ICRANet Newsletter

Bulletin ICRANet
Décembre 2018 - Janvier 2019

English - French - Italian - Portuguese

RÉSUMÉ
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. En mémoire de Riccardo Giacconi, 6 Octobre 1931 - 9 Décembre 2018
3. Visite du Professeur Ruffini à l’Université Tsinghua (Pékin), 8 - 15 Décembre 2018
4. Nouveau Accord de Collaboration entre l’INAF et ICRANet, 18 Décembre 2018
5. Visite du Professeur Ruffini au Brésil, 16 - 18 Janvier 2019
6. Intervention du Professeur Ruffini à “Science by Night”, Lycée Scientifique Galileo Galilei de Pescara, 19 Janvier 2019
7. Meeting du Professeur Ruffini avec le Directeur de l’ICTP et le Directeur exécutif du TWAS, Trieste, 31 Janvier 2019
8. Visites scientifiques auprès du centre ICRANet de Pescara
9. Publications ICRANet jusqu’au 2018
10. Traduction en russe du livre “Relativistic kinetic theory”, publié à Moscou
11. Publications récentes

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.

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. En mémoire de Riccardo Giacconi, 6 Octobre 1931 - 9 Décembre 2018

Riccardo Giacconi, le scientifique qui a permis à l’humanité entire d’avoir acces aux images de l’Universethe scientist who allowed humanity to access the images of our Universe dans toutes les longueur d'ondes dès la lumière visible aux rayons X, est mort le Dimanche 9 Décembre 2018. Founding member of ICRA and ICRANet, he has been the first President of ICRANet Scientific Committee.

Figure 1: Le Comité Scientifique ICRANet en 2008.	Figure 2: Le Comité Scientifique ICRANet en 2010.	Figure 3: Photo de group du Comité Scientifique ICRANet en 2010.

L’étroite collaboration entre le Prof. Ruffini et le Prof. Giacconi a été menée au long de leur vie et a permis l’observation et l’identification du Cignus X-1, le premier Trou Noir dans notre galaxie, introduit conceptuellement par Remo Ruffini et John Wheeler (https://physicstoday.scitation.org/doi/10.1063/1.3022513).

Pour cet important travail, le Prof. Giacconi a reçu en 2002 le Prix Nobel en Physique (https://www.nobelprize.org/prizes/physics/2002/summary) et le Prof. Ruffini a reçu en 1973 le Cressy-Morrison Award de la New York Academy of Sciences (http://www.icranet.org/documents/Ruffini-CMorrison-award.jpg).

Le Prof. Giacconi a aussi réalisé UHURU (https://heasarc.gsfc.nasa.gov/docs/uhuru/uhuru.html), le premier satellite qui a observé l’univers en Rayons-X, lancé par la station spatiale italienne “San Marco” en Kenya, suivi par les observatoires EINSTEIN (https://heasarc.gsfc.nasa.gov/docs/einstein/heao2_about.html) et CHANDRA (http://chandra.harvard.edu/), toujours en Rayons-X. Ca a permis aussi l’ultérieur développement, pendant son mandat en qualité de Directeur de l’ESO, du plus grand télescope optique dans le monde, le VLT en Chili (https://www.eso.org/public/teles-instr/paranal-observatory/vlt/).

A Pékin, le Professeur Ruffini, a commémoré Riccardo Giacconi, en présentant dans une série de conférences, les résultats les plus récents sur les Sursaut Gamma (SRGs), qui, après environ 40 années d’études et grâce aux observatoires crées par Giacconi aux Etats-Unis et en Europe, ont été montrées dans toute leur beauté.
Le Prof. Giacconi laisse sa femme Mirella, ses filles Anna et Guia, et ses petits-fils Alexandra et Colburn. Il a été précédé par son fils Mark.
Le Prof. Giacconi et John Wheeler ont laissé leur signatures datés sur les murs (Fig. 5) de la salle G9 de l’ICRA, dans le Département de Physique de l’Université de Rome “La Sapienza”: l’univers prend conscience de sa même existence grâce aux yeux humains (Wheeler), perfectionné par les lents des Satellites X-Rays (Giacconi).

