arXiv subjects

C. L. Bianco

Publications and source records attributed to C. L. Bianco.

At least 19 recordsLinked to original sources

arXiv2024

The long-short GRB connection

Long and short gamma-ray bursts (GRBs) are thought to arise from different and unrelated astrophysical progenitors. The association of long GRBs with supernovae (SNe) and the difference in the distributions of galactocentric offsets of long and short GRBs within their host galaxies have often been considered strong evidence of their unrelated origins. Long GRBs have been thought to result from the collapse of single massive stars, while short GRBs come from mergers of compact object binaries. Our present study challenges this conventional view. We demonstrate that the observational properties, such as the association with SNe and the different galactic offsets, are naturally explained within the framework of the binary-driven hypernova model, suggesting an evolutionary connection between long and short GRBs.

astro-ph.HE↗

arXiv2024

The role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole

The concept of the irreducible mass ($M_{\rm irr}$) has led to the mass-energy ($M$) formula of a Kerr black hole (BH), in turn leading to its surface area $S=16πM_{\rm irr}^2$. This also allowed the coeval identification of the reversible and irreversible transformations, soon followed by the concepts of "extracted" and "extractable" energy. This new conceptual framework avoids inconsistencies recently evidenced in a repetitive Penrose process. We consider repetitive decays in the ergosphere of an initially extreme Kerr BH and show the processes are highly irreversible. For each decay, the particle that the BH captures causes an increase of the irreducible mass (so the BH horizon), much larger than the extracted energy. The energy extraction process stops {when the BH reaches a positive spin lower limit set by the process boundary conditions}. Thus, the reaching of a final non-rotating Schwarzschild BH state through this accretion process is impossible. We have assessed such processes for selected decay radii and incoming particle with rest mass $1\%$ of the BH initial mass $M_0$. For $r= 1.2 M$ and $1.9 M$, the sequence stops after $8$ and $34$ decays, respectively, at a spin $0.991$ and $0.857$, the energy extracted has been only $1.16\%$, and $0.42\%$, the extractable energy is reduced by $17\%$ and $56\%$, and the irreducible mass increases by $5\%$ and $22\%$, all values in units of $M_0$. These results show the highly nonlinear change of the BH parameters, dictated by the BH mass-energy formula, and that the BH rotational energy is mainly converted into irreducible mass. Thus, evaluating the irreducible mass increase in any energy extraction processes in the Kerr BH ergosphere is mandatory.

gr-qc↗

arXiv2024

Ten Supernova-rise in Binary Driven Gamma-ray Bursts

The observation of a gamma-ray burst (GRB) associated with a supernova (SN) coincides remarkably with the energy output from a binary system comprising a very massive carbon-oxygen (CO) core and an associated binary neutron star (NS) by the Binary-Driven Hypernova (BdHN) model. The dragging effect in the late evolution of such systems leads to co-rotation, with binary periods on the order of minutes, resulting in a very fast rotating core and a binary NS companion at a distance of $\sim 10^5$ km. Such a fast-rotating CO core, stripped of its hydrogen and helium, undergoes gravitational collapse and, within a fraction of seconds, leads to a supernova (SN) and a newly born, fast-spinning neutron star ($ν$NS), we name the emergence of the SN and the $ν$NS as the SN-rise and $ν$NS-rise. Typically, the SN energies range from $10^{51}$ to $10^{53}$ erg. We address this issue by examining 10 cases of Type-I BdHNe, the most energetic ones, in which SN accretion onto the companion NS leads to the formation of a black hole (BH). In all ten cases, the energetics of the SN events are estimated, ranging between $0.18$ and $12 \times 10^{52}$ erg. Additionally, in all 8 sources at redshift $z$ closer than $4.61$, a clear thermal blackbody component has been identified, with temperatures between $6.2$ and $39.99$ keV, as a possible signature of pair-driven SN. The triggering of the X-ray afterglow induced by the $ν$NS-rise are identified in three cases at high redshift where early X-ray observations are achievable, benefits from the interplay of cosmological effects.

