Maxime Enderli

On binary-driven hypernovae and their nested late X-ray emission

The induced gravitational collapse (IGC) paradigm addresses energetic (1052-1054 erg), long gamma-ray bursts (GRBs) associated to supernovae (SNe) and proposes as their progenitors tight binary systems composed of an evolved FeCO core and a companion neutron star (NS). Their emission is characterized by four specific episodes: Episode 1, corresponding to the on-set of the FeCO SN explosion and the accretion of the ejecta onto the companion NS; Episode 2, related the collapse of the companionNS to a black hole (BH) and to the emission of a long GRB; Episode 3, observed in X-rays and characterized by a steep decay, a plateau phase and a late power-law decay; Episode 4, corresponding to the optical SN emission due to the 56Ni decay. We focus on Episode 3 and we show that, from the thermal component observed during the steep decay of the prototype GRB 090618, the emission region has a typical dimension of ~1013 cm, which is inconsistent with the typical size of the emitting region of GRBs, e.g., ~1016 cm. We propose, therefore, that the X-ray afterglow emission originates from a spherically symmetric SN ejecta expanding at G ˜ 2 or, possibly, from the accretion onto the newly formed black hole, and we name these systems “binary driven hypernovae” (BdHNe). This interpretation is alternative to the traditional afterglow model based on the GRB synchrotron emission from a collimated jet outflow, expanding at ultra-relativistic Lorentz factor of G ~ 102-103 and originating from the collapse of a single object. We show then that the rest-frame energy band 0.3-10 keV X-ray luminosities of three selected BdHNe, GRB 060729, GRB 061121, and GRB 130427A, evidence a precisely constrained “nested” structure and satisfy precise scaling laws between the average prompt luminosity, 〈Liso〉, and the luminosity at the end of the plateau, La, as functions of the time at the end of the plateau. All these features extend the applicability of the “cosmic candle” nature of Episode 3. The relevance of r-process in fulfilling the demanding scaling laws and the nested structure are indicated.

GRB 130427A and SN 2013cq: A Multi-wavelength Analysis of An Induced Gravitational Collapse Event

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.

GRB 140619B: a short GRB from a binary neutron star merger leading to black hole formation

Following the recent identification of the prototypical short GRB 090227B originating from a binary neutron star (NS) merger, leading to the formation of a black hole (BH), we present here a new example of such sources, GRB 140619B. The time-resolved spectral analysis performed on the Fermi-GBM data, allows for the identification of the characteristic features of the e + e - plasma at transparency (P-GRB) in the early 0:2 s of the GRB 140619B light curve: i.e., a thermal spectrum with an observed temperature kT = (324 33) keV which represents 40% of the total source fluence. The subsequent emission, with no evidence for a thermal spectrum, is identified with the prompt emission. We have consequently deduced a theoretical cosmological redshift of z = 2:67 0:37, a total burst energy E tot+e- = (6:03 0:79) 10 52 ergs, a baryon load B = (5:52 0:73) 10 -5 , and a Lorentz factor at transparency tr = (1:08 0:08) 10 4 . From the simulation of the prompt emission we have determined the average density of the circumburst medium (CBM),hnCBMi = (4:7 1:2) 10 -5 cm -3 , typical of the galactic halo environment. This low CBM density and the low baryon load, confirm the identification of the GRB progenitor as a NS‐NS merger. By assuming symmetric NS masses (MNS = 1:34 M ), the inferred baryon load corresponds to 3% of the total crustal mass, i.e. M2c = 7:26 10 -5 M . The corresponding emission of gravitational waves, in the inspiral phase up to the merger, corresponds to E T GW = 7:42 10 52 erg. We also show that the gravitational waves signal from the NS binary progenitor of GRB 140619B, in view of the large cosmological distance, is undetectable by the Advanced LIGO interferometer. Novel in this source is the presence of an observed emission at energies & 0:1 GeV lasting 5 s, with a total energy of ELAT = (2:02 0:52) 10 53 erg. We estimate the energy requirements of ELAT in terms of accretion of a fraction of M2c on the BH. From GRB 090227B and GRB 140619B, we have estimated the rate of such NS‐NS mergers, leading to BH formation, to be 0 = 1:7 +3:7 -1:4 10 -4 Gpc -3 yr -1 .

Induced gravitational collapse in the BATSE era: The case of GRB 970828

Following the recently established “Binary-driven HyperNova” (BdHN) model, we here interpret GRB 970828 in terms of the four episodes typical of such a model. The “Episode 1,” up to 40 s after the trigger time t0, with a time varying thermal emission and a total energy of Eiso,1st = 2.60 × 1053 erg, is interpreted as due to the onset of an hyper-critical accretion process onto a companion neutron star, triggered by the companion star, an FeCO core undergoing a SN explosion. The “Episode 2,” observed up t0 + 90 s, is interpreted as a canonical gamma ray burst, with an energy of

GRB 090510: A GENUINE SHORT GRB FROM A BINARY NEUTRON STAR COALESCING INTO A KERR–NEWMAN BLACK HOLE

E_{tot}^{e^ + e^ - } = 1.60 \times 10^{53}

Black holes, neutron stars and supernovae within the induced gravitational collapse paradigm for GRBs

erg, a baryon load of B = 7× 10-3 and a bulk Lorentz factor at transparency of G = 142.5. From this Episode 2, we infer that the GRB exploded in an environment with a large average particle density 〈n〉 ≈103 particles/cm3 and dense clouds characterized by typical dimensions of (4-8) × 1014 cm and δn/n ~ 10. The “Episode 3” is identified from t0 +90 s all the way up to 105-6 s: despite the paucity of the early X-ray data, typical in the BATSE, pre-Swift era, we find extremely significant data points in the late X-ray afterglow emission of GRB 970828, which corresponds to the ones observed in all BdHNe sources. The “Episode 4,” related to the Supernova emission, does not appear to be observable in this source, due to the presence of darkening from the large density of the GRB environment, also inferred from the analysis of the Episode 2.

GRB 140619B: a short GRB from a neutron star merger leading to the black hole formation

Context. The induced gravitational collapse (IGC) scenario has been introduced in order to explain the most energetic gamma ray bursts (GRBs), Eiso = 10 52 10 54 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 ( NS). 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.

Predicting supernova associated to gamma-ray burst 130427a

In a new classification of merging binary neutron stars (NSs) we separate short gamma-ray bursts (GRBs) in two sub-classes. The ones with