GRB 140619B: A short GRB from a binary neutron star merger leading to black hole formation

Description

For short gamma-ray bursts (GRBs), double neutron star (NS) mergers are traditionally adopted as progenitors. We propose a classification of short bursts into two sub-classes: short gamma-ray flashes (S-GRFs) with isotropic energy E_iso ≲ 10⁵² erg and rest-frame spectral peak energy E_p,i ≲ 2 MeV, when the merger leads to a very massive NS (MNS), and the authentic short GRBs (S-GRBs) with E_iso ≳ 10⁵² erg and E_p,i ≳ 2 MeV, when a black hole (BH) is formed. Evidences for the BH formation in S-GRBs are provided by the observed high energy 0.1–100 GeV emission after the GRB emission from the e⁺e⁻-plasma transparency (P-GRB); in S-GRFs, leading to MNS, this emission is never observed. Both these sub-classes fulfill the E_p,i–E_iso relation for short GRBs. We present here the recently identified S-GRB 140619B. From the spectral analysis of the early ∼ 0.2 s, we infer an observed P-GRB temperature kT = (324 ± 33) keV, a theoretically derived redshift z = 2.67 ± 0.37, a total burst energy erg, and a baryon load B = (5.52 ± 0.73) × 10⁻⁵. We also estimate the emission of gravitational waves (GWs) of the progenitor NS–NS merger. Including all the S-GRBs so far identified, the observed rate of these sources is

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