Some members of the Induced Gravitational Collapse (IGC) family

Author: Ana Virginia Penacchioni

Abstract: The Induced Gravitational Collapse (IGC) model describes a particular family of Gamma-ray bursts (GRBs). It relates the emission we see from some long GRBs to a close binary system formed by a massive star on the verge of a Supernova (SN) and a Neutron Star (NS). There is a well-determined time sequence in the evolution of the system: 1) The massive star (possibly a CO star) undergoes a SN explosion, 2) part of the material that reaches the NS capture region is accreted by the NS companion, 3) the NS reaches its critical mass and collapses to a black hole (BH), 4) the GRB is emitted.

We have already examined two GRBs that belong to this family, GRB 101023 and GRB 110709B, which we present here. GRB 101023 has a total isotropic energy of Eiso=1.3E53 erg and GRB 110709B has Eiso=2.72E53 erg. Their light curves present two well separated episodes. There is no measured redshift for these sources, so we inferred it using different empirical methods, by Amati, by Yonetoku and by Grupe, and our analysis of the late X-ray afterglow. We found that the redshift found with this last method is in agreement with the values found with the other empirical methods. We describe each episode of emission within the IGC scenario and compute the relevant parameters of the binary system. The importance of this model lies in the fact that it enables us to predict whether there is an associated SN within the first hours of the GRB emission.

We are now enlarging the sample, extending to different redshifts, and covering a wider energy range. Results will be presented.