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2022
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Bulletin ICRANet
Février/Mars 2022



RÉSUMÉ
1. Communiqué de presse ICRA - ICRANet - CONICET - UNLP "One star could finally reveal the nature of what does lie at the Milky Way center"
2. GCN publiée par ICRANet, 25 Février 2022
3. Annonces importantes: le 80ème anniversaire du Prof. Remo Ruffini (Nice, 16 -18 Mai 2022) et le 6ème Bego Rencontre Summer School (Nice, 4 - 14 Juillet 2022)
4. Visite de S.E. Tsovinar Hambardzumyan, Ambassadeur d'Arménie en Italie, au centre ICRANet à Pescara, 16 Mars 2022
5. Nouveau protocole de coopération ICRANet - University of Western Cape (UWC), 1 Mars 2022
6. Nouveau protocole de coopération ICRANet - Sogang University, 28 Mars 2022
7. Renouvellement du protocole de coopération ICRANet - Institute of High Energy Physics within the Chinese Academy of Sciences (IHEP CAS), 7 Mars 2022
8. Podcast du Prof. Remo Ruffini "20 Mars 1916: Einstein publies la Théorie générale de la Relativité", Radio Storia La Repubblica, 20 Mars 2022
9. Publications récentes




1. Communiqé de presse ICRA - ICRANet - CONICET - UNLP "One star could finally reveal the nature of what does lie at the Milky Way center"

A new study deepens on the nature of the compact object sitting at our Galaxy center, SgrA*, by analyzing the astrometric data of one of the closest and long-studied stars that orbit around it. The international team of researchers from ICRA-ICRANet and CONICET-UNLP has found that besides the traditional black hole (BH) hypothesis, a dense concentration of dark matter (DM) made of fermions (called darkinos) can explain the detailed data (positions and velocities) of the star S2. The work provides a way to distinguish observationally between these two scenarios using the precession of the S2 orbit, very much in the same way that the theory of general relativity was proven using the precession of Mercury's orbit around the Sun. This new article, published in the Monthly Notices of the Royal Astronomical Society Letters1, holds relevant implications about the nature and mass of the dark matter particles.
For about three decades, two independent observational campaigns have monitored a cluster of young and bright stars orbiting the central parsec of our Galaxy to constrain the mass and nature of the massive object harbored at the center. These precise and accurate measurements have been possible thanks to the most powerful telescopes on earth. This achievement led to the Nobel Prize in Physics in 2020 awarded to Reinhard Genzel and Andrea Ghez: for the discovery of a supermassive compact object at the center of our galaxy.
Traditionally, a classical BH has been the most accepted hypothesis for the nature of SgrA*. The reason for this is that the orbits of the few detected S-stars are nearly perfect ellipses, implying the existence of a very compact object placed at its focus. Einstein's theory of general relativity predicts that the orbits cannot be Keplerian because there is a precession of the periapsis. The new work demonstrates that this effect is also present in the case of the DM core model and that its entity agrees with all publicly available data that shows the existence of this relativistic pattern in the S2 orbit. The article predicts that the two scenarios on the nature of SgrA* could be discriminated by measuring the precession of S2 around the next apocenter passage that will occur in 2026. The reason behind this difference is that while the BH predicts a unique prograde precession, in the DM scenario, it can be either retrograde or prograde, depending on the amount of DM filling the orbit, which depends on the mass of the darkinos.
A remarkable aspect of this novel DM interpretation of SgrA* is that the DM distribution is not constrained to the core of the Galaxy. The DM configuration extends to the outskirts of the Galaxy, forming a dilute halo that explains the circular velocity of far away objects as welll!. This result, together with a related study (see https://twitter.com/RAS_Journals/status/1489539729037008899?ref_src=twsrc%5Etfw) obtained by some of the research team, hints towards a paradigm shift in the field of DM halos and supermassive BH formation. It suggests that non-active galaxies as our own host dense DM concentrations at their centers, while more massive and active-galaxies, host supermassive BHs that has been formed from the gravitational collapse of these DM cores.


