Within the binary-driven hypernova I (BdHN I) scenario, the gamma-ray burst GRB190114C originates in a binary system composed of a massive carbon-oxygen core (COcore), and a binary neutron star (NS) ...companion. As the COcore undergoes a supernova explosion with the creation of a new neutron star ( NS), hypercritical accretion occurs on the companion binary neutron star until it exceeds the critical mass for gravitational collapse. The formation of a black hole (BH) captures 1057 baryons by enclosing them within its horizon, and thus a cavity of approximately 1011 cm is formed around it with initial density 10−7 g cm−3. A further depletion of baryons in the cavity originates from the expansion of the electron-positron-photon (e+e−γ) plasma formed at the collapse, reaching a density of 10−14 g cm−3 by the end of the interaction. It is demonstrated here using an analytical model complemented by a hydrodynamical numerical simulation that part of the e+e−γ plasma is reflected off the walls of the cavity. The consequent outflow and its observed properties are shown to coincide with the featureless emission occurring in a time interval of duration trf, measured in the rest frame of the source, between 11 and 20 s of the GBM observation. Moreover, similar features of the GRB light curve were previously observed in GRB 090926A and GRB 130427A, all belonging to the BdHN I class. This interpretation supports the general conceptual framework presented in R. Ruffini et al. and guarantees that a low baryon density is reached in the cavity, a necessary condition for the operation of the "inner engine" of the GRB presented in an accompanying article.
Abstract
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 ∼10
M
⊙
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
bin
. For
P
bin
∼ 5 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
bin
∼ 10 min, BdHNe II occur with energies 10
50
–10
52
erg and for
P
bin
∼ hours, BdHNe III occur 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.
Abstract The repointing time of the X-Ray Telescope (XRT) instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within ...≈40 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 observed time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame, and the corresponding cosmological rest-frame time delay (RTD). This technique is here used in the analysis of GRB 090423 at z = 8.233 (RTD ∼8.2 s), GRB 090429B at z ≈ 9.4 (RTD ∼10.1 s), and GRB 220101A at z = 4.61 (RTD ∼14.4 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 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-ray/optical/radio synchrotron afterglow emission. A brief gravitational-wave signal may separate the two stages owing 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.
We propose that the inner engine of a type I binary-driven hypernova (BdHN) is composed of Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field B0 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 accelerate to ultrarelativistic energy near the BH horizon, propagating along the polar axis, θ = 0, where they can reach energies of ∼1018 eV, partially contributing to ultrahigh-energy cosmic rays. When propagating with through the magnetic field B0, they produce GeV and TeV radiation through synchroton emission. The mass of BH, M = 2.31M , its spin, = 0.47, and the value of magnetic field B0 = 3.48 × 1010 G, are determined self consistently to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy erg is ∼10−14 s at the beginning of the process, then slowly increases with time evolution. In principle, this "inner engine" can operate in a gamma-ray burst (GRB) for thousands of years. By scaling the BH mass and the magnetic field, the same inner engine can describe active galactic nuclei.
ABSTRACT There is mounting evidence for the binary nature of the progenitors of gamma-ray bursts (GRBs). For a long GRB, the induced gravitational collapse paradigm proposes as progenitor, or ..."in-state," a tight binary system composed of a carbon-oxygen core (CO ) undergoing a supernova explosion that triggers hypercritical accretion onto a neutron star (NS) companion. For a short GRB (S-GRB), an NS-NS merger is traditionally adopted as the progenitor. We divide long and S-GRBs into two subclasses, depending on whether or not a black hole (BH) is formed in the merger or in the hypercritical accretion process exceeding the NS critical mass. For long bursts, when no BH is formed, we have the subclass of X-ray flashes (XRFs), with isotropic energy erg and rest-frame spectral peak energy . When a BH is formed, we have the subclass of binary-driven hypernovae (BdHNe), with erg and . In analogy, short bursts are similarly divided into two subclasses. When no BH is formed, short gamma-ray flashes (S-GRFs) occur, with erg and . When a BH is formed, the authentic S-GRBs occur, with erg and . We give examples and observational signatures of these four subclasses and their rate of occurrence. From their respective rates it is possible that "in-states" of S-GRFs and S-GRBs originate from the "out-states" of XRFs. We indicate two additional progenitor systems: white dwarf-NS and BH-NS. These systems have hybrid features between long and short bursts. In the case of S-GRBs and BdHNe evidence is given of the coincidence of the onset of the high-energy GeV emission with the birth of a Kerr BH.
A novel concept has recently been proposed for explaining the temporal coincidence of some gamma ray bursts (GRBs) with an associated supernova (SN) in terms of the gravitational collapse of a ...neutron star (NS) onto a black hole (BH), induced by a type Ib/c SN explosion. We applied these considerations to the exceptional case of GRB 090618, for which there is evidence of an SN ~ 10 days after the GRB occurrence. We calculated the accretion rate and total accreted mass onto an NS from an SN Ib/c that originated from a companion evolved star. These calculations show that the NS reaches the critical mass in a few seconds and undergoes gravitational collapse onto a BH, leading to the emission of a GRB. We find for the mass of the NS companion, MNS, and for the SN core progenitor, Mcore, the following mass ranges: 1.8 ≲ MNS/M⊙ ≲ 2.1 and 3 ≤ Mcore/M⊙ ≤ 8. Finally, we discuss the complementarity of these considerations to alternative processes explaining long and short GRBs.
Abstract
GRB 190829A is the fourth-closest gamma-ray burst to date (
z
= 0.0785). Owing to its wide range of radio, optical, X-ray, and very-high-energy observations by HESS, it has become an ...essential new source that has been examined by various models with complementary approaches. Here, we show in GRB 190829A that the double prompt pulses and the three multiwavelength afterglows are consistent with the type II binary-driven hypernova model. The progenitor is a binary composed of a carbon–oxygen (CO) star and a neutron star (NS) companion. The gravitational collapse of the iron core of the CO star produces a supernova (SN) explosion and leaves behind a new NS (
ν
NS) at its center. The accretion of the SN ejecta onto the NS companion and onto the
ν
NS via matter fallback spins up the NSs and produces the double-peak prompt emission. The synchrotron emission from the expanding SN ejecta, with energy injection from the rapidly spinning
ν
NS and its subsequent spindown, leads to the afterglow in the radio, optical, and X-ray bands. We model the sequence of physical and related radiation processes in BdHNe, and focus on individuating the binary properties that play the relevant roles.
We consider crossed electric and a magnetic fields (B→=Bzˆ,E→=Eyˆ), with E/B<1, in presence of some initial number of e± pairs. We do not discuss here the mechanism of generation of these initial ...pairs. The electric field accelerates the pairs to high-energies thereby radiating high-energy synchrotron photons. These photons interact with the magnetic field via magnetic pair production process (MPP), i.e. γ+B→e++e−, producing additional pairs. We here show that the motion of all the pairs around the magnetic field lines generates a current that induces a magnetic field that shields the initial one. For instance, for an initial number of pairs N±,0=1010, an initial magnetic field of 1012 G can be reduced of a few percent. The screening occurs in the short timescales 10−21≤t≤10−15 s, i.e. before the particle acceleration timescale equals the synchrotron cooling timescale. The present simplified model indicates the physical conditions leading to the screening of strong magnetic fields. To assess the occurrence of this phenomenon in specific astrophysical sources, e.g. pulsars or gamma-ray bursts, the model can be extended to evaluate different geometries of the electric and magnetic fields, quantum effects in overcritical fields, and specific mechanisms for the production, distribution, and multiplicity of the e−e+ pairs.
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