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2020
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ICRANet Boletim informativo
Abril – Maio de 2020



SUMÁRIO
1. COVID-19: Estatísticas
2. Magnetic field and rotation of the newborn neutron star in binary-driven hypernovae inferred from the X-ray afterglow of long gamma-ray bursts
3. O governo da Armênia atribui um bolsa de Doutorado à ICRANet-Armênia, 21 de maio de 2020
4. “Gerbertus 2020 – Scientific Rationale”, podcast meeting, 7 de maio de 2020 (em inglês)
5. Webinar COVID, Tucson, EUA, 19 de maio de 2020
6. O Quarto Encontro Zeldovich torna-se virtual
7. Convite à apresentação de propostasconjuntas “BRFFR – ICRANet 2020”
8. Últimas publicações
9. Avaliação interna do artigo do Dr Liang Li “Thermal Components in Gamma-Ray Bursts. II. Constraining the Hybrid Jet Model” publicado em ApJS
10. Avaliação interna do artigo em co-autoria do Prof. Shesheng Xue “Supercritically charged objects and electron-positron pair creation” publicado na revista Physical Review D



1. COVID-19: Estatísticas

1 A partir de 15 de abril de 2020, a ICRANet disponibiliza seus relatórios diários sobre o COVID-19. Acesse o seguinte link na página da ICRANet: http://www.icranet.org/covid19-statistics.
A função logística fenomenológica é usada para modelar a evolução da pandemia do COVID-19 em diferentes países. O modelo logístico é usado principalmente em epidemiologia e fornece informações sobre a dinâmica de transmissão do vírus. Os dados são da Universidade Johns Hopkins. Observamos, no entanto, que para avaliar a dinâmica de transmissão do COVID-19, são necessários modelos mais refinados, que levam em consideração as medidas específicas adotadas em cada país.



2. Magnetic field and rotation of the newborn neutron star in binary-driven hypernovae inferred from the X-ray afterglow of long gamma-ray bursts

O novo artigo, em co-autoria de Rueda, J.A., Ruffini R., Karlica M., Moradi R., Wang Y., Magnetic Fields and Afterglows of BdHNe Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C, foi publicado por The Astrophysical Journal, 893:148 em 20 de abril de 2020. Nessa ocasião, ICRA e ICRANet divulgaram um comunicado à imprensa intitulado “Magnetic field and rotation of the newborn neutron star in binary-driven hypernovae inferred from the X-ray afterglow of long gamma-ray bursts”.
Referido comunicado, disponível no site da ICRANet (http://www.icranet.org/communication/18052020/eng.pdf), foi divulgado pela American Astronomical Society AAS em 18 de maio de 2020 (em inglês) e pelo INAF (http://www.inaf.it/it/notizie-inaf/campo-magnetico-e-rotazione-della-stella-di-neutroni-neonata-nelle-ipernove-binary-driven-derivato-dall2019afterglow-x-dei-lampi-di-raggi-gamma-lunghi) em 25 de maio de 2020 (em italiano).

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Comunicado de imprensa do ICRA-ICRANet (em inglês):