FIG. 1. Figure taken from [1] with the kind permission of the authors. Relativistic precession of S2 in the projected orbit on the plane of the sky as predicted in the BH and RAR DM models. While it is prograde for the BH and RAR (m = 58 keV/c2) (in dashed black and green respectively), it is retrograde for the RAR DM model (m = 56 keV/c2) (in dashed red). The solid (theoretical) curves and gray (data) points correspond to the first period (≈ 1994-2010) while the dashed (theoretical) curves and cyan (data) points to the second period (≈ 2010-2026). Right panels: zoom of the region around apocentre (top panel) and pericentre (bottom panel). The astrometric measurements are taken from Do et al.2.



FIG. 2. Relativistic precession of S2 as manifested in the right ascension as a function of time after last pericentre passage, where effects are more prominent. BH model (Left panel) and RAR model for m = 56 keV/c2 (Right panel).

Communiqué de presse sur le site ICRANet: http://www.icranet.org/communication/
Communiqué de presse sur Oxford University press: https://oxfordjournals.altmetric.com/details/113891044
Communiqué de presse sur Conicet-Argentina: https://laplata.conicet.gov.ar/un-nuevo-paso-para-desentranar-que-hay-en-el-centro-de-la-via-lactea/
Upcoming S2-star astrometry could potentially establish if SgrA* is governed by a classical BH or by a quantum DM system: read more in a paper just published in MNRAS (Argüelles et al) at https://t.co/Wbx3kSMokD . #SagittariusA* #darkmatter #darkinos #fermions #blackholes pic.twitter.com/lWMz7d5l8D
— RAS Journals (@RAS_Journals) February 4, 2022


------------
1 C. R. Argüelles, M. F. Mestre, E. A. Becerra-Vergara, V. Crespi, A. Krut, J. A. Rueda, and R. Ruffini, Monthly Notices of the Royal Astronomical Society: Letters 511, L35 (2021), arXiv:2109.10729, URL https://doi.org/10.1093/mnrasl/slab126.
2 T. Do, A. Hees, A. Ghez, G. D. Martinez, D. S. Chu, S. Jia, S. Sakai, J. R. Lu, A. K. Gautam, K. K. O'Neil, et al., Science 365, 664 (2019), 1907.10731.



2. GCN publiée par ICRANet, 25 Février 2022

TITLE: GCN CIRCULAR
NUMBER: 31648
SUBJECT: GRB 220101A: The first example of a Petanova
DATE: 22/02/25 11:38:50 GMT
FROM: Remo Ruffini at ICRA ruffini@icra.it

R. Ruffini, Y. Aimuratov, L. Becerra, C.L. Bianco, Y-C. Chen, C. Cherubini, Y.F. Cai, S. Eslamzadeh, S. Filippi, M. Karlica, Liang Li, G.J. Mathews, R. Moradi, M. Muccino, G.B, Pisani, F. Rastegar Nia, J.A. Rueda, N. Sahakyan, Y. Wang, S.S. Xue, Y.F. Yuan, Y.L. Zheng, on behalf of ICRA, ICRANet and USTC team, report:
We confirm the results of our previous GCN (Ruffini et al. 2022, GCN 31465). Following the release of the X-ray afterglow (Tohuvavohu et al. 2022, GCN 31347) and the GeV data (Arimoto et al. 2022, GCN 31350) of this source, we can estimate the total (keV+MeV+GeV) isotropic energy (see e.g. Ruffini et al. 2021, MNRAS 504, 5301) to be ~6E54 erg, making this GRB the most powerful GRB in 26 years (a "Petanova"). The period of the new neutron star (see e.g. Ruffini et al. 2021, MNRAS 504, 5301) generating the X-ray afterglow is ~1 ms, the initial mass of the BH (see e.g. Ruffini et al. 2019 ApJ 886, 82) is 6.15 solar mass, the spin parameter is 0.95, and the irreducible mass is 4.98 solar masses (see Fig. 1). The peak of the bolometric flux of supernova is of the order of 1E-17 erg/s/cm^2 and will appear in 73+/-15 days after the GRB trigger, with emissions lasting ~ one month peaking in different infrared bands. The observational follow up of this source is encouraged.
Fig. 1: http://www.icranet.org/docs/GRB220101A.pdf



