| Newsletter English February – September 2024 |
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  ICRANet Newsletter
ICRANet Newsletter
February - September 2024
SUMMARY
1. ICRA – ICRANet press release “Discovering Early Gamma-Ray Burst Emissions with Cosmological Time Dilation”, May 9, 2024 2. The 6th Galileo-Xu Guangqi meeting (GX6), April 19-24, Hengyang (China) 3. The 17th Marcel Grossmann meeting (MG17), July 7-12, Pescara (Italy) 4. The European Researchers' Night, September 27, 2024 5. Upcoming meeting: the “3rd Julio Garavito Armero meeting”, November 13-15, 2024, Bucaramanga (Colombia) 6. Seminar by Prof. Ruffini “The first of the seven Episodes of BdHNe”, May 17, 2024, Princeton University (USA) 7.Seminar by Prof. Gregory Vereshchagin and Prof. Mikalai Prakapenia “Pair creation in hot electrosphere of compact astrophysical objects”, February 8, 2024, ICRANet center in Pescara, (Italy) 8. Seminar by Prof. Ruffini “The role of Black Holes in the Universe”, September 12, 2024, Nice (France) 9. ICRANet participation at the conference “Black Holes & Cosmology” (BHCos 2024), March 11-15, 2024, Nassau (Bahamas) 10. ICRANet participation at the “Planetarium day 2024”, March 17, 2024, Ortona (Italy) 11. ICRANet participation at the “35th Tehran International Book Fair (TIBF)”, May 8-18, 2024 12.ICRANet participation at the “45th COSPAR Scientific Assembly”, July 13-21, 2024, Busan (South Korea) 13. ICRANet participation at the “XXIV Gamow International Astronomical Conference”, August 19-23, 2024, Odessa (Ukraine) 14. ICRANet press release “Aurora predicted for the dawn of Saturday 11 may also in Italy”, May 11, 2024 15. Prof. Ruffini meeting with the President of Abruzzo Region, September 16, 2024 16. Pubblicazioni recenti 17. ICRANet participation at the Chinese reception, September 17, 2024 18. ICRANet participation at the Armenian reception, September 25, 2024 19. Prof. Ruffini among the top 2% of the most cited authors, according to Elsevier 20. Publication of the 5th Zeldovich meeting proceedings, February 25, 2024 21. Publication of “Remo Ruffini Festschrift”, June 24, 2024 22. Publication of the article “From “introducing the black hole” (1971) to the discoveries of an alive black hole in GRB 190114C (2021) a collection of documents prepared in occasion of the 17th Italo-Korean meeting”, September 6, 2024 23. Three conferences on the 2024 leap year “Julius Caesar's algorithm and Gregory XIII’s algorithm”, February 2024 24. “Total eclipse at Solar Maximum”, observations and conference, April 6-8, 2024 25. 2024 Gerbertus’ day: X-ray solar flares, Coronal Mass Ejections and Aurorae, May 11-12, 2024 26. New “Convention de partenariat” between ICRANet and the Municipality of Nice”, April 22, 2024 27. Renewal of the cooperation protocol between ICRANet and the Al-Farabi Kazakh National University (KAZNU), May 2, 2024 28. New cooperation protocol between ICRANet and the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A), July 19, 2024 29. Prof. Ruffini awarded the prize “Federico Valignani”, August 9, 2024, Torrevecchia Teatina (Italy) 30. Joint Call for Proposals “BRFFR - ICRANet 2025” 31. Visit of Librorio Stuppia, Rector of the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A), , at the ICRANet center in Pescara, March 25, 2024, Pescara (Italy) 32. Scientific visits to ICRANet 33. Recent publications
1.ICRA – ICRANet press release “Discovering Early Gamma-Ray Burst Emissions with Cosmological Time Dilation”, May 9, 2024