astro-ph.HE↗

arXiv2024

Probing electromagnetic-gravitational wave emission coincidence in type I binary-driven hypernova family of long GRBs at very-high redshift

The repointing time of the XRT instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within $\approx40$ s after a gamma-ray burst (GRB) trigger. To address this issue, we adopt a novel approach that capitalizes on the cosmological time dilation in GRBs with redshifts ranging from $3$ to $9$. Applying this strategy to Swift/XRT data, we investigate the earliest X-ray emissions of $368$ GRBs from the Swift catalog, including short and long GRBs. We compare the time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame (OTD) and the cosmological rest-frame (RTD). This technique is here used in the analysis of GRB 090423 at $z=8.233$ (RTD $\sim8.2$ s), GRB 090429B at $z\approx9.4$ (RTD $\sim10.1$ s), and GRB 220101A at $z=4.61$ (RTD $\sim14.4$ s). The cosmological time dilation enables us to observe the very early X-ray afterglow emission in these three GRBs. We thus validate the observation of the collapse of the carbon-oxygen (CO) core and the coeval newborn neutron star ($ν$NS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. We also evidence the $ν$NS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-optical-radio synchrotron afterglow emission. A brief gravitational wave signal may separate the two stages due to a fast-spinning $ν$NS triaxial-to-axisymmetric transition. We also analyze the long GRB redshift distribution for the different BdHN types and infer that BdHNe II and III may originate the NS binary progenitors of short GRBs.

astro-ph.HE↗

arXiv2023

GRB-SN Association within the Binary-Driven Hypernova Model

The observations of supernovae (SNe) Ic occurring after the prompt emission of long gamma-ray bursts (GRBs) are addressed within the binary-driven hypernova (BdHN) model where GRBs originate from a binary composed of a $\sim10M_\odot$ carbon-oxygen (CO) star and a neutron star (NS). The CO core collapse gives the trigger, leading to a hypernova with a fast-spinning newborn NS ($ν$NS) at its center. The evolution depends strongly on the binary period, $P_{\rm bin}$. For $P_{\rm bin}\sim5$min, BdHNe I occur with energies $10^{52}$--$10^{54}$erg. The accretion of SN ejecta onto the NS leads to its collapse, forming a black hole (BH) originating the MeV/GeV radiation. For $P_{\rm bin}\sim 10$min, BdHNe II occur with energies $10^{50}$--$10^{52}$erg and for $P_{\rm bin}\sim$hours, BdHN III occurs with energies below $10^{50}$erg. {In BdHNe II and III,} no BH is formed. The $1$--$1000$ms $ν$NS originates, in all BdHNe, the X-ray-optical-radio afterglows by synchrotron emission. The hypernova follows an independent evolution, becoming an SN Ic, powered by nickel decay, observable after the GRB prompt emission. We report $24$ SNe Ic associated with BdHNe. Their optical peak luminosity and time of occurrence are similar and independent of the associated GRBs. {From previously identified $380$ BdHN I comprising redshifts up to $z=8.2$, we analyze} four examples with their associated hypernovae. By multiwavelength extragalactic observations, we identify seven new Episodes, theoretically explained, fortunately not yet detected in galactic sources, opening new research areas. Refinement of population synthesis simulations is needed to map the progenitors of such short-lived binary systems inside our galaxy.

