On a novel distance indicator for gamma-ray bursts associated with supernovae

Author: Giovanni Battista Pisani

Abstract: It has been proposed that the temporal coincidence of a gamma-ray burst (GRB) and a type Ib/c supernova (SN) can be explained by the concept of induced gravitational collapse (IGC), induced by the matter ejected from a SN Ib/c accreting onto a neutron star (NS). The NS is expected to reach its critical mass to collapse to a black hole (BH) and emit a GRB. A standard luminosity light curve behavior in the late time X-ray emission of this subclass of GRBs is found. We build a sample of GRBs belonging to this subclass of IGC GRBs associated to a SN (IGC GRB-SN sources). The selected sources have an isotropic energy Eiso > 1052 erg and their cosmological redshifts are in the range z = 0.49 - 1.261. We focus the attention on the corresponding X-ray luminosity light curves. We find that all the GRBs of the sample with measured redshift present a standard luminosity late time light curve in the 0.3 - 10 keV rest frame energy range. We also use these results to estimate the redshift of the GRBs of the sample with no measured redshift, finding consistent results with alternative redshift indicators. The standard late time X-ray luminosity light curve of all the GRBs of the sample presents a common physical mechanism in this particular phase of the X-ray emission, possibly related to the creation of the NS from the SN process. This scaling law allows us to predict in advance the cosmological redshift of the IGC sources and the presence of the associated SN, whether detectable or not. Moreover, this result represents a strong evidence of very low or even absent beaming in this late phase of the X-ray afterglow emission process. We are enlarging the number of this sub-class of GRBs to further verify the universal validity of this new redshift estimation method.