Gamma-ray bursts (GRBs), in a few seconds, release luminosities (in gamma-rays) comparable to the luminosity of all stars in the observable Universe, which makes them detectable to the dawn of galaxy and stellar formation. The repointing time of the XRT instrument onboard the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying GRB early X-ray emissions within ≈ 40 s after a GRB trigger by gamma-ray detectors. To address this issue, a team of scientists from ICRA and ICRANet adopted a novel approach that capitalizes on the cosmological time dilation in GRBs at the furthest boundaries of the observable Universe (with a cosmological redshift z ranging up to ∼ 9, i.e., only ∼ 500 million years after the big bang) and analyzed all the 368 GRBs with a measured distance in the Swift GRB catalog from the year 2005 until December 31st, 2023. This allowed to unveil the early X-ray emission in more than 220 GRBs and to validate the observation of the collapse of the carbon-oxygen (CO) core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. For three prototypical BdHNe I, it is shown the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-optical-radio synchrotron afterglow emission: a brief gravitational wave signal may separate the two stages due to a fast-spinning νNS triaxial-to-axisymmetric transition. By analyzing the long GRB redshift distribution for the different BdHN types, it is inferred that BdHNe II and BdHNe III may originate the NS binary progenitors of short GRBs. The paper has been published by The Astrophysical Journal on May 9th, 2024.
Important astronomical breakthroughs are often marked by the possibility of studying events occurring in the nearby Universe. On the contrary, in this work, it is presented how the observation of GRBs at a very high cosmological distance, by exploiting the cosmological time dilatation factor (1 + z) as a novel observational tool, can allow to enter the terra incognita of the very early GRB X-ray emission. This emission is currently inaccessible to the Swift/XRT detector in nearby events, which paradoxically would be more suitable to be studied: the significant instrumental delay of repointing the Swift/XRT detector following the GRB trigger, always bigger than ∼ 40 s expressed in the observer’s rest frame, prevents their early X-ray emission observations. However, due to the cosmological time dilation, a time interval ∆t measured on Earth corresponds to a time interval ∆t/(1 + z) in the cosmological source rest-frame, where z is its cosmological redshift. In other words, a phenomenon appearing to our instruments on the Earth to last 50 s may last 10 s if the source is at z = 4, like if we were observing the phenomenon in slow motion. Therefore, the time needed by Swift/XRT to start its observations after the GRB trigger may correspond to a much shorter actual time for sources with a large redshift z, exactly by a factor (1 + z). If, e.g., Swift/XRT starts to observe a GRB 60 s after the trigger in the observer frame, it is observing the X-ray signals emitted 60/(1 + z) s after the trigger in the cosmological rest-frame of the source. This corresponds to the possibility of observing 10 s after the trigger for a GRB with z = 5: the higher the GRB redshift, the shorter the time Swift/XRT can observe the source after the GRB trigger. This is clearly shown in Fig. 1 where it is presented the observational XRT time delays for all the 368 GRBs analyzed in the observer frame (upper panel) and the cosmological rest frame of each source (lower panel) as a function of their cosmological redshifts z. The green dotted line marks the 43.88 s minimum time delay in both panels, and the red dashed line in the bottom panel corresponds to this minimum delay rescaled as a function of the redshift of the source: 43.88/(1 + z) s. More than 220 sources, which were observed by Swift/XRT with a delay greater than 43.88 s, would not have been deemed interesting from the early X-ray emission point of view. However, thanks to their large cosmological redshift, when looking at their cosmological rest frames, it is clear that they have been observed less than 40 s after the trigger. This new methodology allows the analysis of the very early transient X-ray regimes in GRB afterglows, which pose a stringent test for all GRB theoretical models. Within the context of the binary-driven hypernova (BdHN) model, it is applied to three BdHNe I at high redshift: GRB 090423 at z = 8.233, GRB 090429B at z ≈ 9.4, and GRB 220101A at z = 4.61. The cosmological time dilation enables observing the very early X-ray afterglow emission in these three