astro-ph.HE↗

arXiv2021

Nature of the ultrarelativistic prompt emission phase of GRB 190114C

We address the physical origin of the ultrarelativistic prompt emission (UPE) phase of GRB 190114C observed in the interval 1.9-3.99 s, by the Fermi-GBM in 10 keV-10 MeV . Thanks to high S/N ratio of Fermi-GBM data, a time resolved spectral analysis has evidenced a sequence of similar blackbody plus cutoff power-law spectra, on ever decreasing time intervals during the entire UPE phase. We assume that during the UPE phase, the inner engine of the GRB, composed of a Kerr black hole and a uniform test magnetic field B0, aligned with the BH rotation axis, operates in an overcritical field. We infer an $e^+e^-$ pair electromagnetic plasma in presence of a baryon load, a PEMB pulse, originating from a vacuum polarization quantum process in the inner engine. This initially optically thick plasma self-accelerates, giving rise at the transparency radius to the MeV radiation observed by Ferm-GBM. At trf > 3.99 s, the electric field becomes undercritical, and the inner engine operates in the classical electrodynamics regime and generate the GeV emission. During both the quantum and the classical electrodynamics processes, we determine the time varying mass and spin of the Kerr BH in the inner engine, fulfilling the Christodoulou-Hawking-Ruffini mass-energy formula. For the first time, we quantitatively show how the inner engine, by extracting the rotational energy of the Kerr BH, produces a series of PEMB pulses. We follow the quantum vacuum polarization process in sequences with decreasing time bins. We compute the Lorentz factors, the baryon loads and the radii at transparency, as well as the value of the magnetic field, assumed to be constant in each sequence. The fundamental hierarchical structure, linking the quantum electrodynamics regime to the classical electrodynamics regime, is characterized by the emission of blackholic quanta with a timescale $t=10^{-9}$s, and energy $E=10^{45}$ erg.

astro-ph.HE↗

arXiv2021

The morphology of the X-ray afterglows and of the jetted GeV emission in long GRBs

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 (CO$_{\rm core}$) and a neutron star (NS) companion. For binary periods $\sim 5$ min, the CO$_{\rm core}$ collapse originates the subclass BdHN I characterized by: 1) an energetic supernova (the "SN-rise"); 2) a black hole (BH), born from the NS collapse by SN matter accretion, leading to a GeV emission with luminosity $L_{\rm GeV} = A_{\rm GeV}\,t^{-α_{\rm GeV}}$, observed only in some cases; 3) a new NS ($ν$NS), born from the SN, originating the X-ray afterglow with $L_X = A_{\rm X}\,t^{-α_{\rm X}}$, observed in all BdHN I. We record $378$ sources and present for four prototypes GRBs 130427A, 160509A, 180720B and 190114C: 1) spectra, luminosities, SN-rise duration; 2) $A_X$, $α_X=1.48\pm 0.32$, and 3) the $ν$NS spin time-evolution. We infer a) $A_{\rm GeV}$, $α_{\rm GeV}=1.19 \pm 0.04$; b) the BdHN I morphology from time-resolved spectral analysis, three-dimensional simulations, and the GeV emission presence/absence in $54$ sources within the Fermi-LAT 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 $\approx 60^{\circ}$ from the normal to the orbital plane. We deduce BH masses $2.3$-$8.9~M_\odot$ and spin $0.27$-$0.87$ by explaining the GeV emission from the BH energy extraction, while their time evolution validates the BH mass-energy formula.

astro-ph.HE↗

arXiv2020

On the role of the Kerr-Newman black hole in the GeV emission of long gamma-ray bursts

X-ray Flashes (XRFs), binary-driven hypernovae (BdHNe) are long GRB subclasses with progenitor a CO$_{\rm core}$, undergoing a supernova (SN) explosion and hypercritically accreting in a tight binary system onto a companion neutron star (NS) or black hole (BH). In XRFs the NS does not reach by accretion the critical mass and no BH is formed. In BdHNe I, with shorter binary periods, the NS gravitationally collapses and leads to a new born BH. In BdHNe II the accretion on an already formed BH leads to a more massive BH. We assume that the GeV emission observed by \textit{Fermi}-LAT originates from the rotational energy of the BH. Consequently, we verify that, as expected, in XRFs no GeV emission is observed. In $16$ BdHNe I and $5$ BdHNe II, within the boresight angle of LAT, the integrated GeV emission allows to estimate the initial mass and spin of the BH. In the remaining $27$ sources in the plane of the binary system no GeV emission occurs, hampered by the presence of the HN ejecta. From the ratio, $21/48$, we infer a new asymmetric morphology for the BdHNe reminiscent of the one observed in active galactic nuclei (AGN): the GeV emission occurs within a cone of half-opening angle $\approx 60^{\circ}$ from the normal to the orbital plane of the binary progenitor. The transparency condition requires a Lorentz factor $Γ\sim 1500$ on the source of GeV emission. The GeV luminosity in the rest-frame of the source follows a universal power-law with index of $-1.20 \pm 0.04$, allowing to estimate the spin-down rate of the BH

