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ICRANet Boletim informativo
Decembro de 2018 - Janeiro de 2019



SUMÁRIO
1. On the ultra-relativistic Prompt Emission (UPE), the Hard and Soft X-ray Flares, and the extended thermal emission (ETE) in GRB 151027A
2. Nota de pesar pelo falecimento de Riccardo Giacconi, 6 de outubro de 1931 – 9 de dezembro de 2018
3. Visita do Professor Ruffini à Universidade Tsinghua (Pequim), 8 - 15 de Dezembro de 2018
4. Acordo de colaboração entre o INAF e a ICRANet, 18 de Dezembro de 20188
5. Visita do Professor Ruffini ao Brasil, 16 – 18 de janeiro de 2019
6. Colóquio do Professor Ruffini em ocasião do evento "Ciência à noite", da escola secundária científica Galileo Galilei em Pescara, 19 de janeiro de 2019
7. Reunião do Prof. Ruffini com o Diretor do ICTP e o Diretor Executivo da TWAS, Trieste, 31 de Janeiro de 2019
8. Visitas científicas à ICRANet
9. Publicações da ICRANet até 2018
10. Versão russa do livro “Relativistic kinetic theory”, publicado em Moscou
11. Publicações recentes




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

The paper with this title co-authored by R. Ruffini, L. Becerra, C.L. Bianco et al., has been published by the Astrophysical Journal on 20 of December 2018.

A new study by ICRANet group led by prof. Ruffini published in prestigious Astrophysical Journal on 20 of December 2018 sheds light on the time sequence of emission from binary-driven hypernova (BdHN), with progenitor a carbon-oxygen core on the verge of a supernova (SN) explosion and a binary companion neutron star (NS). The GRB 151027A is selected as a prototype and its emission is characterized by the following episodes: the Ultra-relativistic Prompt emission (UPE) and the Flare-Plateau-Afterglow phase (FPA). The model is applied to study a multiple component in the UPE phase observed in the range of 10-1000 keV as well as the Hard X-ray Flares observed in the range of 0.3-150 keV, the extended-thermal-emission (ETE), and finally the soft X-ray flare observed in the range of 0.3-10 keV.

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Fig. 1. Snapshots of the density distribution of the SN ejecta in the equatorial plane of the progenitor binary system at selected instants of time.


Fig. 1 shows three snapshots of the density distribution of the SN ejecta in the equatorial plane of the progenitor binary system composed initially of a FeCO core and a neutron star. After the SN explosion the ejecta reaches the NS companion and accretion onto NS starts. Panel (a) shows the snapshot at the time t=0 when the NS companion reaches the critical mass and leads to the formation of a BH (black dot). At point C, the NS companion collapses into a BH, and an e+e- plasma - the dyadosphere-is formed (Ruffini 1999). The remaining part of the plasma impacts with the high-density portion of the SN ejecta (point E), propagates inside the ejecta encountering a baryon load of B ∼ 101-102, and finally reaches transparency, leading to the hard X-ray flare emission (point F) in gamma-rays with an effective Lorentz factor of Γ=10 and to soft X-ray flare emission (point G) with an effective Γ=4, which are then followed by the late afterglow phases.
The main conclusion of the paper is that the UPE, the hard X-ray flare and the soft X-ray flare do not form a causally connected sequence: within the BdHN 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 ∼300 s rotation period of the HN ejecta.

The paper is available here: https://doi.org/10.3847/1538-4357/aaee68



2. Nota de pesar pelo falecimento de Riccardo Giacconi, 6 de outubro de 1931 – 9 de dezembro de 2019


Riccardo Giacconi, o cientista que permitiu que a humanidade acessasse as imagens do nosso Universo em todos os comprimentos de onda, da luz visível aos raios X, faleceu no domingo, 9 de dezembro de 2018. Membro fundador do ICRA e ICRANet, ele foi o primeiro Presidente do Comitê Científico da ICRANet.

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Figure 1: Comitê Científico da ICRANet em 2008. Figure 2: Comitê Científico da ICRANet em 2010. Figure 3: foto de grupo do Comitê Científico da ICRANet em 2010.


A estreita colaboração entre o Prof. Ruffini e o Prof. Giacconi continuou ao longo de suas vidas, e levou à observação e identificação do Cignus X-1, o primeiro Buraco Negro em nossa Galáxia, conceitualmente introduzido por Remo Ruffini e John Wheeler (https://physicstoday.scitation.org/doi/10.1063/1.3022513).