GRBs (see, e.g., Fig. 2 and Fig. 3). It is thus validated the observation of the collapse of the carbon-oxygen (CO) core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the BdHN scenario. It is also evidenced by the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-optical-radio synchrotron afterglow emission. A brief gravitational wave signal may separate the two stages due to a fast-spinning νNS triaxial-to-axisymmetric transition. Equally important is the byproduct of analyzing the redshift distribution of all the 368 GRBs of the sample within the BdHN model. The similarity between the redshift distribution of BdHNe II and BdHNe III and that of short GRBs supports the hypothesis that the BdHNe II and BdHNe III remnants, after evolving into binary NS systems, could later become progenitors of short GRBs. This unique prediction of the BdHN scenario deserves further attention from an observational and a theoretical point of view. Indeed, new missions with wide field-of-view soft X-ray instruments designed to simultaneously observe the GRB X-ray and gamma-ray emissions from the moment of the GRB trigger without any time delay, such as the THESEUS and HERMES missions, present a great opportunity. For more information:
Contact: Prof. Remo Ruffini, Director, ICRANet | Phone: (+39) 085 2305 4201 | mobile: (+39) 339 475 2566 | E-mail: ruffini@icra.it
Reference article:
Probing electromagnetic-gravitational wave emission coincidence in a type I binary-driven hypernova family of long GRBs at very-high redshift"C.L. Bianco, M.T. Mirtorabi, R. Moradi, F. Rastegarnia, J.A. Rueda, R. Ruffini, Y. Wang, M. Della Valle, L. Li, S.R. Zhang; ApJ, 966 (2024) 219; DOI:https://doi.org/10.3847/1538-4357/ad2fa9
Press release on ICRANet website:https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
2.The 6th Galileo-Xu Guangqi meeting (GX6), April 19-24, Hengyang (China)
From April 19-24, 2024, ICRANet has organized the 6th Galileo-Xu Guangqi Meeting (GX6) in Hengyang, China. This meeting has been organized in conjunction with the 2024 Annual Meeting of the Division of Gravitation and Relativistic Astrophysics of the Chinese Physical Society, the most important gravity-related conference in China. These two meetings have been hosted jointly by the University of South China, the Hunan Normal University, the Lanzhou University, the Institute of Theoretical Physics at the Chinese Academy of Sciences (CAS), the Hunan University of Arts and Sciences, and the Purple Mountain Observatory of CAS.
Both these conferences provided a platform for researchers to communicate their new discoveries and latest progresses in the fields of gravitation and relativistic astrophysics. The contents will cover but are not limited to classical and quantum gravity theories, gravity experiments, black hole physics, gravitational waves, nuclear astrophysics, dark matter and dark energy, multi-messenger astronomy, and cosmology, and other cutting-edge scientific problems. Over 700 international scientists attended this 5 days meeting, coming in particular from Asia.
On the occasion of the GX6 meeting, a dinner was offered in honor of Prof. Ruffini by the Mayor of Hengyang (a city with 9 millions of inhabitants and 20 Universities) Mr Zhu Jian. Presents at the dinner were also the Secretary Liu Yue-Gao and 3 members of the Chinese Academy of Sciences: Rong-Gen Cai, Wu Yue-Liang and Ouyang Zhong-Can and Prof. Wenbin Lin, local organizer of the GX6 meeting.
The meetings’ website: http://meeting2024.usc.edu.cn/english/Meeting_english/conferences/gr24/index.php
Press releases on the event: https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
3.The 17th Marcel Grossmann meeting (MG17), July 7-12, Pescara (Italy)
The 17th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories (MG17) took place at Aurum as well as at the University Gabriele d’Annunzio of Chieti-Pescara (Ud’A) in Pescara - Italy, from July 7 to 12, 2024. MG17 meeting has been co-organized by ICRA and ICRANet, in collaboration with the Municipality of Pescara and Ud’A.
