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ICRANet Newsletter



ICRANet Newsletter
Ottobre – Novembre 2018






1. A GRB afterglow model consistent with hypernovae observations

The paper with this title co-authored by R. Ruffini, M. Karlica, N. Sahakyan, J.A. Rueda, Y. Wang, G.J. Mathews, C.L. Bianco and M. Muccino has been accepted for publication by the Astrophysical Journal (ApJ) on October 21, 2018.

In this paper our group presents an important paradigm shift in contrast to the traditional ultrarelativistic external shock scenario of the GRB afterglows which can be found in most of traditional literature. For our first investigation we used data of famous GRB 130427A with time resolved afterglow observations from radio till GeV band in timeframe from 604 till 5184000 seconds after the trigger. From model independent measurements for GRB 130427A of thermal emission expansion from 196 till 461 seconds after trigger with inferred velocity v/c~0.95 and corresponding Lorentz factor Γ~3 which decays after 16.7 days toward v/c~0.1 based of FeII 5169 measurements it was clear that the traditional ultrarelativistic scenario could not be used for description of afterglow.

Another novelty of this paper is the build up of synchrotron radiation within hypernova ejecta magnetized by the newly born neutron star as expected by the BdHN model of long GRBs. Following the geometry and strength of the newly born pulsar’s magnetic field together with the mildly relativistic expansion of hypernova ejecta it was possible to asses and solve the kinetic equation for radiating electrons giving us the spectral evolution of synchrotron radiation which fit genuinely well with observed time resolved spectra of GRB 130427A as shown on figure 1.

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Fig. 1. Model evolution (lines) of synchrotron spectral luminosity at various times compared with measurements (points with error bars) in various spectral bands for GRB 130724A.


Analysis presented in this paper goes more in line with the long GRB-SN connection cause all of the known supernovae associated with long GRBs, among them SN 2013cq associated with GRB 130427A, are broad lined type Ic supernovae indicating a binary system progenitor what is also expected by BdHN GRB model. Also it stresses the importance of model independent expansion velocity measurements of GRBs in afterglow phase which are an crucial ingredient in understanding of the astrophysical system and their subsequent theoretical treatment.

The paper is available here: https://arxiv.org/abs/1712.05000





2. Accordo di Collaborazione ICRANet - Università Campus Bio-Medico di Roma, 11 Ottobre 2018


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La cerimonia ufficiale tenutasi il 14 Novembre presso la sede dell’Università Campus Bio-Medico. Da sinistra a destra: la Prof.ssa Simonetta Filippi, il Presidente Raffaele Calabrò, il Dr Benedetto Marino, il Prof. Marco Tavani, il Prof. Remo Ruffini, il Prof. Paolo Giommi e il Prof. Christian Cherubini.


L’ 11 Ottobre 2018, l’ICRANet ha siglato un Accordo di Collaborazione con l’Università Campus Bio-Medico di Roma (Italia), che sarà valido per 2 anni. Il documento ufficiale è stato firmato dal Prof. Raffaele Calabrò (Presidente) e dal Dr Andrea Rossi (Direttore Generale) per l’Università Campus Bio-Medico, e dal Prof. Ruffini, Direttore ICRANet.

Per celebrare la firma dell’accordo, l’Università Campus Bio-Medico ha organizzato una cerimonia ufficiale presso la propria sede a Roma, il giorno Mercoledì 14 Novembre 2018, alla presenza del Prof. Ruffini, del Prof. Raffaele Calabrò, della Prof.ssa Simonetta Filippi (Campus Bio-Medico), del Prof. Christian Cherubini (Campus Bio-Medico), del Prof. Paolo Giommi (ASI), del Prof. Marco Tavani (INAF) e del Dr. Benedetto Marino.

Le principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell’Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l’organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshops, e il lavoro congiunto per le pubblicazioni scientifiche.