3. Annonces importantes: le 80ème anniversaire du Prof. Remo Ruffini (Nice, 16 -18 Mai 2022) et le 6ème Bego Rencontre Summer School (Nice, 4 - 14 Juillet 2022)

Le 80ème anniversaire du Prof. Remo Ruffini
Nous sommes très heureux de vous inviter à participer aux célébrations du 80ème anniversaire du Prof. Remo Ruffini, le 17 Mai 2022, qui auront lieu du 16 au 18 Mai 2022 auprès du Siège ICRANet à Villa Ratti à Nice (France). Il s'agira d'une conférence hybride, soit en personne qu'en ligne.
Félicitations, salutations et présentations scientifiques seront bienvenues.
Le lien à la plateforme Indico sera publié, dès que disponible, sur le site web d'ICRANet (http://www.icranet.org/).

Le 6ème Bego Rencontre Summer School
Nous sommes heureux de vous informer que du 4 au 14 Juillet 2022, l'ICRANet est en train d'organiser le "6ème Bego Rencontre" auprès du Siège ICRANet à Villa Ratti à Nice.
Les sujets principaux qui seront abordés pendent cette école d'été couvrent la distribution de la matière sombre dans l'Univers, la physique de notre centre galactique, l'extraction d'énergie rotationnelle d'un Trous Noir de Kerr dans les Sursauts Gamma (GRBs) et dans les Noyaux galactiques actifs (AGNs), les domaines associés du Quantum et de l'électrodynamique classique, les Étoiles à neutrons, les Naines blanches, les mesures de précision de la Relativité Générale et les Ondes gravitationnelles.
Votre participation sur ces sujets sera appréciée. La liste des conférenciers ainsi que plus de détails et le lien à la plateforme Indico seront publiés, dès que disponibles, sur le site web d'ICRANet (http://www.icranet.org/).



4. Visite de S.E. Tsovinar Hambardzumyan, Ambassadeur d'Arménie en Italie, au centre ICRANet à Pescara, 16 Mars 2022

Le 16 Mars 2022, l' ambassadeur extraordinaire et plénipotentiaire de la République d'Arménie en Italie, S. E. Tsovinar Hambardzumyan et son assistante Dr Naira Ghazaryan, ont visité le centre ICRANet de Pescara.
Le Prof. Remo Ruffini, Directeur d'ICRANet, a présenté le centre ainsi que sa bibliothèque et ses précieux livres, tableaux et documents y gardés. Le Prof. Ruffini a aussi illustré les activité courantes, les principaux thèmes de recherche et les résultats obtenus. Il a également présenté les projets réalisés par le centre ICRANet à Pescara et ses collaborations. Le rôle important joué par ICRANet dans la promotion quotidienne des échanges scientifiques ainsi que dans l'établissement d'accords de coopération avec les principaux Universités et Institut de recherche dans le monde, a été aussi mis en relief et discuté.

Fig. 3, 4 et 5: Prof. Ruffini, Directeur d'ICRANet, en train de présenter le centre ICRANet à S.E. Tsovinar Hambardzumyan, Ambassadeur de la République d'Arménie en Italie, 16 Mars 2022.

Le Prof. Narek Sahakyan, Directeur du Siège ICRANet en Arménie, a participé à la visite via GoToMeeting et a présenté et remarqué l'importance et le rôle joué par le centre ICRANet en Arménie en ce qui concerne l'élargissement des activités d'ICRANet dans le panorama international. Les deux parties ont aussi souligné l'importance de la coopération scientifique entre Italie-Arménie dans le domaine de l'astrophysique ont discuté des possibles de développement et élargissement ultérieur de la collaboration scientifique entre les deux pays.

Fig. 6: Le Prof. Ruffini pendant son meeting bilatéral avec S.E. Tsovinar Hambardzumyan, Ambassadeur de la République d'Arménie en Italie, 16 Mars 2022. Fig. 7: Le Prof. Narek Sahakyan, Directeur du Siège ICRANet en Arménie, pendant son meeting via GoToMeeting avec l'Ambassadeur Hambardzumyan, 16 Mars 2022.