astro-ph.HE↗

arXiv2019

On the GeV emission of the type I BdHN GRB 130427A

We propose that the "inner engine" of a type I binary-driven hypernova (BdHN) is composed of a Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field $B_0$ aligned with the BH rotation axis, and surrounded by an ionized plasma of extremely low density of $10^{-14}$~g~cm$^{-3}$. Using GRB 130427A as a prototype we show that this "inner engine" acts in a sequence of "elementary impulses". Electrons are accelerated to ultra-relativistic energy near the BH horizon and, propagating along the polar axis, $θ=0$, they can reach energies of $\sim 10^{18}$ eV, and partially contribute to ultra-high energy cosmic rays (UHECRs). When propagating with ${θ\neq 0}$ through the magnetic field $B_0$ they give origin by synchrotron emission to GeV and TeV radiation. The mass of BH, $M=2.3 M_\odot$, its spin, $α= 0.47$, and the value of magnetic field $B_0= 3.48 \times 10^{10}$ G, are determined self-consistently in order to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${\cal E} \sim 10^{37}$ erg, is $\sim 10^{-14}$ s at the beginning of the process, then slowly increasing with time evolution. In principle, this "\textit{inner engine}" can operate in a GRB for thousands of years. By scaling the BH mass and the magnetic field the same "inner engine" can describe active galactic nuclei (AGN).

astro-ph.HE↗

arXiv2019

The inner engine of GeV-radiation-emitting gamma-ray bursts

We motivate how the most recent progress in the understanding the nature of the GeV radiation in most energetic gamma-ray bursts (GRBs), the binary-driven hypernovae (BdHNe), has led to the solution of a forty years unsolved problem in relativistic astrophysics: how to extract the rotational energy from a Kerr black hole for powering synchrotron emission and ultra high-energy cosmic rays. The "inner engine" is identified in the proper use of a classical solution introduced by Wald in 1974 duly extended to the most extreme conditions found around the newborn black hole in a BdHN. The energy extraction process occurs in a sequence impulsive processes each accelerating protons to $10^{21}$ eV in a timescale of $10^{-6}$ s and in presence of an external magnetic field of $10^{14}$ G. Specific example is given for a black hole of initial angular momentum $J=0.3\,M^2$ and mass $M\approx 3\,M_\odot$ leading to the GeV radiation of $10^{49}$ erg$\cdot$s$^{-1}$. The process can energetically continue for thousands of years.

astro-ph.HE↗

arXiv2019

Self-similarity and power-laws in GRB 190114C

Following Fermi and NOT observations, Ruffini et al. (2019b) soon identified GRB 190114C as BdHN I at z=0.424, it has been observed since, with unprecedented accuracy, [...] all the way to the successful optical observation of our predicted supernova (SN). This GRB is a twin of GRB 130427A. Here we take advantage of the GBM data and identify in it three different Episodes. Episode 1 represents the precursor which includes the SN breakout and the creation of the new neutron star ($ν$NS), the hypercritical accretion of the SN ejecta onto the NS binary companion, exceeding the NS critical mass at $t_{rf}=1.9$s. Episode 2 starting at $t_{rf}=1.9$s includes three major events: the formation of the BH, the onset of the GeV emission and the onset of the ultra-relativistic prompt emission (UPE), which extends all the way up to $t_{rf}=3.99$s. Episode 3 which occurs at times following $t_{rf}=3.99$s reveals the presence of a cavity carved out in the SN ejecta by the BH formation. We perform an in depth time-resolved spectral analysis on the entire UPE with the corresponding determination of the spectra best fit by a cut-off power-law and a black body (CPL+BB) model, and then we repeat the spectral analysis in 5 successive time iterations in increasingly shorter time bins: we find a similarity in the spectra in each stage of the iteration revealing clearly a self-similar structure. We find a power-law dependence of the BB temperature with index $-1.56\pm0.38$, a dependence with index $-1.20\pm0.26$ for the gamma-ray luminosity confirming a similar dependence with index $-1.20\pm0.36$ which we find as well in the GeV luminosity, both expressed in the rest-frame. We thus discover in the realm of relativistic astrophysics the existence of a self-similar physical process and power-law dependencies, extensively described in the micro-physical world by the classical works of Heisenberg-Landau-Wilson.

