EPJ Web of Conferences 168, 04008 (2018)
https://doi.org/10.1051/epjconf/201816804008

GRB 110731A within the IGC paradigm

¹ Dipartimento di Fisica and ICRA, Sapienzà Universita di Roma, Piazzale Aldo Moro 5, I–00185 Rome, Italy
² ICRANet, Pizza della Repubblica 10, I–65122 Pescara, Italy
³ Université de Nice Sophia Antipolis, CEDEX 2, Grand Château Parc Valrose, Nice, France
⁴ ICRANet-Rio, Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290–180 Rio de Janeiro, Brazil
⁵ ASI Science Data Center, Via del Politecnico s.n.c., I-00133 Rome, Italy
⁶ Dept. of Physical Sciences, Earth and Environment, University of Siena, Via Roma 56, I-53100 Siena, Italy

^* e-mail: Daria.Primorac@icranet.org
^** e-mail: ruffini@icra.it
^*** e-mail: giovanni.b.pisani@gmail.com

Published online: 9 January 2018

Abstract

Bright gamma-ray burst (GRB) 110731A was simultaneously observed by Fermi and Swift observatories, with a follow up optical observation which inferred the redshift of z = 2.83. Thus, available data are spanning from optical to high energy (GeV) emission. We analyze these data within the induced gravitational collapse (IGC) paradigm, recently introduced to explain temporal coincidence of some long GRBs with type Ic supernovae. The case of binary-driven hypcrnova (BdHN) assumes a close system, which starts as an evolved core - neutron star binary. After the core-collapse event, the new NS - black hole system is formed, emitting the GRB in the process. We performed the time-resolved and time-integrated analysis of the Fermi data. Preliminary results gave isotropic energy E_iso = 6.05 × 10⁵³ erg and the total P-GRB energy of E_p–GRB = 3.7 × 10⁵² erg. At transparency point we found a Lorentz factor Γ ~ 2.17 × 10³ laboratory radius of 8.33 x 10¹³ cm, P-GRB observed temperature of 168 keV and a baryon load B = 4.35 × 10^-4. Simulated light-curve and prompt emission spectra showed the average circum burst medium density to be n ~ 0.03 particles per cm³. We reproduced the X-ray light-curve within the rest-frame of the source, finding the common late power-law behavior, with α = –1.22. Considering these results, we interpret GRB 110731A as a member of a BdHNe group.