The change of paradigm in gamma-ray burst (GRBs) physics and astrophysics introduced by the binary driven hypernova (BdHN) model, proposed and applied by the ICRA-ICRANet-INAF members in collaboration with the University of Ferrara and the University of Côte d'Azur, has gained further observational support from the X-ray emission in long GRBs. These novel results are presented in the new article [1], published on April 20, 2020, in The Astrophysical Journal, co-authored by J. A. Rueda, Remo Ruffini, Mile Karlica, Rahim Moradi, and Yu Wang.
The GRB emission is composed by episodes: from the hard X-ray trigger and the gamma-ray prompt emission, to the high-energy emission in GeV, recently observed also in TeV energies in GRB 190114C, to the X-ray afterglow. The traditional model of GRBs attempts to explain the entire GRB emissions from a single-component progenitor, i.e. from the emission of a relativistic jet originating from a rotating black hole (BH). Differently, the BdHN scenario proposes GRBs originate from a cataclysmic event in the last evolutionary stage of a binary system composed of a carbon-oxygen (CO) star and a neutron star (NS) companion in close orbit. The gravitational collapse of the iron core of the CO star produces a supernova (SN) explosion ejecting the outermost layers of the star, and at the same time, a newborn NS (νNS) at its center. The SN ejecta trigger a hypercritical accretion process onto the NS companion and onto the νNS. Depending on the size of the orbit, the NS may reach, in the case of short orbital periods of the order of minutes, the critical mass for gravitational collapse, hence forming a newborn BH. These systems where a BH is formed are called BdHN of type I. For longer periods, the NS gets more massive but it does not form a BH. These systems are BdHNe II. Three-dimensional simulations of all this process showing the feasibility of its occurrence, from the SN explosion to the formation of the BH, has been recently made possible by the collaboration between ICRANet and the group of Los Alamos National Laboratory (LANL) guided by Prof. C. L. Fryer, see Figure 1 and [2].
The role of the BH for the formation of the high-energy GeV emission has been recently presented in The Astrophysical Journal in [3]. There, the"engine" composed of a Kerr BH, with a magnetic field aligned with the BH rotation axis immersed in a low-density ionised plasma, gives origin, by synchrotron radiation, to the beamed emission in the MeV, GeV, and TeV, currently observed only in some BdHN I, by the Fermi-LAT and MAGIC instruments. In the new publication [1], the ICRA-ICRANet team addresses the interaction of the νNS with the SN due to hypercritical accretion and pulsar-like emission. They show that the fingerprint of the νNS appears in the X-ray afterglow of long GRBs observed by the XRT detector on board the Niels Gehrels Swift observatory. Therefore, the νNS and the BH have well distinct and different roles in the long GRB observed emission.
The emission from the magnetized νNS and the hypercritical accretion of the SN ejecta into it, gives origin to the afterglow observed in all BdHN I and II subclasses. The early (~few hours) X-ray emission during the afterglow phase is explained by the injection of ultra-relativistic electrons from the νNS into the expanding ejecta, producing synchrotron radiation; see Figure 2. The magnetic field inferred from the synchrotron analysis agrees with the expected toroidal/longitudinal magnetic field component of the νNS. Furthermore, from the analysis of the XRT data of these GRBs at times t>104 s, it has been shown that the power-law decaying luminosity is powered by the νNS rotational energy loss by the torque acted upon it by its dipole+quadrupole magnetic. From this, it has been inferred that the νNS possesses a magnetic field of strength ~ 1012-1013 G, and a rotation period of the order of a millisecond; see Figure 3. It is shown in [1], that the inferred millisecond rotation period of the νNS agrees with the conservation of angular momentum in the gravitational collapse of the iron core of the CO star which the νNS came from.
The inferred structure of the magnetic field of the "inner engine"' agrees with a scenario in which, along the rotational axis of the BH, it is rooted in the magnetosphere left by the NS that collapsed into a BH. On the equatorial plane, the field is magnified by magnetic flux conservation.

[1] J. A. Rueda, R. Ruffini, M. Karlica, R. Moradi, and Y. Wang, Astroph. J. 893, 148 (2020), 1905.11339.
[2] L. Becerra, C. L. Ellinger, C. L. Fryer, J. A. Rueda, and R. Ruffini, Astroph. J. 871, 14 (2019), 1803.04356.
[3] R. Ruffini, R. Moradi, J. A. Rueda, L. Becerra, C. L. Bianco, C. Cherubini, S. Filippi, Y. C. Chen, M. Karlica, N. Sahakyan,et al., Astroph. J. 886, 82 (2019).


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Figure 1. Taken from [1]. Schematic evolutionary path of a massive binary up to the emission of a BdHN. (a) Binary system composed of two main-sequence stars, say 15 and 12 solar masses, respectively. (b) At a given time, the more massive star undergoes the core-collapse SN and forms a NS (which might have a magnetic field B∼1013 G). (c) The system enters the X-ray binary phase. (d) The core of the remaining evolved star, rich in carbon and oxygen, for short CO star, is left exposed since the hydrogen and helium envelope have been striped by binary interactions and possibly multiple common-envelope phases (not shown in this diagram). The system is, at this stage, a CO-NS binary, which is taken as the initial configuration of the BdHN model [2]. (e) The CO star explodes as SN when the binary period is of the order of few minutes, the SN ejecta of a few solar masses start to expand and a fast rotating, newborn NS, for short νNS, is left in the center. (f) The SN ejecta accrete onto the NS companion, forming a massive NS (BdHN II) or a BH (BdHN I; this example), depending on the initial NS mass and the binary separation. Conservation of magnetic flux and possibly additional MHD processes amplify the magnetic field from the NS value to B∼1014 G around the newborn BH. At this stage the system is a νNS-BH binary surrounded by ionized matter of the expanding ejecta. (g) The accretion, the formation and the activities of the BH contribute to the GRB prompt gamma-ray emission and GeV emission.