More than 700 participants from 45 different countries, joined the conference and presented the most relevant recent results on the understanding of the Universe, achieved thanks to Albert Einstein’s equations of general relativity. Thanks to the financial support provided by IUPAP a lot of scientists from developing countries had also the possibility to attend the conference. The rich program of the conference was articulated in 41 plenary presentations, 3 public lectures and 64 parallel session, for a total of 631 scientific contributions. The meeting exceeded every expectation and confirmed once again its world leading role in the field of Relativistic Astrophysics, developed in the years since 1985 by ICRA at Sapienza University, and, in the most recent years, thanks to the collaboration with ICRANet center in Pescara.
Since 1975, the Marcel Grossmann Meetings (on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories) have been organized in order to provide opportunities for discussing recent advances in gravitation, general relativity and relativistic field theories, emphasizing mathematical foundations, physical predictions and experimental tests. The objective of these meetings is to elicit exchange among scientists that may deepen our understanding of spacetime structures as well as to review the status of ongoing experiments aimed at testing Einstein's theory of gravitation either from the ground or from space. Previous meetings have been held in Trieste (MG1: 1975, MG2: 1979), Shanghai (MG3: 1982), Rome (MG4: 1985, MG9: 2000, MG14: 2015, MG15: 2018), Perth (MG5: 1988), Kyoto (MG6: 1991), Stanford (MG7: 1994), Jerusalem (MG8: 1997), Rio de Janeiro (MG10: 2003), Berlin (MG11: 2006), Paris (MG12: 2009), Stockholm (MG13: 2012), and online (MG16: 2021).
The official opening ceremony of MG17 meeting took place on Monday morning, July 8, at the presence of Marco Marsilio, President of Abruzzo Region as well as of Carlo Masci, Mayor of Pescara. As every year, the MG17 Awards have been assigned during an official ceremony on July 9. This year, the Individual Awards went to:
The Institutional Awards went to CHIME/FRB Team, presented to Prof. Victoria Kaspi (McGill University, Canada) “for the innovative detection and comprehensive analysis of a large population of fast radio bursts, significantly increasing their statistics, including repeating sources, which have boosted our understanding of their origin and their application in mapping the universe structure and composition”.
The MG17 Awards booklet is available here: http://www.icra.it/mg/mg17/mg17_awards.pdf The five-day intense scientific program with plenary lectures in the morning held in the beautiful Aurum building and parallel sessions held in the afternoon both at Aurum and Ud’A in Pescara, lead to an intense exchange of new results, vivid discussions on the hottest topics including dark matter and dark energy, cosmological tensions, compact objects, astrophysical transients, gravitational waves and more traditional topics covered at MG meetings such as alternative theories of gravity, quantum gravity and experimental gravitation. The main discussions focused on the most recent observational results from the largest observatories, including James Webb Space Telescope, ground and underground facilities operating in multi-messenger domain such as neutrino and gravitational wave detectors. Particular attention was paid to the emerging field of artificial intelligence methods applied to analysis and interpretation of big data collected by both operative and not yet operative astrophysical observatories. All the abstracts submitted for the parallel sessions have been collected in the book of abstracts, available on the Indico platform for MG17 at the following link:https://indico.icranet.org/event/8/book-of-abstracts.pdf Three public lectures have been delivered in the evening sessions, namely by Prof. Wendy Freedman, Prof. Katherine Freese and Annapurni Subramanian.
The electronic proceedings of the 17th Marcel Grossmann meeting held on July 7-12, 2024 in Pescara, Italy, will be published by World Scientific. The editors will be Remo Ruffini and Gregory Vereshchagin. As previously done, the contributions from plenary speakers will be published in IJMPD. The proceedings submission has now started, so please consult the instruction for authors:https://indico.icranet.org/event/8/attachments/397/1170/instructions%20for%20authors.pdf The page limit is 20 pages and the deadline for submission is October 31, 2024.