3. Visite du Professeur Ruffini à l’Université Tsinghua (Pékin), 8 - 15 Décembre 2018

Du 8 au 15 Décembre 2018, le Professeur Ruffini a visité l’Université Tsinghua à Pékin (Chine) avec le Prof. Jorge Rueda, le Prof. Shesheng Xue, le Dr Yu Wang et Rahim Moradi. La délégation ICRANet a été invite par le Professeur Shing-Tung Yau, Directeur du Yau Mathematical Science Center, à donner une série de 4 Chia-Chiao Lin distinguished lectures à l’Université Tsinghua, une des universités les plus importantes en Chine.

La première CC Lin Lecture “On the Relativistic Astrophysics domains” a été présenté par le Prof. Remo Ruffini (https://youtu.be/hkEOt-kaWZI), la seconde CC Lin Lecture “The eight different GRB families” a été présenté par le Prof. Rueda (https://youtu.be/2dSkvsznL5w), la troisième CC Lin Lecture “The long march toward the understanding of the fundamental nature of GRBs” a été présenté par Dr. Yu Wang (https://youtu.be/6TT9BiR9o4g)et la quatrième CC Lin Lecture “The GeV radiation and the “inner engine” of Gamma Ray Bursts” a été présenté par le Prof. Xue et Rahim Moradi (https://youtu.be/-UJr6EKq3cY).
Pendant sa visite, le Professeur Ruffini a aussi pris partie à la 11^th Shing-Tung Yau High School Science Award Ceremony, crée en 2008 par le Prof. Shing-Tung Yau avec le but d’inspirer des innovations scientifiques parmi les étudiants de lycée chinois du monde entier.

Le Professeur Ruffini a été aussi invitée à participer au «2^nd S.T. Yau Science Forum». Crée en 2017 par le Professeur Shing-Tung Yau, ce forum a le but d’établir une plate-forme pour le dialogue entre les jeunes étudiants chinois et les scientifiques les plus importants, pour encourager les étudiants à cultiver leur passion pour la recherche scientifique, à développer leur visions et capacités scientifiques et à cultiver leur esprit novateur.
Dans cette occasion, le Professeur Ruffini a donné un important séminaire, intitulé “From the earliest visions of the Cosmos to the detection of Black Holes in our Universe” (vidéo: https://youtu.be/vpICywnsGds).

4. Nouveau Accord de Collaboration entre l’INAF et ICRANet, 18 Décembre 2018

Le 18 Décembre 2018 un accord de collaboration entre ICRANet et INAF a été signé dans a siège principal de l’INAF à Rome. Les principales activités conjointes qui seront développées dans le cadre de cet accord comptent: la promotion des activités de recherche et d'observation dans le champ de l’astrophysique relativiste; la collaboration entre des membres de la Faculté, des chercheurs, des post-doctorat fellows et des étudiants; l’organisation de séminaires, conférences, workshops, cours de formations et de recherche, et publications conjointes.

5. Visite du Professeur Ruffini au Brésil, 16 - 18 Janvier 2019

Du 16 au 18 Janvier 2019, le Professeur Ruffini, Directeur d’ICRANet, a visité Brasilia, ou il a eu une série de meetings avec des représentants Brésiliens, accompagné par le Prof. Manuel Malheiro et le Prof. Clovis Maia. le 17 janvier, il a eu un meeting au CAPES avec son nouveau Président, Anderson Ribeiro Correia, à la présence du Directeur des Relations Internationale: dans cette occasion, ils ont discuté de la possible réouverture de l’accord ICRANet-Capes et le Président du CAPES, ancien Recteur de l’ITA, a reconnu encore une fois l’importance d’ICRANet et ses activités au sein de l’ITA et de l’Université de Brasilia. Dans l’après midi, le Prof. Ruffini, auprès du Ministère brésilien de la science, de la technologie, de l’innovation et de la communication (MCTIC), a rencontré un de ses secrétaires principaux, l’Air Force Colonel Carlos Alberto Baptistucci. Ils ont discuté de la possibilité de nomination d’un diplômât pour le comité directif ICRANet, ainsi que un représentant du nouveau Ministère des Finances et/ou a membre de la communauté scientifique. Le Prof. Ruffini a rencontré aussi le Recteur de l’Université de Brasilia, la Prof. Marcia Abrahao, à la présence du Prof. Clovis Maia, de la Prof. Vanessa Andrade, du Prof. Marcos Maia et du Prof. Adalene Silva ; ils ont discuté la possibilité d’implémenter les activités d’ICRANet au sein de l’Université.