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Figure 2. Taken from [1]. Model evolution of synchrotron spectral luminosity at various times compared with measurements in various spectral bands for GRB 160625B.

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Figure 3. Taken from [1]. The brown, deep blue, orange, green and bright blue points correspond to the bolometric (about ∼ 5 times brighter than the soft X-ray observed by Swift-XRT data) light-curves of GRB 160625B, 160509A, 130427A, 190114C and 180728A, respectively. The solid lines are theoretical light-curves obtained from the rotational energy loss of the νNS powering the late afterglow (t ≥ 5 × 103 s, white background), while in the earlier times (3 × 102 ≤ t ≤ 5 × 103 s, blue background), the kinetic energy of the SN ejecta plays also an important role. Because of the necessity of having a significant sample to extract the physical properties of the νNS (magnetic field and rotation rate), the analysis was limited to late part of the afterglow, say at times t ≥ 3 × 102 s, where data are more available. At earlier times, only GRB 130427A and GRB 190114C in this same have available data.


Link ao artigo em ApJ:
https://doi.org/10.3847/1538-4357/ab80b9

Comunicado de imprensa da ICRA-ICRANet:
http://www.icranet.org/communication/18052020/eng.pdf

Comunicado de imprensa do INAF: http://www.inaf.it/it/notizie-inaf/campo-magnetico-e-rotazione-della-stella-di-neutroni-neonata-nelle-ipernove-binary-driven-derivato-dall2019afterglow-x-dei-lampi-di-raggi-gamma-lunghi#null



3. O governo da Armênia atribui um bolsa de Doutorado à ICRANet-Armênia, 21 de maio de 2020

No dia 21 de maio de 2020, o Governo da República da Armênia aprovou as bolsas de doutorado para o ano acadêmico 2020-2021. Uma dessas bolsas foi atribuída ao centro da ICRANet-Armênia. Mais uma bolsa será atribuída no mês de junho. O exame final para admissão será realizado no final de junho.
ThA comunicação oficial está disponíveis no site do sistema de informações legais armênio (em armênio): http://www.arlis.am/DocumentView.aspx?DocID=142700



4. “Gerbertus 2020 – Scientific Rationale”, podcast meeting, 7 de maio de 2020 (em inglês)

C. Sigismondi, ICRA/Sapienza

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Figure 4: Silvestro II (1854, Turin).