The recordings of the different sessions (plenary and parallel session, official award ceremony, public lectures and round tables) are now available on the ICRANet YouTube channel at the following link:https://youtube.com/playlist?list=PLr5RLbSWSonsaGpKxkAiy3C_yRkhwfrpv&si=tsHSI_QCH_ryqrOF Several publishing companies were present along all the meeting in a space devoted to exhibitions, namely Cambridge University Press, Universe, World Scientific and Cambridge Scientific Publishers. Every session of the meeting has been broadcasted worldwide by the main TV, websites and press channels of China (https://www.icranet.org/documents/press_cinesi.pdf), Italy (https://www.icranet.org/documents/press_italiane.pdfand in other countries (https://www.icranet.org/documents/press_internazionali.pdf). Some news had an audience of over 100 million people in China and this confirmed once again the relevance of MG17 meeting in the field of Relativistic Astrophysics. Before the beginning of MG17 meeting, on Saturday July 6, the Municipality of Pescara has also held a press conference (https://www.ilpescara.it/attualita/meeting-marcel-grossman-7-12-luglio-presentazione-evento.html) The website of the meeting:https://indico.icranet.org/event/8/
4.The European Researchers' Night, September 27, 2024
As every year, ICRANet organized an event on the occasion of the European Researchers' Night, in order to create a nice occasion for discussion among citizens and researchers. This event attracted a lot of people, as every year, and offered 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.
The event was held at ICRANet center in Pescara and broadcasted online and has been attended by the students from 2 classes of Galileo Galilei High School in Pescara, under the supervision of their tutor, Prof. Tiziana Pompa (2019 Carlo Pace Prize winner). After the welcoming addresses by Prof. Ruffini, Director of ICRANet, he presented his talk titled “The most extreme gamma-ray burst ever observed, exploded on 25 August: GRB 240825A”. He spoke about his ongoing work on the GRB 240825A exploded on 25 August, which is located exactly on the borderline between short and long GRBs. Then, Prof. Yu Wang (ICRANet faculty Professor and President of ICRA), presented a talk titled “Artificial Intelligence in Astropysiscs”, showing the importance of using and training Artificial Intelligence in Astrophysics, and the great prospects in handling huge amounts of data. After him, Prof. Costantino Sigismondi, ICRANet Adjunct Professors, illustrated the achievement of the maximum solar brightness in the recent months. After the theoretical part, the students have been accompanied in ICRANet garden in order to observe the Sun with ICRANet telescope. The concluding remarks have been then presented by Prof. Ruffini, who thanked all the participants for joining this event.
Among the guests, Elisabetta Giannini, an architect at the Pescara Bar Association, and Laura Manfrini, from the L'Aquila Academy of Fine Arts, showing how important the alliance between science and art is.
At 8:30 PM, the meeting went on with a conference by Prof. Remo Ruffini “L’Universo dei Buchi Neri” in the framework of the event “Universo a km0”. This conference was held at Sala Incontri Valpolicella Benaco Banca in Valgatara (Italy). The conference of Prof. Ruffini in Valgatara:www.icranet.org/documents/talk_ruffini_valpolicella.mp4 The program of the event in Pescara:https://www.icranet.org/index.php?option=com_content&task=view&id=769
5.Upcoming meeting: the “3rd Julio Garavito Armero meeting”, November 13-15, 2024, Bucaramanga (Colombia)
We are happy to announce that ICRANet is organizing the 3rd Julio Garavito Armero meeting, which will be held from November 13 to 15, 2024 at the Universidad Industrial de Santander (UIS) in Bucaramanga (Colombia). This scientific meeting, co-organized by UIS, will follow a series of 2 successful conferences dedicated to Julio Garavito Armero, the Colombians most renowned astronomer, whose legacy has been honored by the International Astronomical Union by naming one of the Moon's craters after him. For the previous editions of the meeting:https://www.icranet.org/index.php?option=com_content&task=view&id=1355
The inauguration of the 3rd Julio Garavito Meeting will take place in Bogotá, at the Xavierian Pontifical University, on Tuesday, November 12, 2024. On that day, an opening ceremony will be held in the Carlos Corredor Auditorium of the Xavierian Pontifical University, followed by 45-minute talks. After lunch, two additional 45-minute talks will be offered. The lectures will be delivered by the event organizers.
