact binary
mergers and is able to launch a relativistic jet, which can then produce the
SGRB. This basic scenario, however, has recently been challenged by Swift
satellite observations, which have revealed long-lasting X-ray afterglows in
association with a large fraction of SGRB events. The long durations of these
afterglows (from minutes to several hours) cannot be explained by the
$\sim\text{s}$ accretion timescale of the torus onto the BH, and, instead,
suggest a long-lived NS as the persistent source of radiation. Yet, if the
merger results in a massive NS the conditions to generate a relativistic jet
and thus the prompt SGRB emission are hardly met. Here we consider an
alternative scenario that can reconcile the two aspects and account for both
the prompt and the X-ray afterglow emission. Implications for future
observations, multi-messenger astronomy and for constraining NS properties are
discussed, as well as potential challenges for the model.