The annual congress in honor of Gerbert of Aurillac, scientist, scholastic astronomer and Pope, has been inaugurated on Thursday, May 7, 2020. This event has been coordinated, as the two previous ones on November 2019 and January 2020, by and in the ICRANet center in Pescara at international level.
The program of the 2020 meeting is centered on the Moon: how it was seen 1000 years ago... the Moon of Gerbert, with the idea of reflecting on a great part of the history of astronomy and cultural heritage. Students fromHigh School Galileo Galilei in Pescara as well as students from the Technical Industrial Institute Galileo Ferraris in Rome, participating in European Programs of Didactic Empowerment (PON projects), are working on the main subjects of the program.
Among the motivations to study Gerbert I propose a selection:"Why Gerbert has not a crater on the Moon, being the first to spread a treatise on the Astrolabe before the year 1000?"
He taught Astronomy among the Quadrivium in the Cathedral of Reims in France and was considered as a scientific reference for many centuries after his death in Mathematical Computus, having also been the first man using Arabic numbers and an abacus,as well as in Music. He left to the literature a treatise in Geometry and 220 letters epistolary (Patrologia Latina volume 90): a unique case of preservation of this medieval culture. Hermann of Reichenau, half a century later, was supposed to be the author of that treatise of the astrolabe, but it has been proved that the original author was Gerbert. Hermann has his own crater and Gerbert not...moreover,Gerbert built the first documented equatorial mount described in his epistolarium (to Constantine, 980 AD on which I wrote a book, La Sfera da Gerberto al Sacrobosco, Athenaeum Regina Apostolorum, Roma 2009).
The standard of astronomical names commission avoid religious leaders, but in this case Gerbert was respected in all Europe as the most known man of his time, when he was elected Pope by Otto III in 999, according to the uses of the time, and Gerbert chose the name Sylvester II.A late medieval legend (in Wilhelm of Malmesbury and in Benno of Osnabruck), transformed him into a magician, who built a head (a Golem) able to say "yes"or"no" through which Gerbert knew that he would not die unless going to Jerusalem. On May 3, 1003, he went to celebrate Mass in the roman church of the Holy Cross, named today S. Croce in Jerusalem and at his time "Basilica Hierusalem" built by Constantine's mother Helen, bringing the ground of Jerusalem there after having found the relic of the Cross.During this Mass, Gerbert felt ill and understood that the end was approaching, so that the Golem's prediction was satisfied. He died on May 12, 1003 and that's the reason why we celebrate the congress in the first part of May, after 2003, a millennium after his death. He was buried in the Lateran's Roman Cathedral.
The slow process of Gerbert's rehabilitation happened in 1620 with a Polish Dominican Bzovsky and following the publication of his epistolarium and textbooks in the Patrologia Latina around 1700 (now in wikipedia, Latin section). In the second part of the 19° century, Nicolay Bubnov published, in Russia, his mathematical works (1899) now available as google books. In 1970, Klaus Jurgen Sachs founded a manuscript in Madrid on the musical treatise De Mensura Fistularum, of the 11° century with the attribution to Gerbert, further proving that he was the real center of the contemporary culture before and after 1000. Clyde Brockett in 1995 and Flavio G. Nuvolone (1942-2019) have deeply studiedthe encrypted composition "Carme Figuratum" (980) written by Gerbert to Otto II, including the Arabic numbers he first introduced in latin Europe.The approach to Gerbert's study is necessarily inter-multi disciplinary and the surprises are not over. Our duties are to maintain those studies and promoting their development through the web also by using the vehicle of the academic Journal Gerbertus, founded in 2010 in the Paris Observatory with three ISSN: paper, CD e online.The 2020 edition acknowledges the immense contribution to Gerbert's studies, carried on by Professor Flavio Giuseppe Nuvolone (September 2, 1942 - December 11, 2019) who published several books on Gerbert and guided numerous meetings since 1983, when he started to collaborate with Michele Tosi at Bobbio's journal ArchivumBobiense.His primary activity was in Freiburg University as chair of Pathrology, but he become amultidisciplinary investigator trying to encompass the figure of Gerbert.Talking with him was a way to enter in direct contact with the spirit and the milieu in which Gerbert acted. The resilience of Gerbert's life, and his solid Catholic faith, were shared by Professor Nuvolone with great discretion and depth.
The lossof George V. Coyne (January 19, 1933- February 11,2020), former director of SpecolaVaticana, is, for the scientific community, the loss of a person who naturally conducted a life of synergy between science and faith, similarly as Gerbert did. Both are remembered on this occasion.
The arguments belonging to bothany, philosophy, didactic, optics, Solar physics, always intend to invite young students to approach the study of sciences, as Gerbert first let possible in his Cathedral School of Reims, with the teaching of quadrivium (mathematics, geometry, astronomy and music) along with the classical trivium (grammar, rethoric, dialectic), which he interpreted as studying also profaneLatin writers and Aristotle.The musical contribution prepared by Stefano Carciofalo Parisse is an homage to the great master Gerbert, author either of the music and of a theoretical treatise on it in 980, De Mensura Fistularum.A crater on the Moon should be dedicated to Gerbert, at least, and in the Earth side face.
For more information about the event, its program and the downloadable material, please see: http://www.icranet.org/index.php?option=com_content&task=view&id=1317
The academic journal dedicated to Gerbert, the history of medieval science and to the didactic is available at the following link: http://www.icra.it/gerbertus



