From the 3 November to the 8 December 2018, 2 Iranian students from Shiraz University visited ICRANet center in Pescara, in the framework of the Memorandum of Understanding between the two Institutions: Mrs Somayyeh Mahmoudikooshkeqazi and Saeidehalsadat Modaresvamegh. During their visit, the students had the opportunity to discuss their scientific research and to have fruitful exchange of ideas with other ICRANet researchers from different parts of the world.

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J. A. Rueda, R. Ruffini, L. M. Becerra, C. L. Fryer, Simulating the induced gravitational collapse scenario of long gamma-ray bursts, International Journal of Modern Physics A, Volume 33, Issue 31, id. 1844031 (2018), published on 19 November 2018.

We present the state-of-the-art of the numerical simulations of the supernova (SN) explosion of a carbon-oxygen core (COcore) that forms a compact binary with a neutron star (NS) companion, following the induced gravitational collapse (IGC) scenario of long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). We focus on the consequences of the hypercritical accretion of the SN ejecta onto the NS companion which either becomes a more massive NS or gravitationally collapses forming a black hole (BH). We summarize the series of results on this topic starting from the first analytic estimates in 2012 all the way up to the most recent three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) numerical simulations in 2018. We present a new SN ejecta morphology, highly asymmetric, acquired by binary interaction and leading to well-defined, observable signatures in the gamma- and X-rays emission of long GRBs.

Link:https://www.worldscientific.com/doi/abs/10.1142/S0217751X18440311


M. A. Prakapenia, I. A. Siutsou, G. V. Vereshchagin, Thermalization of electron–positron plasma with quantum degeneracy, Physics Letters A, available online from 25 October 2018, in press.
The non-equilibrium electron–positron–photon plasma thermalization process is studied using relativistic Boltzmann solver, taking into account quantum corrections both in non-relativistic and relativistic cases. Collision integrals are computed from exact QED matrix elements for all binary and triple interactions in the plasma. It is shown that in non-relativistic case (temperatures kBT ≤ 0.3 mec2) binary interaction rates dominate over triple ones, resulting in establishment of the kinetic equilibrium prior to final relaxation towards the thermal equilibrium, in agreement with the previous studies. On the contrary, in relativistic case (final temperatures kBT ≥ 0.3 mec2) triple interaction rates are fast enough to prevent the establishment of kinetic equilibrium. It is shown that thermalization process strongly depends on quantum degeneracy in initial state, but does not depend on plasma composition.

Link: https://www.sciencedirect.com/science/article/abs/pii/S0375960118310594


Ruffini, R.; Becerra, L.; Bianco, C. L.; Chen, Y. C.; Karlica, M.; Kovacevic, M.; Melon Fuksman, J. D.; Moradi, R.; Muccino, M.; Pisani, G. B.; Primorac, D.; Rueda, J. A.; Vereshchagin, G. V.; Wang, Y.; Xue, S.-S., On the ultra-relativistic Prompt Emission (UPE), the Hard and Soft X-ray Flares, and the extended thermal emission (ETE) in GRB 151027A, accepted for publication in The Astrophysical Journal on 3 November 2018.

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 the same physical process of the BH formation as seen through different viewing angles, implied by the morphology and the ∼300s rotation period of the HN ejecta.

Link: https://arxiv.org/abs/1712.05001


Ruffini, R.; Karlica, M.; Sahakyan, N.; Rueda, J. A.; Wang, Y.; Mathews, G. J.; Bianco, C. L.; Muccino, M., On a GRB afterglow model consistent with hypernovae observations, accepted for publication in The Astrophysical Journal on 21 October 2018.

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 (νNS), 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∼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 νNS. We reproduce the afterglow in all wavelengths from the optical (1014Hz) to the X-ray band (1019Hz) over times from 604s to 5.18×106 s relative to the Fermi-GBM trigger. Initially, the emission is dominated by the loss of kinetic energy of the HN component. After 105 s the emission is dominated by the loss of rotational energy of the νNS, for which we adopt an initial rotation period of 2~ms and a dipole plus quadrupole magnetic field of ≲7×1012G or ∼1014 G. This scenario with a progenitor composed of a COcore and a NS companion differs from the traditional ultra-relativistic-jetted treatments of the afterglows originating from a single black hole.

Link: https://arxiv.org/abs/1712.05000