Per consultare il testo dell’accordo:
http://www.icranet.org/documents/agreementICRANet-CampusBiomedico.pdf



3. 13th Meeting del Marie Skłodowska-Curie actions’ Advisory Group, Bruxelles, 7 Novembre 2018

Il 7 Novembre 2018, il Professor Ruffini ha partecipato al 13 th Meeting del MSCA Advisory Group a Bruxelles. Il MSCA supporta finanziariamente ricercatori a tutti i livelli della loro carriera, indipendentemente dalla loro nazionalità e disciplina. I finanziamenti possono essere attribuiti a ricercatori individuali, networks, staff exchange programmes e doctoral/postdoctoral programmes. Inoltre, il MSCA permette agli scienziati di fare esperienza alivello internazionale, intersettoriale e interdisciplinare, e di completare il loro training scientifico con competenze trasversali che possono aumentare la loro impiegabilità e le loro prospettive lavorative. Durante il meeting, l’ Horizon 2020 (H2020) Advisory Group del Marie Skłodowska Curie Actions ha lavorato alla preparazione di un report focalizzato sulla parte relativa al 2020 dell’ H2020 Working Programme (WP) per il periodo 2018-2020. Un report più completo ed esaustivo sarà preparato il prossimo anno.

Per maggiori informazioni sul MSCA Advisory Group:
http://ec.europa.eu/research/mariecurieactions/




4. UNOOSA High Level Forum: The way forward after UNISPACE+50 and on Space2030, Bonn, Germania 13 - 16 Novembre 2018


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Foto di gruppo dell'UNOOSA High Level Forum a Bonn, Germania


Dal 13 al 16 Novembre 2018, il Professor Ruffini, Direttore ICRANet, ha partecipato all’ High Level Forum “The way forward after UNISPACE+50 and on Space2030”, organizzato dall’ufficio delle Nazioni Unite per gli affari dello spazio extra-atmosferico (UNOOSA) e dall’Amministrazione Spaziale Tedesca (DLR). Questo High Level Forum è stata un’importante piattaforma per fornire aggiornamenti e raccomandazioni in merito alla potenzialità delle innovazioni spaziali per affrontare le nuove ed emergenti sfide dello sviluppo sostenibile. Come primo High Level Forum dopo UNISPACE+50, questo meeting ha dato la possibilità di discutere dei risultati di UNISPACE+50, attraverso una sessione di 2 giorni sulle tematiche prioritarie, seguita da 2 giorni di discussione incentrata sui 4 pilastri: Space Diplomacy, Space Society, Space Economy e Space Accessibility. Nel corso del meeting, il Professor Ruffini ha presentato un poster dal titolo “The Role of Space Sciences for Relativistic Astrophysics in the knowledge of our Universe”, per presentare al pubblico gli ultimi risultati scientifici raggiunti dai ricercatori dell’ICRANet.


5. Bando congiunto “BRFFR – ICRANet – 2018”


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A Novembre 2018, la Belarusian Republican Foundation for Fundamental Research (BRFFR) e ICRANet hanno annunciato la pubblicazione di un bando congiunto per progetti di ricerca di base comune, in astrofisica relativistica. Le aree scientifiche interessate dal bando sono l’astrofisica relativistica, la cosmologia e la gravitazione. Le applications congiunte da team di ricerca internazionali, inclusi gli scienziati bielorussi, devono essere presentate simultaneamente, utilizzando l’application form concordata da entrambe le organizzazioni: gli scienziati bielorussi applicano per il BRFFR, quelli internazionali per ICRANet. La durata del progetto è di circa 2 anni, e la scadenza per la presentazione delle domande è il 14 Dicembre 2018.

Per maggiori informazioni sul bando e per scaricare l’application form:
http://www.icranet.org/index.php?option=com_content&task=view&id=1218

Informazioni più dettagliate per i ricercatori bielorussi, sono disponibili sul sito web del BRFFR (in russo):
http://fond.bas-net.by/if264.html.

Informazioni più dettagliate per chi applica per ICRANet:
http://www.icranet.org/documents/general_terms.pdf




6. Visite scientifiche presso il centro ICRANet di Pescara


Somayyeh   Saeideh
Somayyeh Mahmoudikooshkeqazi e Saeidehalsadat Modaresvamegh.

Dal 3 Novembre all’ 8 Dicembre 2018, 2 studentesse iraniane della Shiraz University, hanno visitato il centro ICRANet di Pescara, nel quadro del Memorandum of Understanding tra i due istituti: Somayyeh Mahmoudikooshkeqazi e Saeidehalsadat Modaresvamegh. Durante la loro visita, hanno avuto l’opportunità di discutere le loro ricerche scientifiche e di avere interessanti scambi con gli altri ricercatori dell’ICRANet e da diverse parti del mondo.


7. Pubblicazioni recenti

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

 
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