5. Webinar COVID, Tucson, EUA, 19 de maio de 2020


No dia 19 de maio, o Prof. Ruffini participou do webinar COVID, organizado pelo Prof. Johan Rafelski em Tucson (Arizona, EUA). O mesmo Prof. Rafelski abriu o evento e, em seguida, o Prof. Giorgio Torrieri, em colaboração com o Prof.Alessio Notari, conversou sobre os fatores de risco de transmissão COVID-19. O evento continuou com a palestra “Real danger: critical COVID-triggers seen in statistical analysis” do professor Ruffini, em colaboração com o professor Narek Sahakyan (diretor da ICRANet Armênia) e com a palestra do professor Berndt Muller sobre a análise confiável do COVID-19 e resultados. Finalmente, o professor John W. Clark apresentou suas considerações.

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Figura 5: Prof. Ruffini durante o webinar COVID, organizado pelo Prof. Johan Rafelski em Tucson, 19 de maio de 2020.


O evento, gravado, pode ser visto no:
• Site da ICRANet:
http://www.icranet.org/index.php?option=com_content&task=view&id=1321

• Site da Universidade do Arizona:
https://arizona.hosted.panopto.com/Panopto/Pages/Viewer.aspx?tid=26f8fd43-c2a2-43ac-802d-abc0015fee02
• Zoom playback:
https://arizona.zoom.us/rec/share/yuJxcqv-rD9Oc5Hv9ESFS598HJriT6a8gCYarvsNmEhEopGz7QhSImdAteDITbBw



6. O Quarto Encontro Zeldovich torna-se virtual


Em consideração da atual situação emergencial causada pela COVID-19, o Quarto Encontro Zeldovich torna-se um encontro virtual e será realizado de 7 a 11 de setembro de 2020, fruto da colaboração entre a ICRANet (organizadora) e a Academia Nacional de Ciências da Bielorrússia (anfitriã). Todos os participantes que se inscreveram até o momento são confirmados.
A participação será gratuita, o prazo de inscrição foi prorrogado até 31 de julho de 2020 e o prazo de submissão dos abstacts foi prorrogado até 15 de agosto de 2020. As atas serão publicadas na revista Astronomy Reports.
Mais detalhes disponíveis no site da conferência: http://www.icranet.org/zeldovich4



7. Convite à apresentação de propostas conjuntas “BRFFR – ICRANet 2020”


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Em abril de 2020, a BRFFR (Fundação Republicana da Bielorrússia para a Pesquisa Fundamental, pela sua sigla em inglês) e a ICRANet anunciaram um convite à apresentação de propostas para projetos conjuntos de pesquisa básica em astrofísica relativística nas seguintes áreas: astrofísica relativística, cosmologia e gravitação. As propostas conjuntas formuladas por equipes de pesquisa internacionais, incluíndo cientistas da Bielorrússia, devem ser submetidas sincronicamente, utilizando os formulários disponibilzados por ambas as organizações: as equipes bielorrussas terão que se candidatar junto à BRFFR, as equipes internacionais junto à ICRANet. O prazo máximo para concluir os projetos é de até 2 anos; o prazo de inscrição termina no dia 15 de setembro de 2020.
Para mais informações e para baixar o formulário de inscrição, acesse:
http://www.icranet.org/index.php?option=com_content&task=view&id=1311



8. Últimas publicações

Rueda, J. A., Ruffini R., Karlica M., Moradi R., Wang Y., Magnetic Fields and Afterglows of BdHNe Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C, 893:148 (13pp), 2020 April 20.
GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from initial supernova (SN) appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory, which is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs, with progenitors a binary system composed of a carbon-oxygen star (COcore) and a neutron star (NS) companion. The COcore explodes as an SN, leaving at its center a newborn NS (νNS). The SN ejecta hypercritically accretes on both the νNS and the NS companion. BdHNe I arevery tight binaries, where the accretion leads the companion NS to gravitationally collapse into a black hole (BH). In BdHN II, the accretion rate onto the NS is lower, so there is no BH formation. We observe the same afterglow structure for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all cases, the afterglows are explained via the synchrotron emission powered by the νNS, and their magnetic field structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, which was inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.
Link: https://doi.org/10.3847/1538-4357/ab80b9