This event reflects the ongoing commitment to scientific cooperation between ICRANet and Colombian universities and research centers. It will cover a wide range of topics related to relativistic astrophysics, astronomy, planetary science, cosmology, and solar physics. Key topics include compact stars (neutron stars, hybrid stars, quark stars, and white dwarfs), black holes, active galactic nuclei, and high-energy phenomena such as supernovae, hypernovae, gamma-ray bursts, and fast radio bursts. Additionally, gravitational lenses, gravitational waves, high-energy astroparticle physics, dark matter, cosmology, modified gravity models, and other related subjects will be explored.
In the mornings, plenary talks will be offered, while in the afternoons, spaces for interaction among students, professors, and researchers will be provided through poster sessions and workshops. The plenary talks will be presented in a hybrid format, allowing access via live streaming through Zoom and the ICRANet YouTube channel. Additionally, a public lecture will be held with the aim of strengthening our ties with the community.
The website of the meeting:https://jupyterhd.redclara.net/event/47/overview
6.Seminar by Prof. Ruffini “The first of the seven Episodes of BdHNe”, May 17, 2024, Princeton University (USA)
From May 16-18, 2024, Prof. Remo Ruffini, Director of ICRANet, visited the USA. During that visit, he has been invited by Prof. Lyman Page to deliver a seminar at Jadwin, in the Joe Henry room, at Princeton University (USA) on Friday, May 17, 2024 at 12 PM EST, titled “The first of the seven Episodes of BdHNe”. This Princeton University Gravity Group Lunch Seminar has been held in the framework of the Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium series.
Here below the abstract:
The multimessenger GRBs data and the theoretical considerations of neutron stars (NS) and black holes (BH) have identified in a binary system composed of a 10 solar mass CO core and a companion NS the progenitors of GRBs and their associated supernovae (SN). The collapse of the CO core leads to a SN, resulting in a newly born NS (vNS). The accretion of SN ejecta onto the NS binary companion results in the formation of a BH over periods ranging from minutes to hours, while accretion onto the vNS leads to the synchrotron emission observed in the afterglow. Using GRB 190114C as a prototype, we demonstrate the consistency of the observed optical emission of the GRB afterglow with the magnitudes expected from the naked-eye observations of the 1054 SN . We address the first 630 days of the SN as reported in historical Chinese, Korean an possibly European records. Additionally, extrapolating GRB data originating from the vNS and the BH over 970 years offers the possibility of explaining the spectral distribution of the CRAB observed today. Some general conclusions are inferred. We also examine the Penrose Process, the largely unexplored physics of the irreducible mass, and the role of electrodynamical process versus the gravitational ones. The video of the seminar:http://www.kaltura.com/tiny/e871e
7.Seminar by Prof. Gregory Vereshchagin and Prof. Mikalai Prakapenia “Pair creation in hot electrosphere of compact astrophysical objects”, February 8, 2024, ICRANet center in Pescara (Italy)
On Thursday, February 8, 2024, Prof. Gregory Vereshchagin (ICRANet Faculty) and Prof. Mikalai Prakapenia (ICRANet Minsk) presented a seminar titled “Pair creation in hot electrosphere of compact astrophysical objects” with the following abstract:
The mechanism of pair creation in electrosphere of compact astrophysical objects such as quark stars or neutron stars is revisited, paying attention to evaporation of electrons and acceleration of electrons and positrons, previously not addressed in the literature. We perform a series of numerical simulations using the Vlasov-Maxwell equations. The rate of pair creation strongly depends on electric field strength in the electrosphere. Despite Pauli blocking is explicitly taken into account, we find no exponential suppression of the pair creation rate at low temperatures. The luminosity in pairs increases with temperature and it may reach up to L±∼1052 erg/s, much larger than previously assumed. This seminar is based on their recent publication “Pair creation in hot electrosphere of compact astrophysical objects”, 2024 (https://arxiv.org/abs/2311.16653)
8.Seminar by Prof. Gregory Vereshchagin and Prof. Mikalai Prakapenia “Pair creation in hot electrosphere of compact astrophysical objects”, February 8, 2024, ICRANet center in Pescara (Italy)
From September 11 to 13, 2024, Prof. Remo Ruffini, Director of ICRANet, visited the ICRANet Seat in Nice at Villa Ratti. During that visit, he has been invited by the Musée des Beaux-Arts Jules Chéret of Nice to deliver a seminar on Thursday, September 12, 2024 at 4 PM, titled “Black Holes in the Universe”. This seminar is held in the framework of the exhibition “Berthe Morisot à Nice. Escales impressionnistes”, organized by the Museum in collaboration with ICRANet.