Para este importante trabalho, o Prof. Giacconi recebeu o Prêmio Nobel de Física em 2002 (https://www.nobelprize.org/prizes/physics/2002/summary) e o Prof. Ruffini recebeu em 1973 o Prêmio Cressy-Morrison da Academia de Ciências de Nova York (http://www.icranet.org/documents/Ruffini-CMorrison-award.jpg).

O Prof. Giacconi realizou o UHURU (https://heasarc.gsfc.nasa.gov/docs/uhuru/uhuru.html), o primeiro satélite que observou o Universo em raios-X, lançado da estação espacial italiana "San Marco" no Quênia, seguido pelos grandes observatórios Einstein (https://heasarc.gsfc.nasa.gov/docs/einstein/heao2_about.html) e CHANDRA (http://chandra.harvard.edu/). Isso permitiu também o desenvolvimento, durante sua missão como Diretor do ESO, do maior telescópio óptico do mundo, o VLT, no Chile (https://www.eso.org/public/teles-instr/paranal-observatory/vlt/).

Em ocasião da sua visita a Pequim, o professor Ruffini, em comemoração a Riccardo Giacconi, apresentou, em uma série de conferências, os mais recentes resultados sobre Gamma Ray Bursts que, após quase 40 anos de estudo e graças a vários observatórios realizados por Riccardo nos EUA e na Europa, revelaram-se em toda a sua beleza: objetos cosmológicos que graças à sua extrema luminosidade igual a cem segundos à luminosidade integrada de todos os bilhões de galáxias do nosso Universo, cada um composto de cem bilhões de estrelas.
O prof. Giacconi deixa a esposa Mirella, as filhas Anna e Guia e os netos Alexandra e Colburn. Seu filho Mark faleceu antes dele.
O Prof. Giacconi e John Wheeler deixaram suas assinaturas datadas na parede da sala G9 do ICRA, no Departamento de Física da Universidade “Sapienza” de Roma: o Universo torna-se consciente da sua existência com a presença do Olho Humano (Wheeler), aperfeiçoado pelas lentes dos satélites X-Rays (Giacconi).


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Figure 4: o Prof. Remo Ruffini e o Prof. Riccardo Giacconi - Comitê Científico da ICRANet em 2010. Figure 5: assinaturas do Prof. Remo Ruffini e do Prof. Riccardo Giacconi na parede da sala G9 do ICRA na Universidade Sapienza




3. Visita do Professor Ruffini à Universidade Tsinghua (Pequim), 8 - 15 de Dezembro de 2018

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Anúncio das CC Lin Lectures na Universidade de Tsinghua, Pequim.

De 8 a 15 de dezembro de 2018, o professor Ruffini visitou a Universidade de Tsinghua, em Pequim (China), juntamente com o Prof. Jorge Rueda, o Prof. Shesheng Xue, o Dr. Yu Wang e Rahim Moradi. A delegação da ICRANet foi convidada pelo Professor Shing-Tung Yau, Diretor do Centro de Ciências Matemáticas de Yau, para ministrar uma série de 4 palestras de Chia-Chiao Lin na Tsinghua University, uma das mais importantes universidades chinesas.

A primeiro CC Lin Lecture "On the Relativistic Astrophysics domains" foi apresentada pelo Prof. Remo Ruffini (https://youtu.be/hkEOt-kaWZI), a segunda CC Lin Lecture "The eight different GRB families" foi apresentada pelo Prof. Rueda (https://youtu.be/2dSkvsznL5w), a terceira "The long march toward the understanding of the fundamental nature of GRBs" foi apresentada pelo Dr. Yu Wang (https://youtu.be/6TT9BiR9o4g) e a quarta "The GeV radiation and the "inner engine" of Gamma Ray Bursts" foi apresentada pelo Prof. Xue e Rahim Moradi (https://youtu.be/-UJr6EKq3cY).
Durante essa visita, o Professor Ruffini participou também da 11a Cerimônia de Premiação Científica da Escola Secundária Shing-Tung Yau, fundada em 2008 pelo Prof. Shing-Tung Yau, visando inspirar inovações científicas entre estudantes do ensino médio chinês em todo o mundo.