Li, Liang, Thermal Components in Gamma-Ray Bursts. II. Constraining the Hybrid Jet Model, The Astrophysical Journal, Volume 894, Issue 2, id.100.
In explaining the physical origin of the jet composition of gamma-ray bursts (GRBs), a more general picture, i.e., the hybrid jet model (which introduced another magnetization parameter σ0 on the basis of the traditional fireball model), has been well studied in Gao & Zhang. However, it still has not yet been applied to a large GRB sample. Here, we first employ the "top-down" approach of Gao & Zhang to diagnose the photosphere properties at the central engine to see how the hybrid model can account for the observed data as well, through applying a Fermi GRB sample (eight bursts) with the detected photosphere component, as presented in Li (our Paper I). We infer all physical parameters of a hybrid problem with three typical values of the radius of the jet base (r0 = 107, 108, and 109 cm). We find that the dimensionless entropy for all the bursts shows η≫ 1 while the derived (1+σ0) for five bursts (GRB 081224, GRB 110721A, GRB 090719, GRB 100707, and GRB 100724) is larger than unity, indicating that in addition to a hot fireball component, another cold Poynting-flux component may also play an important role. Our analysis also shows that in a few time bins for all r0 in GRB 081224 and GRB 110721A, the magnetization parameter at ∼1015 cm (1+σr15) is greater than unity, which implies that internal-collision-induced magnetic reconnection and turbulence may be the mechanism to power the nonthermal emission, rather than internal shocks. We conclude that the majority of bursts (probably all) can be well explained by the hybrid jet problem.
Link: https://iopscience.iop.org/article/10.3847/1538-4357/ab8014


Vereshchagin, G. V.; Siutsou, I. A., Diffusive photospheres in gamma-ray bursts, Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 1, pp.1463-1469, April 2020.
Photospheric emission may originate from relativistic outflows in two qualitatively different regimes: last scattering of photons inside the outflow at the photospheric radius or radiative diffusion to the boundary of the outflow. In this work, the measurement of temperature and flux of the thermal component in the early afterglows of several gamma-ray bursts along with the total flux in the prompt phase is used to determine initial radii of the outflow as well as its Lorentz factors. Results indicate that in some cases the outflow has relatively low Lorentz factors (Γ< 10), favouring cocoon interpretation, while in other cases Lorentz factors are larger (Γ> 10), indicating diffusive photospheric origin of the thermal component, associated with an ultra relativistic outflow.
Link: https://doi.org/10.1093/mnras/staa868


Cheng-Jun Xia, She-Sheng Xue, Ren-Xin Xu, and Shan-Gui Zhou, "Supercritically charged objects and electron-positron pair creation", Phys. Rev. D, Vol. 101, Iss. 10 — 15 May 2020.
We investigate the stability and e+e- pair creation of supercritically charged superheavy nuclei, udQM nuggets, strangelets, and strangeon nuggets based on the Thomas-Fermi approximation. The model parameters are fixed by reproducing masses and charge properties of these supercritically charged objects reported in earlier publications. It is found that udQM nuggets, strangelets, and strangeon nuggets may be more stable than 56Fe at the baryon number A≳315,5×104, and 1.2×108, respectively. For those stable against neutron emission, the most massive superheavy element has a baryon number ∼965, while udQM nuggets, strangelets, and strangeon nuggets need to have baryon numbers larger than 39, 433, and 2.7×105. The e+e- pair creation will inevitably start for superheavy nuclei with charge numbers Z≥177, for udQM nuggets with Z≥163, for strangelets with Z≥192, and for strangeon nuggets with Z≥212. A universal relation Q/Re=(me--μe)/α is obtained at a given electron chemical potential -μe, where Q is the total charge and Re the radius of electron cloud. The maximum number of Q without causing e+e- pair creation is then fixed by taking -μe=-me. For supercritically charged objects with -μe<-me, the decay rate for e+e- pair production is estimated based on the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation. It is found that most positrons are emitted at t≲10-15 s, while a long lasting positron emission can be observed for large objects with R≳1000  fm. The emission of positrons and electron-positron annihilation from supercritically charged objects may be partially responsible for the short γ-ray burst during the merger of binary compact stars, the 511 keV continuum emission, as well as the narrow faint emission lines in x-ray spectra from galaxies and galaxy clusters.
Link: https://doi.org/10.1103/PhysRevD.101.103031