6. Intervention du Professeur Ruffini à “Science by Night”, Lycée Scientifique Galileo Galilei de Pescara, 19 Janvier 2019

Le 19 Janvier 2019, le Lycée Scientifique Galileo Galilei de Pescara, a organisé un important manifestation: “Science by Night”. Cet événement a crée des moments de rencontre entre les chercheurs et les citoyens, pour répandre la culture scientifique et la connaissances des métiers de la recherche et a eu une nombreuse participation, en offrant une opportunité unique pour prendre partie aux activités scientifiques visant à présenter soit le charme de la recherche en tant que métier, soit son impact social significatif. A cette occasion a pris partie une délégation ICRANet composée par le Prof. Remo Ruffini, le Prof. Gregory Vereshchagin et le Prof. She-Sheng Xue, invités pour présenter un important séminaire: “La fisica di Einstein applicata all'Universo. Aspetti concettuali, aspetti morali e sviluppi tecnologici”.

Pour voir l’entretien du Professeur Ruffini au canal TV Rete 8: https://www.youtube.com/watch?v=XjL2cA50LMk

7. Meeting du Professeur Ruffini avec le Directeur de l’ICTP et le Directeur exécutif du TWAS, Trieste, 31 Janvier 2019

Le 31 Janvier 2019, le Professeur Remo Ruffini a visité l’ICTP en Trieste et a rencontré le Directeur ICTP, le Prof. Fernando Quevedo, et le Directeur Exécutif du TWAS, le Prof. Romain Murenzi. Cette visite a représenté une intéressante opportunité pour discuter de la possible implémentation des synergies existants pour la performance de leur activités concernant les projets d’intérêt commun. La longue collaboration entre ICRANet et l’ICTP et l’ICRANet et le TWAS continuera a assurer une certaine stabilité aux activités de recherche en astrophysique relativiste, ò l’observation de l’univers du sous-sol, du sol et de l’espace.

De gauche à droite: le Prof. Fernando Quevedo (Directeur ICTP), le Prof. Remo Ruffini (Directeur ICRANet), le Prof. Romain Murenzi (Directeur Exécutif du TWAS) et le Prof. Sandro Scandolo (ICTP).

8. Visites scientifiques auprès du centre ICRANet de Pescara

9. Publications ICRANet jusqu’au 2018

Selon le SAO/NASA Astrophysics Data System (une bibliothèque électronique pour les chercheurs en astronomie et physique, exploitée par le Smithsonian Astrophysical Observatory (SAO) sous la NASA), les publications avec affiliation à ICRANet ont été 559 en 2018. Avec un nombre total de citations de 8845, il a résulté avoir un high impact measured by the H-index de 45. Entre les articles les plus cités on trouve “Electron-positron pairs in physics and astrophysics: From heavy nuclei to black holes”, publié sur Physics Reports en 2010, avec 253 citations. Ces informations sont disponible sur le site ICRANet: http://www.icranet.org/index.php?option=com_content&task=view&id=304&Itemid=780. Les publications des member de la Faculty ICRANet Faculty son disponible (soit in dans les bases de données NASA ADS, soit dans celles ArXiv : http://www.icranet.org/index.php?option=com_content&task=view&id=332&Itemid=806 both within NASA ADS and ArXiv databases.

10. Tradduction en russe du livre “Relativistic kinetic theory”, publié à Moscou

En Décembre 2018, a été publié la traduction russe du livre "Relativistic Kinetic Theory With Applications in Astrophysics and Cosmology", rédigé par l’ICRANet faculty member, Prof. Gregory Vereshchagin, en corédaction avec Alexey Aksenov de l’Institute of Computer Aided Design of the Russian Aacademy of Sciences, publié par Cambridge University Press en 2017. La publication de cette édition en russe a été soutenu grâce aux subventions de la Russian Foundation for Basic Research, project ID: 18-12-00027. Le livre a été publié avec la maison d'édition russe "Nauka" in Moscou.
Le livre est disponible au lien suivant:
https://naukabooks.ru/knigi/katalog/relyativistskaya_kineticheskaya_teoriya_s_prilozheniyami_v_astrofizike_i_kosmologii-_2018/

11. Publications récentes

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.



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.



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 k_BT ≤ 0.3 m_ec²) 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 k_BT ≥ 0.3 m_ec²) 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.



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, L_bol=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.



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.



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 E_c =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 E_p^-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