astro-ph.HE↗

arXiv2019

Electromagnetic emission of white dwarf binary mergers

It has been recently proposed that the ejected matter from white dwarf (WD) binary mergers can produce transient, optical and infrared emission similar to the "kilonovae" of neutron star (NS) binary mergers. To confirm this we calculate the electromagnetic emission from WD-WD mergers and compare with kilonova observations. We simulate WD-WD mergers leading to a massive, fast rotating, highly magnetized WD with an adapted version of the smoothed-particle-hydrodynamics (SPH) code Phantom. We thus obtain initial conditions for the ejecta such as escape velocity, mass and initial position and distribution. The subsequent thermal and dynamical evolution of the ejecta is obtained by integrating the energy-conservation equation accounting for expansion cooling and a heating source given by the fallback accretion onto the newly-formed WD and its magneto-dipole radiation. We show that magnetospheric processes in the merger can lead to a prompt, short gamma-ray emission of up to $\approx 10^{46}$ erg in a timescale of $0.1$-$1$ s. The bulk of the ejecta initially expands non-relativistically with velocity $0.01 c$ and then it accelerates to $0.1 c$ due to the injection of fallback accretion energy. The ejecta become transparent at optical wavelengths around $\sim 7$ days post-merger with a luminosity $10^{41}$-$10^{42}$ erg s$^{-1}$. The X-ray emission from the fallback accretion becomes visible around $\sim 150$-$200$ day post-merger with a luminosity of $10^{39}$ erg s$^{-1}$. We also predict the post-merger time at which the central WD should appear as a pulsar depending on the value of the magnetic field and rotation period.

astro-ph.HE↗

arXiv2018

On the ultra-relativistic Prompt Emission (UPE), the Hard and Soft X-ray Flares, and the extended thermal emission (ETE) in GRB 151027A

We analyze GRB 151027A within the binary-driven hypernova (BdHN) approach, with progenitor a carbon-oxygen core on the verge of a supernova (SN) explosion and a binary companion neutron star (NS). The hypercritical accretion of the SN ejecta onto the NS leads to its gravitational collapse into a black hole (BH), to the emission of the GRB and to a copious $e^+e^-$ plasma. The impact of this $e^+e^-$ plasma on the SN ejecta explains {the} early soft X-ray flare observed in long GRBs. We here apply this approach to the UPE and to the hard X-ray flares. We use GRB 151027A as a prototype. From the time-integrated and the time-resolved analysis we identify a double component in the UPE and confirm its ultra-relativistic nature. We confirm the mildly-relativistic nature of the soft X-ray flare, of the hard X-ray flare and of the ETE. We show that the ETE identifies the transition from a SN to the HN. We then address the theoretical justification of these observations by integrating the hydrodynamical propagation equations of the $e^+ e^-$ into the SN ejecta, the latter independently obtained from 3D smoothed-particle-hydrodynamics simulations. We conclude that the UPE, the hard X-ray flare and the soft X-ray flare do not form a causally connected sequence: Within our model they are the manifestation of \textbf{the same} physical process of the BH formation as seen through different viewing angles, implied by the morphology and the $\sim 300$~s rotation period of the HN ejecta.