O professor Ruffini foi convidado a participar do 2°. Yau Science Forum. Fundado em 2017 pelo professor Shing-Tung Yau, o fórum teve como objetivo estabelecer uma plataforma de diálogo entre jovens estudantes chineses e destacados cientistas e acadêmicos com notáveis contribuições em seus respectivos campos, visando incentivar os estudantes a fomentar sua paixão pela pesquisa científica, ampliar suas capacidades científicas bem como incentivar suas mentalidades inovadoras. Naquela ocasião, o Professor Ruffini ministrou a palestra intitulada "From the earliest visions of the Cosmos to the detection of Black Holes in our Universe" (video: https://youtu.be/vpICywnsGds).


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Da esquerda para a direita: Rahim Moradi, Dr. Wang Yu, Prof. Remo Ruffini, Prof. Shude Mao, Prof. Jorge Rueda e Prof. She-Sheng Xue. Da esquerda para a direita: Prof. Jorge Rueda, Prof. Remo Ruffini, Prof. Shing-Tung Yau, Prof. She-Sheng Xue e Dr Wang Yu.




4. Acordo de colaboração entre o INAF e a ICRANet, 18 de Dezembro de 2018


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No dia 18 de dezembro de 2018, a ICRANet celebrou um acordo de cooperação com o Instituto Nacional de Astrofísica INAF em Roma. Entre as principais atividades conjuntas a serem desenvolvidas no âmbito deste acordo estão a promoção de atividades teóricas e observacionais no campo da Astrofísica Relativista; a colaboração conjunta de docentes, pesquisadores, pós-doutorandos e estudantes; a organização de cursos de formação e ensino, seminários, conferências, workshops ou cursos de curta duração e o trabalho conjunto sobre publicações científicas.




5. Visita do Professor Ruffini ao Brasil, 16 – 18 de janeiro de 2019


De 16 a 18 de janeiro de 2019, o Professor Ruffini visitou a capital do Brasil, onde teve uma série de encontros com representantes brasileiros, acompanhado pelos professores Manuel Malheiro e Clovis Maia. Na quinta-feira, 17 de janeiro, ele teve uma reunião na CAPES com seu novo presidente, Anderson Ribeiro Correia, ex-reitor do ITA, na presença da Diretora de Relações Internacionais, na qual o tema da reinstauração do acordo ICRANet-Capes foi abordado; o mesmo presidente da CAPES reconheceu mais uma vez a relevância da ICRANet relacionada às atividades do ITA bem como da Universidade de Brasília. À tarde, o Prof. Ruffini encontrou um dos principais secretários do Ministério da Ciência, Tecnologia, Inovação e Comunicação (MCTIC) do Brasil, o coronel da Força Aérea Carlos Alberto Baptistucci. Durante essa reunião a questão da nomeação de um diplomata junto ao Conselho de Administração da ICRANet, bem como de um representante do Ministério das Finanças e de um membro da comunidade científica para o Conselho Científico foi abordada. O Prof. Ruffini teve uma reunião com a Profa. Marcia Abrahao, Reitora da Universidade de Brasília UnB e os profesores Clovis Maia, Vanessa Andrade, Marcos Maia e Adalene Silva (responsável pela divisão do Programa Internacional de Pós-Graduação) durante a qual tiveram a oportunidade de conversar sobre a possibilidade de implementar as atividades da ICRANet na UnB.

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Da esquerda para direita: Prof. Clovis Maia, Prof. Anderson Ribeiro Correia (Presidente da CAPES), Prof. Remo Ruffini, Concepta Pimentel (DRI CAPES) e Prof. Manuel Malheiro.




6. Colóquio do Professor Ruffini em ocasião do evento "Ciência à noite", da escola secundária científica Galileo Galilei em Pescara, 19 de janeiro de 2019


On January 19, 2019, the Liceo Scientifico Galileo Galilei of Pescara, organized an important event titled “Science by Night”. This event represented a nice occasion for discussion among students, citizens and researchers, and attracted a lot of people, offering visitors a unique opportunity to take part in science activities aiming to showcase both the fascination of research as a career and its significant societal impact. On that occasion, an ICRANet delegation composed by Prof. Remo Ruffini, Prof. Gregory Vereshchagin and Prof. She-Sheng Xue was invited to participate, and Prof. Ruffini deliver an important talk, titled “La fisica di Einstein applicata all'Universo. Aspetti concettuali, aspetti morali e sviluppi tecnologici”.