Cette nouvelle a été aussi publiée sur la page officielle Facebook de l'Ambassade de la République d'Arménie en Italie, disponible au lien suivant: https://www.facebook.com/HayastaniDespanutyun/



5. Nouveau protocole de coopération ICRANet - University of Western Cape (UWC), 1 Mars 2022

Le 1 Mars 2022, l'ICRANet a signé un nouveau protocole de coopération avec l'Université de Western Cape (UWC) en Afrique du Sud. Ce protocole a été signé par le Prof. Tyrone Brian Pretorius (Recteur de l'UWC), par le Prof. Roy Marteens (Prof. en Astronomie et Astrophysique a l'UWC), par le Prof. Remo Ruffini (Directeur d'ICRANet) et par le Prof. Narek Sahakyan (Directeur du Siège ICRANet en Arménie).


Ce protocole demeurera valide pour 5 années et 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.
Pour le texte du protocole: http://www.icranet.org/index.php?option=com_content&task=view&id=1411



6. Nouveau protocole de coopération ICRANet - Sogang University, 28 Mars 2022


Le 28 Mars 2022, l'ICRANet a signé un nouveau protocole de coopération avec l'Université Sogang en Corée du Sud. Ce protocole a été signé par le Prof. Luke Sim Jong-Hyeok SJ (Président de l'Université Sogang), par le Prof. Stefano Scopel (Directeur du CQUeST, Université Sogang), par le Prof. Remo Ruffini (Directeur d'ICRANet) et par le Prof. Carlo Luciano Bianco (Professeur de la Faculté d'ICRANet).
Ce protocole demeurera valide pour 5 années et 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.
Pour le texte du protocole: http://www.icranet.org/index.php?option=com_content&task=view&id=1414



7. Renouvellement du protocole de coopération ICRANet - Institute of High Energy Physics within the Chinese Academy of Sciences (IHEP CAS), 7 Mars 2022


Le 7 Mars 2022 a été renouvelé le Protocol de Coopération entre l'ICRANet et l'Institute of High Energy Physics within the Chinese Academy of Sciences (IHEP CAS). Le renouvellement a été signé par le Prof. Shuang-Nan Zhang (Directeur du Key Laboratory of Particle Astrophysics à l'IHEP CAS) et par le Prof. Remo Ruffini (Directeur d'ICRANet). Cet accord demeurera valide pour 5 années et 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.
Pour le texte du protocole: http://www.icranet.org/ihep



8. Podcast du Prof. Remo Ruffini "20 Mars 1916: Einstein publies la Théorie générale de la Relativité", Radio Storia La Repubblica, 20 Mars 2022