astro-ph.HE↗

arXiv2018

On a GRB afterglow model consistent with hypernovae observations

We describe the afterglows of the long gamma-ray-burst (GRB) 130427A within the context of a binary-driven hypernova (BdHN). The afterglows originate from the interaction between a newly born neutron star ($ν$NS), created by an Ic supernova (SN), and a mildly relativistic ejecta of a hypernova (HN). Such a HN in turn results from the impact of the GRB on the original SN Ic. The mildly relativistic expansion velocity of the afterglow ($Γ\sim 3$) is determined, using our model independent approach, from the thermal emission between $196$~s and $461$~s. The power-law in the optical and X-ray bands of the afterglow is shown to arise from the synchrotron emission of relativistic electrons in the expanding magnetized HN ejecta. Two components contribute to the injected energy: the kinetic energy of the mildly relativistic expanding HN and the rotational energy of the fast rotating highly magnetized $ν$NS. We reproduce the afterglow in all wavelengths from the optical ($10^{14}$~Hz) to the X-ray band ($10^{19}$~Hz) over times from $604$~s to $5.18\times 10^6$~s relative to the Fermi-GBM trigger. Initially, the emission is dominated by the loss of kinetic energy of the HN component. After $10^5$~s the emission is dominated by the loss of rotational energy of the $ν$NS, for which we adopt an initial rotation period of $2$~ms and a dipole plus quadrupole magnetic field of $\lesssim \! 7\times 10^{12}$~G or $\sim \! 10^{14}$~G. This scenario with a progenitor composed of a CO$_{\rm core}$ and a NS companion differs from the traditional ultra-relativistic-jetted treatments of the afterglows originating from a single black hole.

astro-ph.HE↗

arXiv2018

GRB 170817A-GW170817-AT 2017gfo and the observations of NS-NS, NS-WD and WD-WD mergers

The LIGO-Virgo Collaboration has announced the detection of GW170817 and has associated it with GRB 170817A. These signals have been followed after 11 hours by the optical and infrared emission of AT 2017gfo. The origin of this complex phenomenon has been attributed to a neutron star-neutron star (NS-NS) merger. In order to probe this association we confront our current understanding of the gravitational waves and associated electromagnetic radiation with four observed GRBs originating in binaries composed of different combinations NSs and white dwarfs (WDs). We consider 1) GRB 090510 the prototype of NS-NS merger leading to a black hole (BH); 2) GRB 130603B the prototype of a NS-NS merger leading to massive NS (MNS) with an associated kilonova; 3) GRB 060614 the prototype of a NS-WD merger leading to a MNS with an associated kilonova candidate; 4) GRB 170817A the prototype of a WD-WD merger leading to massive WD with an associated AT 2017gfo-like emission. None of these systems support the above mentioned association. The clear association between GRB 170817A and AT 2017gfo has led to introduce a new model based on on a new subfamily of GRBs originating from WD-WD mergers. We show how this novel model is in agreement with the exceptional observations in the optical, infrared, X- and gamma-rays of GRB 170817A-AT 2017gfo.

astro-ph.HE↗

arXiv2018

On the Short GRB GeV emission from a Kerr Black hole

It has recently become clear that in both short and long gamma-ray bursts (GRBs) it coexists a sequence of different events, each characterized by specific physical processes and corresponding values of the Lorentz gamma factors. The ultra-relativistic prompt emission (UPE) phase, with Lorentz factor $Γ\leq10^4$, is followed by a mildly relativistic plateau-afterglow phase with $Γ\lesssim2$. The GeV radiation, with $Γ\lesssim50$, coexists with the above two phases. It is shown that: a) the GeV radiation originates at the onset of the formation of a black hole (BH), b) its luminosity follows specific power-law dependence when measured in the rest frame of the source with a decay index $γ=-1.29\pm0.06$ in the case of the short GRBs, and $γ=-1.20\pm0.04$ in the case of the long GRBs, c) these energetics requirements are used to derive the mass and spin of the BH originating this extended GeV emission. We present these conceptual results for the case of short GRBs in this article and give the extended analysis for long GRBs in a companion article. A direct astrophysical application of these results is that the merger of binary neutron stars leading to BH formation emits GeV radiation: the GeV emission is a necessary and sufficient condition to indicate the creation of a BH in S-GRBs.