Veja-se a entrevista do professor Ruffini para o canal de TV Rete 8: https://www.youtube.com/watch?v=XjL2cA50LMk




7. Reunião do Prof. Ruffini com o Diretor do ICTP e o Diretor Executivo da TWAS, Trieste, 31 de Janeiro de 2019


Em 31 de janeiro de 2019, o professor Ruffini esteve em visita ao ICTP em Trieste onde encontrou o Prof. Fernando Quevedo, Diretor do ICTP, e o Prof. Romain Murenzi, Diretor Executivo da TWAS. Durante esta visita eles tiveram a oportunidade de analizar o desenvolvimento das sinergias existentes para o cumprimento dos óficios conjuntos e para a implementação de atividades relacionadas a projetos de interesse comum. A prolongada colaboração entre a ICRANet e o ICTP, e entre a ICRANet e a TWAS, continuará a assegurar a estabilidade plurianual da atividade de pesquisa no campo da astrofísica relativista, exploração e observação do universo a partir do subsolo, do solo e do espaço, encontrando meios de coordenação para melhor implementação de programas científicos nacionais e internacionais.


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Da esquerda para direita: Prof. Fernando Quevedo (Diretor do ICTP), Prof. Remo Ruffini (Diretor da ICRANet), Prof. Romain Murenzi (Diretor Executivo da TWAS) e Prof. Sandro Scandolo (ICTP).




8. Visitas científicas à ICRANet


Li Liang Desde o dia 10 de dezembro de 2018, o Dr. Li Liang, pesquisador chinês, está em visita ao centro ICRANet em Pescara para continuar o trabalho de pesquisa científica e ter frutuosas trocas de idéias com outros pesquisadores da ICRANet, com quem está colaborando na preparação de artigos científicos.




9. Publicações da ICRANet até 2018



emos o prazer de informar que, de acordo com o SAO/NASA Astrophysics Data System (portal de biblioteca digital para pesquisadores em astronomia e física, realizado pelo Smithsonian Astrophysical Observatory-SAO financiado pela NASA), em 2018 as publicações com afiliação ICRANet atingiram o número de 559. Com um número total de 8845 citações, a ICRANet tem alto impacto (índice-H de 45). Entre os artigos mais citados está "Electron-positron pairs in physics and astrophysics: From heavy nuclei to black holes", publicado em Physics Reports em 2010, com 253 citações. Para mais informações acesse: http://www.icranet.org/index.php?option=com_content&task=view&id=304&Itemid=780. Para as publicações da ICRANet (ADS e ArXiv da NASA) acesse: http://www.icranet.org/index.php?option=com_content&task=view&id=332&Itemid=806.




10. Versão russa do livro "Relativistic kinetic theory", publicado em Moscou


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Em dezembro de 2018, foi publicada a tradução russa da monografia "Teoria Cinética Relativística com Aplicações em Astrofísica e Cosmologia" escrita pelo prof. Gregory Vereshchagin em co-autoria com Alexey Aksenov do Instituto Computer Aided Design da Academia Russa de Ciências, publicado pela Cambridge University Press em 2017. A publicação da edição em russo foi financiada pela Fundação Russa de Pesquisa Básica, projeto ID: 18-12-00027. O livro é publicado com a principal editora russa "Nauka" em Moscou.
Para o livro acesse:
https://naukabooks.ru/knigi/katalog/relyativistskaya_kineticheskaya_teoriya_s_prilozheniyami_v_astrofizike_i_kosmologii-_2018/




11. Publicações recentes


Becerra, L.; Ellinger, C. L.; Fryer, C. L.; Rueda, J. A.; Ruffini, R., SPH simulations of the induced gravitational collapse scenario of long gamma-ray bursts associated with supernovae, The Astrophysical Journal, Volume 871, Issue 1, article id. 14, published on 18 January 2019.

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Fig. 2. Surface density on the equatorial binary plane of the SN expansion under the presence of its NS companion at different times. These plots correspond to the SPH simulation of the IGC scenario for an initial binary system composed by a NS of 2 Msun and the COcore of a Mzams=25 Msun progenitor with an initial orbital period of about 5 mins. The NS companion is at the origin and the nu-NS is along the -x-axis.


