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We recall evidence that long gamma-ray bursts (GRBs) have binary progenitors and give new examples. Binary-driven hypernovae (BdHNe) consist of a carbon–oxygen core (COcore) and a neutron star (NS) companion. For binary periods ∼5 min, the COcore collapse originates the subclass BdHN I characterized by (1) an outstanding supernova (SN; the ' SN-rise '); (2) a black hole (BH), born from the NS collapse by SN matter accretion, leading to a GeV emission with luminosity |$L_{\rm GeV} = A_{\rm GeV}\, t^{-\alpha _{\rm GeV}}$|⁠ , observed only in some cases; and (3) a new NS (νNS), born from the SN, originating from the X-ray afterglow with |$L_\mathrm{ X} = A_{\rm X}\, t^{-\alpha _{\rm X}}$|⁠ , observed in all BdHN I. We record 378 sources and present for four prototype GRBs 130427A, 160509A, 180720B, and 190114C: (1) spectra, luminosities, SN-rise duration; (2) A X, αX = 1.48 ± 0.32, and (3) the νNS spin time evolution. We infer (i) A GeV, αGeV = 1.19 ± 0.04 and (ii) the BdHN I morphology from time-resolved spectral analysis, three-dimensional simulations, and the GeV emission presence/absence in 54 sources within the Fermi -Large Area Telescope boresight angle. For 25 sources, we give the integrated and time-varying GeV emission, 29 sources have no GeV emission detected and show X/gamma-ray flares previously inferred as observed along the binary plane. The 25/54 ratio implies the GeV radiation is emitted within a cone of half-opening angle ≈60° from the normal to the orbital plane. We deduce BH masses of 2.3–8.9 M⊙ and spin of 0.27–0.87 by explaining the GeV emission from the BH rotational energy extraction, while their time evolution validates the BH mass–energy formula. [ABSTRACT FROM AUTHOR]

Short and long-duration gamma-ray bursts (GRBs) have been recently sub-classified into seven families according to the binary nature of their progenitors. For short GRBs, mergers of neutron star binaries (NS-NS) or neutron star-black hole binaries (NS-BH) are proposed. For long GRBs, the induced gravitational collapse (IGC) paradigm proposes a tight binary system composed of a carbon-oxygen core (CO) and a NS companion. The explosion of the CO as supernova (SN) triggers a hypercritical accretion process onto the NS companion which might reach the critical mass for the gravitational collapse to a BH. Thus, this process can lead either to a NS-BH or to NS-NS depending on whether or not the accretion is sufficient to induce the collapse of the NS into a BH. We shall discuss for the above compact object binaries: (1) the role of the NS structure and the equation-of-state on their final fate; (2) their occurrence rates as inferred from the X and gamma-ray observations; (3) the expected number of detections of their gravitational wave (GW) emission by the Advanced LIGO interferometer. [ABSTRACT FROM AUTHOR]

Context. The induced gravitational collapse (IGC) scenario has been introduced in order to explain the most energetic gamma ray bursts (GRBs), Eiso = 1052-1054 erg, associated with type Ib/c supernovae (SNe). It has led to the concept of binary-driven hypernovae (BdHNe) originating in a tight binary system composed by a FeCO core on the verge of a SN explosion and a companion neutron star (NS). Their evolution is characterized by a rapid sequence of events: 1) the SN explodes, giving birth to a new NS (vNS). The accretion of SN ejecta onto the companion NS increases its mass up to the critical value; 2) the consequent gravitational collapse is triggered, leading to the formation of a black hole (BH) with GRB emission; 3) a novel feature responsible for the emission in the GeV, X-ray, and optical energy range occurs and is characterized by specific power-law behavior in their luminosity evolution and total spectrum; 4) the optical observations of the SN then occurs. Aims. We investigate whether GRB 090423, one of the farthest observed GRB at z = 8:2, is a member of the BdHN family. Methods. We compare and contrast the spectra, the luminosity evolution, and the detectability in the observations by Swift of GRB 090423 with the corresponding ones of the best known BdHN case, GRB 090618. Results. Identification of constant slope power-law behavior in the late X-ray emission of GRB 090423 and its overlapping with the corresponding one in GRB 090618, measured in a common rest frame, represents the main result of this article. This result represents a very significant step on the way to using the scaling law properties, proven in Episode 3 of this BdHN family, as a cosmological standard candle. Conclusions. Having identified GRB 090423 as a member of the BdHN family, we can conclude that SN events, leading to NS formation, can already occur, namely at 650 Myr after the Big Bang. It is then possible that these BdHNe stem from 40-60 M☉ binaries. They are probing the Population II stars after the completion and possible disappearance of Population III stars. [ABSTRACT FROM AUTHOR]