astro-ph.HE↗

arXiv2018

On the rate and on the gravitational wave emission of short and long GRBs

On the ground of the large number of gamma-ray bursts (GRBs) detected with cosmological redshift, we classified GRBs in seven subclasses, all with binary progenitors originating gravitational waves (GWs). Each binary is composed by combinations of carbon-oxygen cores (CO$_{\rm core}$), neutron stars (NSs), black holes (BHs) and white dwarfs (WDs). The long bursts, traditionally assumed to originate from a BH with an ultra-relativistic jetted emission, not emitting GWs, have been subclassified as (I) X-ray flashes (XRFs), (II) binary-driven hypernovae (BdHNe), and (III) BH-supernovae (BH-SNe). They are framed within the induced gravitational collapse (IGC) paradigm with progenitor a CO$_{\rm core}$-NS/BH binary. The supernova (SN) explosion of the CO$_{\rm core}$ triggers an accretion process onto the NS/BH. If the accretion does not lead the NS to its critical mass, an XRF occurs, while when the BH is present or formed by accretion, a BdHN occurs. When the binaries are not disrupted, XRFs lead to NS-NS and BdHNe lead to NS-BH. The short bursts, originating in NS-NS, are subclassified as (IV) short gamma-ray flashes (S-GRFs) and (V) short GRBs (S-GRBs), the latter when a BH is formed. There are (VI) ultra-short GRBs (U-GRBs) and (VII) gamma-ray flashes (GRFs), respectively formed in NS-BH and NS-WD. We use the occurrence rate and GW emission of these subclasses to assess their detectability by Advanced LIGO-Virgo, eLISA, and resonant bars. We discuss the consequences of our results in view of the announcement of the LIGO-Virgo Collaboration of the source GW 170817 as being originated by a NS-NS.

astro-ph.HE↗

arXiv2017

Early X-ray Flares in GRBs

We analyze the early X-ray flares in the GRB "flare-plateau-afterglow" (FPA) phase observed by Swift-XRT. The FPA occurs only in one of the seven GRB subclasses: the binary-driven hypernovae (BdHNe). This subclass consists of long GRBs with a carbon-oxygen core and a neutron star (NS) binary companion as progenitors. The hypercritical accretion of the supernova (SN) ejecta onto the NS can lead to the gravitational collapse of the NS into a black hole. Consequently, one can observe a GRB emission with isotropic energy $E_{iso}\gtrsim10^{52}$~erg, as well as the associated GeV emission and the FPA phase. Previous work had shown that gamma-ray spikes in the prompt emission occur at $\sim 10^{15}$--$10^{17}$~cm with Lorentz gamma factor $Γ\sim10^{2}$--$10^{3}$. Using a novel data analysis we show that the time of occurrence, duration, luminosity and total energy of the X-ray flares correlate with $E_{iso}$. A crucial feature is the observation of thermal emission in the X-ray flares that we show occurs at radii $\sim10^{12}$~cm with $Γ\lesssim 4$. These model independent observations cannot be explained by the "fireball" model, which postulates synchrotron and inverse Compton radiation from a single ultra relativistic jetted emission extending from the prompt to the late afterglow and GeV emission phases. We show that in BdHNe a collision between the GRB and the SN ejecta occurs at $\simeq10^{10}$~cm reaching transparency at $\sim10^{12}$~cm with $Γ\lesssim4$. The agreement between the thermal emission observations and these theoretically derived values validates our model and opens the possibility of testing each BdHN episode with the corresponding Lorentz gamma factor.

astro-ph.HE↗