We present the first three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) simulations of the induced gravitational collapse (IGC) scenario of long-duration gamma-ray bursts (GRBs) associated with supernovae (SNe). We simulate the SN explosion of a carbon-oxygen core (COcore) forming a binary system with a neutron star (NS) companion. We follow the evolution of the SN ejecta, including their morphological structure, subjected to the gravitational field of both the new NS (νNS) formed at the center of the SN, and the one of the NS companion. We compute the accretion rate of the SN ejecta onto the NS companion as well as onto the νNS from SN matter fallback. We determine the fate of the binary system for a wide parameter space including different COcore and NS companion masses, orbital periods and SN explosion geometry and energies. We identify, for selected NS nuclear equations-of-state, the binary parameters leading the NS companion, by hypercritical accretion, either to the mass-shedding limit, or to the secular axisymmetric instability for gravitational collapse to a black hole (BH), or to a more massive, fast rotating, stable NS. We also assess whether the binary remains or not gravitationally bound after the SN explosion, hence exploring the space of binary and SN explosion parameters leading to νNS-NS and νNS-BH binaries. The consequences of our results for the modeling of long GRBs, i.e. X-ray flashes and binary-driven hypernovae, are discussed.

Link: https://doi.org/10.3847/1538-4357/aaf6b3


M. A. Prakapenia, I. A. Siutsou, G. V. Vereshchagin, Thermalization of electron-positron plasma with quantum degeneracy, Physics Letters A Volume 383, Issue 4, p. 306, published on 17 January 2019.

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Fig. 3. Energy density spectra at selected time moments for photon (Boltzmann: blue; Planck: cyan; Bose-Einstein: green) and pairs (Boltzmann: orange; Fermi-Dirac: red).


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


Punsly, Brian; Tramacere, Andrea; Kharb, Preeti; Marziani, Paola, The Powerful Jet and Gamma-Ray Flare of the Quasar PKS 0438-436, The Astrophysical Journal, Volume 869, Issue 2, article id. 174, published on 26 December 2018.

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Fig. 4. Comparison of the two spectra.


PKS 0438-436 at a redshift of z=2.856 has been previously recognized as possessing perhaps the most luminous known synchrotron jet. Little is known about this source since the maximum elevation above the horizon is low for the Very Large Array (VLA). We present the first VLA radio image that detects the radio lobes. We use both the 151 MHz luminosity, as a surrogate for the isotropic radio lobe luminosity, and the lobe flux density from the radio image to estimate a long term, time averaged, jet power 1.5±0.7×1047ergs s-1. We analyze two deep optical spectra with strong broad emission lines and estimate the thermal bolometric luminosity of the accretion flow, Lbol=6.7±3.0×1046ergs s-1. The ratio 3.3±2.6, is at the limit of this empirical metric of jet dominance seen in radio loud quasars and this is the most luminous accretion flow to have this limiting behavior. Despite being a very luminous blazar, it previously had no γ-ray detections (EGRET, AGILE or FERMI) until December 11 - 13 2016 (54 hours) when FERMI detected a flare that we analyze here. The isotropic apparent luminosity from 100 MeV - 100 GeV rivals the most luminous detected blazar flares (averaged over 18 hours), ∼5-6×1049 ergs s-1. The γ-ray luminosity varies over time by two orders of magnitude, highlighting the extreme role of Doppler abberation and geometric alignment in producing the inverse Compton emission.

Link: https://doi.org/10.3847/1538-4357/aaefe7


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, The Astrophysical Journal Volume 869, Issue 2, article id. 151, published on 20 December 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://doi.org/10.3847/1538-4357/aaee68


Punsly, Brian; Marziani, Paola; Bennert, Vardha N.; Nagai, Hiroshi; Gurwell, Mark A., Revealing the Broad Line Region of NGC 1275: The Relationship to Jet Power 2018, The Astrophysical Journal, Volume 869, Issue 2, article id. 143, published on 19 December 2018.

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Fig. 5. The widest plausible NL fit to CIV in 2011.352 still results in a significant redwing residual.


NGC 1275 is one of the most conspicuous active galactic nuclei (AGN) in the local Universe. The radio jet currently emits a flux density of 10 Jy at 1 mm wavelengths, down from the historic high of 65 Jy in 1980. Yet, the nature of the AGN in NGC 1275 is still controversial. It has been debated whether this is a broad emission line (BEL) Seyfert galaxy, an obscured Seyfert galaxy, a narrow line radio galaxy or a BL-Lac object. We clearly demonstrate a persistent Hβ BEL over the last 35 years with a full width half maximum (FWHM) of 4150 - 6000 km/s. We also find a prominent Pα BEL (FWHM = 4770 km/s) and a weak CIV BEL (FWHM = 4000 km/s), Hβ/CIV = 2. A far UV HST observation during suppressed jet activity reveals a low luminosity continuum. The Hβ BEL luminosity is typical of broad line Seyfert galaxies with similar far UV luminosity. X-ray observations indicate a softer ionizing continuum than expected for a broad line Seyfert galaxy with similar far UV luminosity. This is opposite of the expectation of advection dominated accretion. The AGN continuum appears to be thermal emission from a low luminosity, optically thick, accretion flow with a low Eddington ratio, = 0.0001. The soft, weak ionizing continuum is consistent with the relatively weak CIV BEL. Evidence that the BEL luminosity is correlated with the jet mm wave luminosity is presented. Apparently, the accretion rate regulates jet power.

