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ICRANet Newsletter



ICRANet Newsletter
December 2018 - January 2019



SUMMARY
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. In memory of Riccardo Giacconi, 6 October 1931 - 9 December 2018
3. Professor Ruffini visit to Tsinghua University (Beijing), 8 -15 December 2018
4. New collaboration Agreement between INAF and ICRANet, 18 December 2018
5. Professor Ruffini visit to Brazil, 16 - 18 January 2019
6. Professor Ruffini intervention at "Science by Night", Liceo Scientifico Galileo Galilei of Pescara, 19 January 2019
7. Prof. Ruffini meeting with ICTP Director and TWAS Executive Director, Trieste, 31 January 2019
8. Scientific visits to ICRANet
9. ICRANet publications up to 2018
10. Russian translation of the book "Relativistic kinetic theory" published in Moscow
11. Recent publications




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. In memory of Riccardo Giacconi, 6 October 1931 - 9 December 2018


Riccardo Giacconi, the scientist who allowed humanity to access the images of our Universe in all wavelengths from visible light to X-rays, passed away on Sunday, 9 December 2018. Founding member of ICRA and ICRANet, he has been the first President of ICRANet Scientific Committee.

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Figure 1: ICRANet Scientific Committee 2008. Figure 2: ICRANet Scientific Committee 2010. Figure 3: Group Picture ICRANet Scientific Committee 2010.


The close collaboration between Prof. Ruffini and Prof. Giacconi, went on throughout their lives, and led to the observation and identification of Cignus X-1, the first Black Hole in our Galaxy, conceptually introduced by Remo Ruffini, together with John Wheeler (https://physicstoday.scitation.org/doi/10.1063/1.3022513).

For this important work, Prof. Giacconi received the 2002 Nobel Prize in Physics (https://www.nobelprize.org/prizes/physics/2002/summary) and Prof. Ruffini received in 1973 the Cressy-Morrison Award from the New York Academy of Sciences (http://www.icranet.org/documents/Ruffini-CMorrison-award.jpg).

Prof. Giacconi realized UHURU (https://heasarc.gsfc.nasa.gov/docs/uhuru/uhuru.html), the first satellite that observed the Universe in X-Rays, launched from the Italian space station "San Marco" in Kenya, and followed by the great observatories EINSTEIN (https://heasarc.gsfc.nasa.gov/docs/einstein/heao2_about.html) and CHANDRA (http://chandra.harvard.edu/), always in X-Rays. This allowed also the subsequent development, during his mission as ESO Director, of the biggest optical telescope in the world, the VLT in Chile (https://www.eso.org/public/teles-instr/paranal-observatory/vlt/).

In Beijing, Professor Ruffini, commemorating Riccardo Giacconi, presented in a series of conferences, the most recent results on Gamma Ray Bursts (the GRBs), that, after almost 40 years of study and thanks to several observatories created by Riccardo in the USA and in Europe, are been revealed in all their beauty: cosmological objects that thanks to their extreme luminosity equal for a hundred of seconds to the integrated luminosity of all billions of galaxies of our Universe, each one composed of a hundred of billions of stars.
Prof. Giacconi is survived by his wife Mirella, daughters Anna and Guia, and grandchildren Alexandra and Colburn. He was pre-deceased by his son Mark.
Prof. Giacconi and John Wheeler left their dated signatures on the wall (see Fig. 5) located in the G9 room of ICRA, in the Physics Department of University of Rome "La Sapienza": the Universe becomes conscious of its existence with the presence of the Human eye (Wheeler), improved by the lenses of the X-Rays Satellites (Giacconi).


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Figure 4: Prof. Remo Ruffini, Prof. Riccardo Giacconi and the three volumes of the ICRANet Scientific report 2010. Figure 5: Riccardo Giacconi and John Wheeler dated signatures at G9.




3. Professor Ruffini visit to Tsinghua University (Beijing), 8 -15 December 2018

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Announcement of the CC Lin Lectures at Tsinghua University, Beijing.

From 8 to 15 December 2018, Professor Ruffini visited Tsinghua University in Beijing (China) together with Prof. Jorge Rueda, Prof. Shesheng Xue, Dr Yu Wang and Rahim Moradi. The ICRANet delegation was invited by Professor Shing-Tung Yau, Director of the Yau Mathematical Science Center, to deliver a series of 4 Chia-Chiao Lin distinguished lectures at Tsinghua University, one of the most important Chinese universities.

The first CC Lin Lecture "On the Relativistic Astrophysics domains" was presented by Prof. Remo Ruffini (https://youtu.be/hkEOt-kaWZI), the second CC Lin Lecture "The eight different GRB families" was presented by Prof. Rueda (https://youtu.be/2dSkvsznL5w), the third CC Lin Lecture "The long march toward the understanding of the fundamental nature of GRBs" was presented by Dr. Yu Wang (https://youtu.be/6TT9BiR9o4g) and the forth CC Lin Lecture "The GeV radiation and the "inner engine" of Gamma Ray Bursts" was presented by Prof. Xue and Rahim Moradi (https://youtu.be/-UJr6EKq3cY).
During his visit, Professor Ruffini took also part at the 11th Shing-Tung Yau High School Science Award Ceremony, founded in 2008 by Prof. Shing-Tung Yau with the desire to inspire scientific innovations among Chinese high school students all over the world.