Context. The induced gravitational collapse (IGC) paradigm addresses the very energetic (1052-1054 erg) long gamma-ray bursts (GRBs) associated to supernovae (SNe). Unlike the traditional "collapsar" model, an evolved FeCO core with a companion neutron star (NS) in a tight binary system is considered as the progenitor. This special class of sources, here named "binary-driven hypernovae" (BdHNe), presents a composite sequence composed of four different episodes with precise spectral and luminosity features. Aims. We first compare and contrast the steep decay, the plateau, and the power-law decay of the X-ray luminosities of three selected BdHNe (GRB 060729, GRB 061121, and GRB 130427A). Second, to explain the different sizes and Lorentz factors of the emitting regions of the four episodes, for definiteness, we use the most complete set of data of GRB 090618. Finally, we show the possible role of r-process, which originates in the binary system of the progenitor. Methods. We compare and contrast the late X-ray luminosity of the above three BdHNe. We examine correlations between the time at the starting point of the constant late power-law decay t*a , the average prompt luminosity 〈Liso〉, and the luminosity at the end of the plateau La. We analyze a thermal emission (~0:97-0:29 keV), observed during the X-ray steep decay phase of GRB 090618. Results. The late X-ray luminosities of the three BdHNe, in the rest-frame energy band 0:3-10 keV, show a precisely constrained "nested" structure. In a space-time diagram, we illustrate the different sizes and Lorentz factors of the emitting regions of the three episodes. For GRB 090618, we infer an initial dimension of the thermal emitter of ~7 × 1012 cm, expanding at Γ ≈ 2. We find tighter correlations than the Dainotti-Willingale ones. Conclusions. We confirm a constant slope power-law behavior for the late X-ray luminosity in the source rest frame, which may lead to a new distance indicator for BdHNe. These results, as well as the emitter size and Lorentz factor, appear to be inconsistent with the traditional afterglow model based on synchrotron emission from an ultra-relativistic (Γ ~ 10²-10³) collimated jet outflow. We argue, instead, for the possible role of r-process, originating in the binary system, to power the mildly relativistic X-ray source. [ABSTRACT FROM AUTHOR]

Context. It has been proposed that the temporal coincidence of a gamma-ray burst (GRB) and a type Ib/c supernova (SN) can be explained with the concept of induced gravitational collapse (IGC), induced by the matter ejected from an SN Ib/c accreting onto a neutron star (NS). The NS is expected to reach the critical mass necessary for it to collapse to a black hole (BH) and emit a GRB. We found a standard luminosity light curve behavior in the late-time X-ray emission of this subclass of GRBs. Aims. We test if this standard behavior in the luminosity found in this subclass of GRBs can become a redshift estimator of these sources. Methods. We selected a sample of GRBs that belong to this subclass of IGC GRBs associated to an SN (IGC GRB-SN sources). These sources have an isotropic energy Eiso > 1052 erg and their cosmological redshifts are in the range of z = 0.49-1.261. We focused on the corresponding X-ray luminosity light curves. Results. We find that all 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 used these results to estimate the GRB redshift of the sample without a measured redshift and found results consistent with other possible redshift indicators. Conclusions. The standard late-time X-ray luminosity light curve of all GRBs of the sample shows 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 moreover represents strong evidence of very low or even absent beaming in this late phase of the X-ray afterglow emission process. This could be a fundamental tool for estimating the redshift of GRBs that belong to this subclass of events. We are currently expanding this subclass of GRBs to further verify the universal validity of this new redshift estimation method. [ABSTRACT FROM AUTHOR]