Link: https://doi.org/10.3847/1538-4357/aaec75


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, The Astrophysical Journal, Volume 869, Issue 2, article id. 101, published on 14 December 2018.

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Fig. 6. The observed luminosity of GRB 130427A in the 0.3-50 keV band (gray points), and the theoretical luminosity from a pulsar for selected quadrupole to dipole magnetic field ratio and quadrupole angles in color lines.


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 ∼1014G. 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://doi.org/10.3847/1538-4357/aaeac8


Damien Bégué, Clément Stahl, She-ShengXue, A model of interacting dark fluids tested with supernovae and Baryon Acoustic Oscillations data, published in Nuclear Physics B 940, 312 on 8 January 2019.

We compare supernovae and Baryon Acoustic Oscillations data to the predictions of a cosmological model of interacting dark matter and dark energy. This theoretical model can be derived from the effective field theory of Einstein-Cartan gravity with two scaling exponents δG and δΛ, related to the interaction between dark matter and dark energy. We perform a χ2 fit to the data to compare and contrast it with the standard Λ CDM model.
We then explore the range of parameter of the model which gives a better χ2 than the standard cosmological model. All those results lead to tight constraints on the scaling exponents of the model. Our conclusion is that this class of models, provides a decent alternative to the CDM model.

Link: https://www.sciencedirect.com/science/article/pii/S0550321319300033


Sahakyan, N., The Origin of the Multiwavelength Emission of PKS 0502+049, published in Astronomy and Astrophysics, 622, A144 on 12 February 2019.

The origin of the multiwavelength emission from PKS 0502+049 neighboring the first cosmic neutrino source TXS 0506+056 is studied using the data observed by Fermi-LAT and Swift UVOT/XRT. This source was in a flaring state in the considered bands before and after the neutrino observations in 2014-2015, characterized by hard emission spectra in the X-ray and gamma-ray bands, 1.5-1.8 and < 2.0, respectively. During the neutrino observations, the gamma-ray spectrum shows a deviation from a simple power-law shape, indicating a spectral cutoff at Ec =8.50 GeV. The spectral energy distributions of PKS 0502+049 are modeled within a one-zone leptonic scenario assuming that high energy gamma-ray emission is produced either by IC scattering of synchrotron or dusty torus photons by the electron population that produce the radio-to-optical emission. Alternatively, the observed gamma-rays are modeled considering inelastic interaction of protons, when the jet interacts with a dense gaseous target. During the neutrino observations, the gamma-ray data are best described when the proton energy distribution is Ep-2.61 and if the protons are effectively accelerated up to 10 PeV, the expected neutrino rate is 1.1 events within 110 days. In principle, if the gamma-ray emission with a hard photon index observed during the flaring periods extends up to TeV, the expected rate can be somewhat higher, but such conditions are hardly possible. Within the hadronic interpretation, the gamma-ray data can be reproduced only when the accretion rate of PKS 0502+049 is in the supper-Eddington regime, as opposed to the leptonic scenario. From the point of view of the necessary energetics as well as considering that the required parameters are physically reasonable, when the neutrinos were observed, the broadband emission from PKS 0502+049 is most likely of a leptonic origin.

Link: https://www.aanda.org/articles/aa/abs/2019/02/aa34606-18/aa34606-18.html


Suzana Bedić, Gregory Vereshchagin, Probability of inflation in Loop Quantum Cosmology, published in Physical Review D 99, 043512 on 11 February 2019.

We discuss how initial conditions for cosmological evolution can be defined in Loop Quantum Cosmology with massive scalar field and how the presence of the bounce influences the probability of inflation in this theory, compared with General Relativity. The main finding of the paper is existence of an attractor in the contracting phase of the universe, which results in special conditions at the bounce, quite independent on the measure of initial conditions in the remote past, and hence very specific duration of inflationary stage with the number of e-foldings about 140.

Link: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.99.043512


 
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