GRB 090510: A genuine short GRB from a binary neutron star coalescing into a Kerr-Newman black hole

RUFFINI, R.; MUCCINO, M.; AIMURATOV, Y.; BIANCO, C.L.; CHERUBINI, C.; ENDERLI, M.; KOVACEVIC, M.; MORADI, R.; PENACCHIONI, A.V.; PISANI, G.B.; RUEDA, J.A.; WANG, Y.

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Año: 2016 vol. 831

0004-637X

In a new classification of merging binary neutron stars (NSs) we separate short gamma-ray bursts (GRBs) into two subclasses. The ones with E iso ≲ 10 52 erg coalesce to form a massive NS and are indicated as short gamma-ray flashes (S-GRFs). The hardest, with E iso ≳ 10 52 erg, coalesce to form a black hole (BH) and are indicated as genuine short GRBs (S-GRBs). Within the fireshell model, S-GRBs exhibit three different components: the proper GRB (P-GRB) emission, observed at the transparency of a self-accelerating baryon-e + e - plasma; the prompt emission, originating from the interaction of the accelerated baryons with the circumburst medium; and the highenergy (GeV) emission, observed after the P-GRB and indicating the formation of a BH. GRB 090510 gives the first evidence for the formation of a Kerr BH or, possibly, a Kerr-Newman BH. Its P-GRB spectrum can be fitted by a convolution of thermal spectra whose origin can be traced back to an axially symmetric dyadotorus. A large value of the angular momentum of the newborn BH is consistent with the large energetics of this S-GRB, which reach in the 1-10,000 keV range E iso = (3.95±0.21) × 10 52 erg and in the 0.1-100 GeV range E LAT = (5.78±0.60) × 10 52 erg, the most energetic GeV emission ever observed in S-GRBs. The theoretical redshift z th =0.75±0.17 that we derive from the fireshell theory is consistent with the spectroscopic measurement z=0.903±0.003, showing the self-consistency of the theoretical approach. All S-GRBs exhibit GeV emission, when inside the Fermi-LAT field of view, unlike S-GRFs, which never evidence it. The GeV emission appears to be the discriminant for the formation of a BH in GRBs, confirmed by their observed overall energetics.