Le 20 Mars 2022 le canal web Radio Storia de La Repubblica, un de plus importants quotidiens en Italie, a publié un podcast registré par le Prof. Remo Ruffini, Directeur d'ICRANet.
Le podcast, titré "20 Mars 1916: Einstein publies la Théorie générale de la Relativité" a été dirigé par le journaliste italien Francesco De Leo et abordait des importants événements historiques, comme s'ils venaient de se passer. Ce podcast a été réalise come si on vivait le jour du 20 Mars 1916, quand Albert Einstein venait de publier sa Théorie générale de la relativité dans les Annals of Physics n° 7. Dans cet article, Einstein illustrait l'équation qui indique la force gravitationnelle en tant que courbure de l'espace-temps et ça représentait un des combinaisons les plus impressionnantes entre philosophie, intuition physique et habilités mathématiques.
Le Prof. Ruffini a été invité à commenter cet article, pour mieux comprendre son importance et son influence sur la relativité générale avec la théorie de la gravitation de Einstein. Le Prof. Ruffini a remarqué que cet article est un texte très importante, puisque dans son travail, Einstein reprends et généralise la théorie de la relativité et commence à la définir comme théorie spéciale de la relativité. Il nous rappelle qu'une des contributions les plus importants dans ce domaine a été le travail de Hermann Minkowski, qui reconnaissait l'équivalence formelle entre les coordonnés de l'espace et du temps et les rend accessibles pour la construction de cette théorie. Einstein explantait le formalisme mathématique de Tullio Levi Civita et de Matteo Ricci, et enfin il obtenait l'équation du champ et de la relativité générale. Il a montré que, si un rayon de lumière passe proche au Soleil, il pourrait y avoir la déflection du rayon de lumière due au champs gravitationnel du Soleil et ça se passe aussi pour un signal lumineux qui passe proche à un planète. Cette vision changeait totalement la physique traditionnelle newtonienne, qui affirmait qu'un rayon de lumière se propage en ligne droite. Einstein espérait aussi que la lumière provenant d'une étoile doit changer la fréquence de son mouvement en s'écartant de l'étoile, indiquant le glissement vers longueurs d'onde plus longue: ça c'est aussi un autre concept totalement différent de celui envisagé par Newton. En outré, au temps de Newton et de Kepler, l'astronomie classique concevait le mouvement comme un mouvement en ellipse; Einstein, en 1916, a affirmé qu'il y avait une petite quantité qui modifie ce mouvement et a prévu un mouvement "a rosetta" de 43 arc secondes par siècle: ça c'est une petite quantité, mais c'est conceptuellement révolutionnaire.
En commentant l'article de Einstein, le Prof. Ruffini a aussi expliqué que, comme affirmait aussi Einstein même, il n'existe pas "le temps" mais il y ont 3 composants spatiales et un composant temporel qui travaillent ensemble, comme aussi décrit par Minkowski. Donc, depuis lors, la physique n'a plus été une théorie avec 1 or 3 composants, mais comme une théorie formée par l'interaction de 4 dimensions. Einstein disait qu'il n'y a pas "le temps" mais il existe l'espace-temps, décrit par la métrique introduite par Tullio Levi Civita et Matteo Ricci: tout ça représentait une grande révolution conceptuelle qui est à l'origine d'une nouvelle physique, des nouvelles observations ainsi que d'une nouvelle connaissance.
Pour écouter le podcast (en Italien): https://www.repubblica.it/podcast/storie/radio-storia/stagione1/



9. Publications récentes

Rueda, J. A.; Ruffini, R.; Kerr, R. P., Gravitomagnetic interaction of a Kerr black hole with a magnetic field as the source of the jetted GeV radiation of gamma-ray bursts, The Astrophysical Journal; in press.
We show that the gravitomagnetic interaction of a Kerr black hole (BH) with a surrounding magnetic field induces an electric field that accelerates charged particles to ultra-relativistic energies in the vicinity of the BH. Along the BH rotation axis, these electrons/protons can reach energies of even thousands of PeV, so stellar-mass BHs in long gamma-ray bursts (GRBs) and supermassive BHs in active galactic nuclei (AGN) can contribute to the ultrahigh-energy cosmic rays (UHECRs) thorough this mechanism. At off-axis latitudes, the particles accelerate to energies of hundreds of GeV and emit synchrotron radiation at GeV energies. This process occurs within 60° around the BH rotation axis, and due to the equatorial-symmetry, it forms a double-cone emission. We outline the theoretical framework describing these acceleration and radiation processes, how they extract the rotational energy of the Kerr BH and the consequences for the astrophysics of GRBs.
Link preprint: https://arxiv.org/abs/2203.03471


C. R. Argüelles, E. A. Becerra-Vergara, A. Krut, R. Yunis, J. A. Rueda and R. Ruffini, Reshaping our understanding on structure formation with the quantum nature of the dark matter, published on International Journal of Modern Physics D Vol. 31, No. 02, 2230002 (2022).
We study the nonlinear structure formation in cosmology accounting for the quantum nature of the dark matter (DM) particles in the initial conditions at decoupling, as well as in the relaxation and stability of the DM halos. Different from cosmological N-body simulations, we use a thermodynamic approach for collisionless systems of self-gravitating fermions in general relativity, in which the halos reach the steady state by maximizing a coarse-grained entropy. We show the ability of this approach to provide answers to crucial open problems in cosmology, among others: the mass and nature of the DM particle, the formation and nature of supermassive black holes in the early Universe, the nature of the intermediate mass black holes in small halos, and the core-cusp problem.
DOI: https://doi.org/10.1142/S0218271822300026