Professor Ruffini was also invited to participate to the 2nd S.T. Yau Science Forum. Founded in 2017 by Professor Shing-Tung Yau, the forum aimed at establishing a platform for dialogue between young Chinese students and outstanding scientists and scholars with notable contributions in their respective fields, encouraging students to foster their passion for scientific research, expanding their scientific capacities and visions, and cultivating their innovative mindsets. On that occasion, Professor Ruffini delivered the lecture, titled "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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From left to right: Rahim Moradi, Dr. Wang Yu, Prof. Remo Ruffini, Prof. Shude Mao, Prof. Jorge Rueda and Prof. She-Sheng Xue. From left to right: Prof. Jorge Rueda, Prof. Remo Ruffini, Prof. Shing-Tung Yau, Prof. She-Sheng Xue and Dr Wang Yu.




4. New collaboration Agreement between INAF and ICRANet, 18 December 2018


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On the 18 of December 2018 a cooperation agreement between ICRANet and INAF was signed in the INAF headquarters in Rome. The main joint activities to be developed under the framework of this agreement will include the promotion of theoretical and observational activities within the field of Relativistic Astrophysics; the joint collaboration of faculty members, researchers, post-doctorate fellows and students; the organization of training and teaching courses, seminars, conferences, workshops or short courses, and the joint work on scientific publications.




5. Professor Ruffini visit to Brazil, 16 - 18 January 2019


From 16 to 18 January 2019, Professor Ruffini, Director of ICRANet, visited the capital of Brazil, where he had a series of meeting with Brazilian representatives, accompanied by Prof. Manuel Malheiro and Prof. Clovis Maia. On Thursday, January 17, he had a meeting at CAPES with its new President, Anderson Ribeiro Correia, in presence of the Director of International Relations: on this occasion, they had discussed the reopening of the ICRANet-Capes agreement and the President of Capes, former Rector of ITA, recognized once again the relevance of ICRANet, and the activities at ITA and the University of Brasilia. In the afternoon, Prof. Ruffini, at the Brazilian Ministery of Science, Technology, Innovation and Communication (MCTIC) met one of its main secretaries, Air Force Colonel Carlos Alberto Baptistucci. They discussed the appointment of a diplomat for the board of ICRANet, as well as a representative for the new Ministry of Finances and a member of the scientific community. Prof. Ruffini also met the Rector of the University of Brasilia, Prof. Marcia Abrahao, in presence of Prof. Clovis Maia, Prof. Vanessa Andrade, Prof. Marcos Maia, and Prof. Adalene Silva (in charge of the International Graduate Program division), and discussed about the possibility to implement ICRANet activities at her University.

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From left to right: Prof. Clovis Maia, Prof. Anderson Ribeiro Correia (President of CAPES), Prof. Remo Ruffini, Concepta Pimentel (DRI CAPES) and Prof. Manuel Malheiro.




6. Professor Ruffini intervention at "Science by Night", Liceo Scientifico Galileo Galilei of Pescara, 19 January 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".

See the interview of Professor Ruffini to TV channel Rete 8: https://www.youtube.com/watch?v=XjL2cA50LMk




7. Prof. Ruffini meeting with ICTP Director and TWAS Executive Director, Trieste, 31 January 2019


On January 31, 2019, Professor Remo Ruffini visited ICTP in Trieste and met the ICTP Director, Prof. Fernando Quevedo, and the TWAS Executive Director, Prof. Romain Murenzi. This visit was an important opportunity for them to discuss about the increase of the existing synergies for the performance of their duties and for the implementation of activities related to projects of common interest. The longstanding collaboration among ICRANet and ICTP, and ICRANet and TWAS, will continue to ensure multi-year stability to the research activity in the field of relativistic astrophysics, exploration and observation of the universe from underground, the ground and space, finding means of coordination for better implementation of national and international scientific programs.


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From left to right: Prof. Fernando Quevedo (ICTP Director), Prof. Remo Ruffini (Director of ICRANet), Prof. Romain Murenzi (TWAS Executive Director) and Prof. Sandro Scandolo (ICTP).




8. Scientific visits to ICRANet


Li Liang From the 10 December 2018, Dr Li Liang, a Chinese researcher, is visiting ICRANet center in Pescara. During his visit, he is discussing his scientific researches and having fruitful exchange of ideas with other ICRANet researchers from different parts of the world. He is also working with them on the preparation of scientific papers.




9. ICRANet publications up to 2018



We are please to inform that according to the SAO/NASA Astrophysics Data System (which is a digital library portal for researchers in astronomy and physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant) the number of publications with affiliation to ICRANet has reached in 2018 the number of 559. With the total number of citation of 8845 it results in a very high impact measured by the H-index of 45. Among the top cited papers there is a review paper "Electron-positron pairs in physics and astrophysics: From heavy nuclei to black holes" published in Physics Reports in 2010 with 253 citations. This information is now available at ICRANet website: http://www.icranet.org/index.php?option=com_content&task=view&id=304&Itemid=780. Publications of ICRANet Faculty members are available here: http://www.icranet.org/index.php?option=com_content&task=view&id=332&Itemid=806 both within NASA ADS and ArXiv databases.




10. Russian translation of the book "Relativistic kinetic theory" published in Moscow


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In December 2018 Russian translation of the monograph "Relativistic Kinetic Theory With Applications in Astrophysics and Cosmology" written by ICRANet faculty member prof. Gregory Vereshchagin in co-authorship with Alexey Aksenov from Institute of Computer Aided Design of the Russian Aacademy of Sciences, published by Cambridge University Press in 2017, has been published. The publication of this Russian edition is supported by the grant of the Russian Foundation for Basic Research, project ID: 18-12-00027. The book is published with the leading Russian publishing house "Nauka" in Moscow.
It is available at:
https://naukabooks.ru/knigi/katalog/relyativistskaya_kineticheskaya_teoriya_s_prilozheniyami_v_astrofizike_i_kosmologii-_2018/




11. Recent publications


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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