Here below the abstract: Les travaux développes à Princeton par John A. Wheeler et Remo Rufni en 1967 ont eu un éclat planétaire avec l'introducton conceptuelle du "Trou Noir" en astrophysique. Des intéressants anecdotes, qui se sont passés à la Vallée des Merveilles avec les Profs. Cécile Morette et Bryce DeWitt, seront mentionnés. Ensuite, la plus grande aventure scientifique jusqu'à aujourd’hui vient de se dérouler grâce à un numéro impressionnante d’observatoires dans l’espace ainsi que sur la surface terrestre, motivés par l’étude des Trous Noirs. Plusieurs Trous Noirs sont observés chaque jour dans tout l’Univers avec des masses de 10 à la 10 milliards de masses solaires. Parmi les plusieurs anecdotes, la préparation du Festschrift en l’honneur de Remo Ruffini à Villa Rat ainsi que les événements qui se sont déroules à Villa Rat par l’apposition des signatures par des éminents scientifiques et prix Nobel sur les murs de la Villa, seront présentés.
The announcement of the seminar on the Museum’s website:https://www.musee-beaux-arts-nice.org/agenda/conference-le-role-des-trous-noirs-dans-lunivers/
9. ICRANet participation at the conference “Black Holes & Cosmology” (BHCos 2024), March 11-15, 2024, Nassau (Bahamas)
On March 15, Prof. Ruffini (Director of ICRANet) and Prof. Jorge Rueda (ICRANet Faculty Professor and University of Ferrara), have been invited to present a lecture on the occasion of the conference “Black Holes & Cosmology” (BHCos 2024), held at the Nassau University in Bahamas and online, from March 11 to 15, 2024.
The purpose of this conference was to bring together world-renowned experts as well as junior researchers working on theoretical and observational aspects of black holes, particularly their role in cosmology. The topics discussed during the conference include Dark Matter, Structure Formation, Primordial Black Holes, Gravitational-Wave Astronomy and Quantum Aspects of Black Holes. Prof. Rueda presented a talk titled “The black hole of binary-driven hypernovae powering gamma-ray bursts”, while Prof. Ruffini presented a talk titled “On the Black Hole irreducible mass and the rotational energy extraction process”. Here below the abstract:
The Nature of long and Short extragalactic Gamma Ray Bursts (GRBs) and of their associated Supernovae has been addressed within the Binary Driven Hypernovae model (BDHN). Seven new episodes of ultrarelativistic regimes, previously unknown in terrestrial or galactic observations, have been found. They are observed with the largest ever multi messenger effort. New theoretical directions are followed to identify the rotational energy extraction process in Black Holes: reexamining new fundamental issues related to the Penrose Process, the largely unexplored physics of the irreducible mass, and the role of electrodynamical process versus the gravitational ones.