Gregory Vereshchagin, Liang Li, Damien Bégué, Is magnetically dominated outflow required to explain GRBs?, published on Monthly Notices of the Royal Astronomical Society, stac757, on March 22, 2022.
The composition of relativistic outflows producing gamma-ray bursts is a long standing open question. One of the main arguments in favour of magnetically dominated outflows is the absence of photospheric component in their broadband time resolved spectra, with such notable example as GRB 080916C. Here, we perform a time-resolved analysis of this burst and confirm the previous detection of an additional spectral component. We show that this subdominant component is consistent with the photosphere of ultrarelativistic baryonic outflow, deep in the coasting regime. We argue that, contrary to previous statements, the magnetic dominance of the outflow is not required for the interpretation of this GRB. Moreover, simultaneous detection of high energy emission in its prompt phase requires departure from a one-zone emission model.
DOI: https://doi.org/10.1093/mnras/stac757


MAGIC collaboration, Combined searches for dark matter in dwarf spheroidal galaxies observed with the MAGIC telescopes, including new data from Coma Berenices and Draco, published in Physics of the Dark Universe, Volume 35, March 2022, 100912.
Milky Way dwarf spheroidal galaxies (dSphs) are among the best candidates to search for signals of dark matter annihilation with Imaging Atmospheric Cherenkov Telescopes, given their high mass-to-light ratios and the fact that they are free of astrophysical gamma-ray emitting sources. Since 2011, MAGIC has performed a multi-year observation program in search for Weakly Interacting Massive Particles (WIMPs) in dSphs. Results on the observations of Segue 1 and Ursa Major II dSphs have already been published and include some of the most stringent upper limits (ULs) on the velocity-averaged cross-section σann v of WIMP annihilation from observations of dSphs. In this work, we report on the analyses of 52.1 h of data of Draco dSph and 49.5 h of Coma Berenices dSph observed with the MAGIC telescopes in 2018 and in 2019 respectively. No hint of a signal has been detected from either of these targets and new constraints on the σann v of WIMP candidates have been derived. In order to improve the sensitivity of the search and reduce the effect of the systematic uncertainties due to the -factor estimates, we have combined the data of all dSphs observed with the MAGIC telescopes. Using 354.3 h of dSphs good quality data, 95% CL ULs on σann v have been obtained for 9 annihilation channels. For most of the channels, these results reach values of the order of 10-24 cm3/s at ∼ 1 TeV and are the most stringent limits obtained with the MAGIC telescopes so far.
DOI: https://doi.org/10.1016/j.dark.2021.100912


MAGIC collaboration, Investigating the Blazar TXS 0506+056 through Sharp Multiwavelength Eyes During 2017-2019, published on The Astrophysical Journal, Volume 927, Issue 2, id.197.
The blazar TXS 0506+056 got into the spotlight of the astrophysical community in 2017 September, when a high-energy neutrino detected by IceCube (IceCube-170922A) was associated at the 3σ level with a γ-ray flare from this source. This multi-messenger photon-neutrino association remains, as per today, the most significant association ever observed. TXS 0506+056 was a poorly studied object before the IceCube-170922A event. To better characterize its broadband emission, we organized a multiwavelength campaign lasting 16 months (2017 November to 2019 February), covering the radio band (Metsähovi, OVRO), the optical/UV (ASAS-SN, KVA, REM, Swift/UVOT), the X-rays (Swift/XRT, NuSTAR), the high-energy γ rays (Fermi/LAT), and the very high-energy (VHE) γ rays (MAGIC). In γ rays, the behavior of the source was significantly different from the behavior in 2017: MAGIC observations show the presence of flaring activity during 2018 December, while the source only shows an excess at the 4σ level during the rest of the campaign (74 hr of accumulated exposure); Fermi/LAT observations show several short (on a timescale of days to a week) flares, different from the long-term brightening of 2017. No significant flares are detected at lower energies. The radio light curve shows an increasing flux trend that is not seen in other wavelengths. We model the multiwavelength spectral energy distributions in a lepto-hadronic scenario, in which the hadronic emission emerges as Bethe-Heitler and pion-decay cascade in the X-rays and VHE γ rays. According to the model presented here, the 2018 December γ-ray flare was connected to a neutrino emission that was too brief and not bright enough to be detected by current neutrino instruments.
DOI: https://doi.org/10.3847/1538-4357/ac531d