9. Avaliação interna do artigo do Dr Liang Li “Thermal Components in Gamma-Ray Bursts. II. Constraining the Hybrid Jet Model” publicado em ApJS

Since the early days, the standard model for Gamma-Ray Bursts (GRBs) attempted to explain all the different phases of the GRB event (precursor, prompt emission, afterglow, high-energy GeV emission, ecc.) as originating from a single ultrarelativistically expanding jet. Also within ICRANet it was initially followed a similar approach. However, after twenty years of observations, and thanks to the much better observational data provided by the new satellites, it became increasingly difficult to deal with the unveiling richness of the GRB phenomenon within this simple traditional approach. Therefore, ICRANet scientists started to follow a completely alternative approach in which all the different phases of the GRB event come from different physical processes occurring in the progenitor binary system, without involving necessarily ultrarelativistic dynamics. It is therefore important at this stage to have papers analyzing GRB observations within the two different approaches, the traditional and the alternative one, to present the corresponding possible strengths and weaknesses.
The paper by Liang Li "Thermal Components in Gamma-Ray Bursts. II. Constraining the Hybrid Jet Model" published in The Astrophysical Journal Supplement Series, 242:16, 2019, uses the traditional approach and follows the previous work on identification of thermal emission in GRBs and its interpretation as the photospheric emission in the fireball model. This work follows the idea introduced in the paper by Zhang et al. [Nature Astronomy, 2 (2018) 69], who interpreted emission in GRB 160625B as transition from unmagnetized to magnetized fireball. This work was extended by Liang Li in the paper published previously in The Astrophysical Journal Supplement Series, 242:16, 2019. The physical model behind this picture is developed by Gao and Zhang [ApJ, 801 (2015) 103]. There, in addition to the dimensionless entropy eta they introduce a magnetization parameter sigma. It was shown in the paper by Meszaros and Rees, ApJ 733:40 2011 that strongly magnetized outflows accelerate slowly, compared to unmagnetized ones. This is the main difference, causing the dependence of the observed photospheric emission on the degree of magnetization. Gao and Zhang provide analytic formula which connect the observed parameters such as luminosity, flux and temperature to the physical parameters of the underlying outflow, namely the Lorentz factor, photospheric radius, nozzle radius and magnetization parameter. The nonthermal component is not explained, it is assumed that a fraction of the jet luminosity is transformed into nonthermal radiation with a given spectrum. The top-down approach, introduced in this work based on the work of Pe'er, et al., ApJL, 664, 1, 2007, and used also by Liang Li, allows to infer physical parameters of the outflow directly from the observed quantities.

The paper mentions two major shortcomings of the analysis:
1. The underlying theoretical model is based on the key assumption that both the GRB prompt emission and the x-ray afterglow originate from an ultrarelativistic jet with a Lorentz Gamma factor 10^2--10^3. Such a jetted emission was introduced since the very early days of GRB modelling to reduce the GRB energy budget, and was justified with the purported presence of "achromatic jet breaks" in the x-ray afterglow light curves. However, after 20 years of observations, no real achromatic jet break has been observed in any x-ray afterglow light curve [see e.g. Pisani et al., ApJ, 833 (2016) 159]. Only some chromatic jet breaks have actually been observed, whose explanation is currently the subject of active research but which cannot be connected to an ultrarelativistic jet dynamics. Moreover, in Ruffini et al. [ApJ, 852 (2018) 53] it has been shown, in a model independent way, that in the early phases of the x-ray afterglow light curves there are clear signatures of the presence of a thermal emitter which expands with a Lorentz Gamma factor less than 4, and no evidence of an ultrarelativistic expansion. The key assumption of the presence of an ultrarelatvistic jet is therefore not supported by the X-ray afterglow data.
2. More than half of the analysed GRBs have no measured cosmological redshift. Therefore, for these sources it is not possible to define the precise cosmological rest frame. In Ruffini et al. [ApJ, 852 (2018) 53] it was shown that many of the common features of the GRB light curves become evident only when the data are analysed in the cosmological rest frame of each source but are hidden when data are seen in the observer frame.