Context. Gamma-ray burst (GRB) 110709B is the first source for which Swift-BAT was triggered twice, with a time separation of ~10 min. The first emission (called here episode 1) lasted from 40 s before the first trigger time until 60 s after it. The second emission (hereafter episode 2) lasted from 35 s before the second trigger time until 100 s after it. These features reproduce those of GRB 090618, which has recently been interpreted within the induced gravitational collapse (IGC) paradigm. In line with this paradigm, we assume the progenitor to be a close binary system composed of the core of an evolved star and a neutron star (NS). The evolved star explodes as a supernova (SN) and ejects material that is partially accreted by the NS. We identify this process with episode 1. The accretion process accumulates more than the critical mass of the NS, which gravitationally collapses into a black hole (BH). This process leads to the GRB emission, episode 2. The two trigger episodes have for the first time provided the possibility to cover the X-ray emission observed by XRT both prior to and during the prompt phase of GRB 110709B. Aims. We analyze the spectra and time variability of episodes 1 and 2 and compute the relevant parameters of the binary progenitor, as well as the astrophysical parameters both in the SN and the GRB phase in the IGC paradigm. Methods. We performed a time-resolved spectral analysis of episode 1 by fitting the spectrum with a blackbody (BB) plus a power-law (PL) spectral model. From the BB fluxes and temperatures of episode 1 and the luminosity distance dL, we evaluated the evolution with time of the radius of the BB emitter, associated here to the evolution of the SN ejecta.We analyzed episode 2 within the fireshell model, identifying the proper GRB (P-GRB) and simulating the light curve and spectrum. We established the redshift to be z = 0.75, following the phenomenological methods described in the literature, and our analysis of the late X-ray afterglow. It is most remarkable that the determination of the cosmological redshift on the basis of scaling the late X-ray afterglow, which was already verified in GRB 090618 and GRB 101023, is again verified by this analysis. Results. We find for episode 1 a temperature of the BB component that evolves with time following a broken PL, with the slope of the PL at early times α = 0 (constant function) and the slope of the PL at late times β = -4 ± 2. The break occurs at t = 41.21 s. The total energy of episode 1 is E(1)iso = 1.42 × 1053 erg. The total energy of episode 2 is E(2)iso = 2.43 × 1052 erg. We find at transparency a Lorentz factor Γ ~ 1.73 × 102, laboratory radius of 6.04 × 1013 cm, P-GRB observed temperature kTP-GRB = 12.36 keV, baryon load B = 5.7 × 10-3 and P-GRB energy of EP-GRB = 3.44 × 1050 erg. We find a remarkable coincidence of the cosmological redshift by scaling the XRT data and with three other phenomenological methods. Conclusions. We interpret GRB 110709B as a member of the IGC sources, together with GRB 970828, GRB 090618, and GRB 101023. The existence of the XRT data during the prompt phase of the emission of GRB 110709B (episode 2) offers an unprecedented tool for improving the diagnostic of GRBs emission. [ABSTRACT FROM AUTHOR]

We performed a data analysis of the observations by the Swift, NuStar, and Fermi satellites in order to probe the induced gravitational collapse (IGC) paradigm for gamma-ray bursts (GRBs) associated with supernovae (SNe) in the terra incognita of GRB 130427A. We compare our data analysis with those in the literature. We have verified that GRB 130427A conforms to the IGC paradigm by examining the power law behavior of the luminosity in the early 104 s of the XRT observations. This has led to the identification of the four different episodes of the binary driven hypernovae (BdHNe) and to the prediction, on 2013 May 2, of the occurrence of SN 2013cq, which was also observed in the optical band on 2013 May 13. The exceptional quality of the data has allowed the identification of novel features in Episode 3 including: (1) the confirmation and the extension of the existence of the recently discovered nested structure in the late X-ray luminosity in GRB 130427A, as well as the identification of a spiky structure at 102 s in the cosmological rest-frame of the source; (2) a power law emission of the GeV luminosity light curve and its onset at the end of Episode 2; and (3) different Lorentz Γ factors for the emitting regions of the X-ray and GeV emissions in this Episode 3. These results make it possible to test the details of the physical and astrophysical regimes at work in the BdHNe: (1) a newly born neutron star and the supernova ejecta, originating in Episode 1; (2) a newly formed black hole originating in Episode 2; and (3) the possible interaction among these components, observable in the standard features of Episode 3. [ABSTRACT FROM AUTHOR]