MAGIC collaboration, Multiwavelength study of the gravitationally lensed blazar QSO B0218+357 between 2016 and 2020, published on Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 2.
We report multiwavelength observations of the gravitationally lensed blazar QSO B0218+357 in 2016-2020. Optical, X-ray, and GeV flares were detected. The contemporaneous MAGIC observations do not show significant very high energy (VHE; ≳100 GeV) gamma-ray emission. The lack of enhancement in radio emission measured by The Owens Valley Radio Observatory indicates the multizone nature of the emission from this object. We constrain the VHE duty cycle of the source to be <16 2014-like flares per year (95 per cent confidence). For the first time for this source, a broad-band low-state spectral energy distribution is constructed with a deep exposure up to the VHE range. A flux upper limit on the low-state VHE gamma-ray emission of an order of magnitude below that of the 2014 flare is determined. The X-ray data are used to fit the column density of (8.10 ± 0.93stat) × 1021 cm-2 of the dust in the lensing galaxy. VLBI observations show a clear radio core and jet components in both lensed images, yet no significant movement of the components is seen. The radio measurements are used to model the source-lens-observer geometry and determine the magnifications and time delays for both components. The quiescent emission is modelled with the high-energy bump explained as a combination of synchrotron-self-Compton and external Compton emission from a region located outside of the broad-line region. The bulk of the low-energy emission is explained as originating from a tens-of-parsecs scale jet.
DOI: https://doi.org/10.1093/mnras/stab3454


Behzad Eslam Panah, and Khadijie Jafarzade, Thermal stability, P−V criticality and heat engine of charged rotating accelerating black holes, General Relativity and Gravitation. 54 (2022) 19
In this paper, we study thermodynamic features of the charged rotating accelerating black holes in anti-de Sitter spacetime. First, we consider these black holes as the thermodynamic systems and analyze thermal stability/instability through the use of heat capacity in the canonical ensemble. We also investigate the effects of angular momentum, electric charge and string tension on the thermodynamic quantities and stability of the system. Considering the known relation between pressure and the cosmological constant, we extract the critical quantities and discuss how the mentioned parameters affect them. Then, we construct a heat engine by taking into account this black hole as the working substance, and obtain the heat engine efficiency by considering a rectangle heat cycle in the P−V plane. We examine the effects of black hole parameters on the efficiency and analyze their effective roles. Finally, by comparing the engine efficiency with Carnot efficiency, we investigate conditions in order to have a consistent thermodynamic second law.
DOI: https://doi.org/10.1007/s10714-022-02904-9


Tayyebeh Yazdizadeh, Gholam Hossein Bordbar, and Behzad Eslam Panah, The structure of hybrid neutron star in Einstein-Λ gravity, Physics of the Dark Universe 35 (2022) 100982.
In this paper, we investigate the structure of neutron stars by considering both the effects of the cosmological constant and the existence of quark matter for neutron stars in Einstein's gravity. For this purpose, we use a suitable equation of state (EoS) which includes a layer of hadronic matter, a mixed phase of quarks and hadrons, and a quark matter in the core. To investigate the effect of the cosmological constant on the structure of hybrid neutron stars, we utilize the modified TOV equation in Einstein -Λ gravity. Then we derive the mass-radius relation for different values of the cosmological constant. Our results show that for small values of the cosmological constant (Λ), especially for the cosmological constant from the cosmological perspective (Λ=10−52m−2),Λ has no significant effect on the structure of hybrid neutron stars. But for higher values, for example, by considering Λ>10−14 m−2, this quantity affects the maximum mass and radius of these stars. We find an upper limit for the cosmological constant as Λ<9×10−13m−2, based on the fact that the gravitational redshift cannot be more than 1 for stars. The maximum mass and radius of these stars decrease by increasing the cosmological constant Λ. Also, by determining and analyzing radius, the compactness, Kretschmann scalar, and gravitational red shift of the hybrid neutron stars with M=1.4M⊙ in the presence of the cosmological constant, we find that by increasing Λ, they are contracted. Also, our results for dynamical stability show that these stars satisfy this condition.
DOI: https://doi.org/10.1016/j.dark.2022.100982
 
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