In the conclusions of the paper it is recalled that the alternative theoretical approach to GRBs developed within ICRANet, the Induced Gravitational Collapse scenario [see e.g. Ruffini et al., ApJ, 832 (2016) 136, and references therein], does not present these shortcomings and may well account for the observations. Within this theoretical model long GRBs originate in binary systems composed by an FeCO core and a companion neutron star, named "Binary Driven Hypernovae" (BdHNe). At the basis of the phenomenon there is not a single ultrarelativistic jet, but each phase of the GRB emission (prompt gamma-ray emission, early X-ray afterglow emission, late x-ray afterglow emission, GeV emission, etc.) comes from a different physical process occurring in the progenitor binary system. The entire photospheric emission is currently being reconsidered within this new approach, overcoming the above shortcomings 1 and 2. In the meantime, we can already say that this new approach gives an answer about the late X-ray afterglow emission: it is due to the newly born neutron star which remains after the explosion of the FeCO core, and no ultrarelativistic dynamics is involved in this process [see e.g. Ruffini et al., ApJ, 869 (2016) 101; Rueda et al., ApJ, 893 (2020) 148].

Link to the paper: https://iopscience.iop.org/article/10.3847/1538-4357/ab8014



10. Avaliação interna do artigo em co-autoria do Prof. Shesheng Xue “Supercritically charged objects and electron-positron pair creation” publicado na revista Physical Review D


In astrophysical systems, there can possibly exist the strong coupling between nucleons and quark matters of large charge number Z and atomic number A, such as udQM nuggets, strangelets, and strangeon nuggets. In order to further understand electron-positron production in such strong coupling matter in connection with the observed phenomena, the authors of this paper study supercritically charged matter by applying the Thomas-Fermi model of chemical potential equilibrium for highly degenerate electrons and the Schwinger model of vacuum polarisation for electron-positron pair production. This research, as shown by the references below, has been well developed for years in ICRANet to understand the physical relevance of electron-positron pair production and annihilation for the astrophysical phenomena of Gamma-Ray Bursts, the 511 keV continuum emission and the narrow ~ 4 keV faint emission lines from galaxies and galaxy clusters.

9


To understand how the Coulomb energy raised in such a strong coupling matter is balanced, Authors from China use their expertise on the empirical model of Fermi type describing such a strong coupling matter. They make both analytical and numerical analyses of chemical potentials to examine the stability of strong coupling matter against pair production and to obtain the critical values of large charge number Z and atomic number A, as well as the size of strong coupling matter, see Figure. Instead, in the case of Coulomb energy being released, they make numerical calculations by using the pair-production rate in an electron degenerate system, developed within ICRANet, to approximately obtain the time scale and rate of electron-positron pair production as functions of charge number Z and atomic number A, and to give an insight into their relevance for the observations.
This work has been completed by remote collaborations via internet between: Professors Cheng-Jun Xia of Zhejiang University Ningbo Institute of Technology, Ren-Xin Xu of Peking University and Shan-Gui Zhou of Institute of Theoretical Physics, and ICRANet faculty member She-Sheng Xue. Chinese colleagues Xia, Xu and Zhou are experts on the nuclear physics and astro-nuclear physics, in particular the properties of nuclear and quark matter that composes compact stars in our Universe. They are very active in the field and have published many articles in international high impact scientific journals worldwide.

• R. Ruffini, G. Vereshchagin, and S.-S. Xue, Phys. Rep. 487, 1 (2010).
• H. Kleinert, R. Ruffini, and S.-S. Xue, Phys. Rev. D 78, 025011 (2008).
• W.-B. Han, R. Ruffini, and S.-S. Xue, Phys. Lett. B 691, 99 (2010).
• R. Ruffini and S.-S. Xue, Phys. Lett. B 696, 416 (2011).
• M. Rotondo, R. Ruffini, and S.-S. Xue, "Neutral nuclear core vs super charged one," in The Eleventh Marcel Grossmann Meeting (2008) pp. 1352-1355.
• J. Rueda, R. Ruffini, Y. Wang, Y. Aimuratov, U. B. de Almeida, C. Bianco, Y. Chen, R. Lobato, C. Maia, D. Primorac, R. Moradi, and J. Rodriguez, J. Cosmol. Astropart. P. 2018, 006 (2018).

Link to the paper: https://doi.org/10.1103/PhysRevD.101.103031
 
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