The website of the meeting:ttps://indico.mpp.mpg.de/event/9815/
10. ICRANet participation at the conference “Black Holes & Cosmology” (BHCos 2024), March 11-15, 2024, Nassau (Bahamas)
On Sunday March 17, 2024, Prof. Rremo Ruffini, Director of ICRANet, and Prof. Costantino Sigismondi, ICRANet Adjunct Professor, have been invited to present a lecture on the occasion of the “XXXIV Planetarium day 2024”, organized by the Nautical High School IIS Acciaiuoli – Einaudi of Ortona (Abruzzo, Italy). Prof. Ruffini gave an introductory lecture on the recent results achieved in Astrophysics, while Prof. Sigismondi presented a lecture titled “Galileo, Jupiter's Satellites and the longitude problem”.
After the conference, Prof. Ruffini and Prof. Sigismondi have also visited the School, the Planetarium as well as the nave scuola “San Tommaso” anchored at the port of Ortona.
The Planetarium in Ortona is dedicated to Prof. Antonio Malatesta, a former teacher of Navigation at the Ortona Nautical Institute. It was installed in 1964, has a 6-metre dome and can accommodate up to 45 people. Unique in Abruzzo, it attracts experts, scientists, students as well as astronomy enthusiasts.
Since 1991, the ‘Planetarium Day’ is organized in Italy on the Sunday before or after the spring equinox. The event takes place simultaneously in the main Italian planetaria. Since 1997, the ‘Planetarium Day’ has taken on an international character, also highlighted by a common logo adopted by the planetariums participating in the event.
Video of the conference: https://www.facebook.com/watch/?v=327138740342466
11. ICRANet participation at the “35th Tehran International Book Fair” (TIBF), May 8-18, 2024
From November 3 to 5, 2021, ICRANet organized the “ICRANet - Isfahan Astronomy Meeting. From the Ancient Persian Astronomy to Recent Developments in Theoretical and Experimental Physics, Astrophysics and General Relativity”, the first ICRANet international meeting in Iran held at the Isfahan University of Technology (IUT) and online. The opening remarks of this meeting have been presented by H.E. Mohammad Ali Zolfigol, then Minister of Science, Research and Technology of the Islamic Republic of Iran. The proceedings of this meeting have been already published in the Eurasian Astronomical Society - Astronomical and Astrophysical Transactions, Volume 33, issue 3 on December 2022 by Cambridge Scientific Publishers. The book edition of these proceedings has recently been published by Cambridge Scientific Publishers.
The volume “ICRANet-Isfahan Astronomy meeting: from ancient Persian astronomy to recent developments in theoretical and experimental Physics, Astrophysics and General Relativity”, published by Cambridge Scientific Publisher, has been presented in an official ceremony on the occasion of the 35th Tehran International Book Fair (TIBF), which is taking from May 8 to 18, 2024, with an online presentation by Prof. Remo Ruffini, Prof. Soroush Shakeri (Isfahan University of Technology) and Janie Wardle (President Cambridge University Publisher).
The Tehran International Book Fair is staged in Tehran in May on an annual basis. The first edition of the international cultural event was held in 1988 with 16 thousands titles of book on show. The cultural event has turned into a landmark, momentous book fair in the Middle East and Asia after 34 editions in a row. Millions of visitors visit the fair every year, including thousands of university students, scholars and their families. The event is one of the most significant cultural events in Iran.
The website of the Fair: https://tibf.ir/en
12. ICRANet participation at the “45th COSPAR Scientific Assembly”, July 13-21, 2024, Busan (South Korea)
On July 17, 2024, Prof. Ruffini (Director of ICRANet) has been invited to present a lecture on the occasion of the “45th COSPAR Scientific Assembly”, held in Busan (South Korea) from July 13 to 21, 2024. Launched in 1958, the annual COSPAR scientific assemblies have changed its format to a biennial gathering from 1980 and assemblies held in even-numbered years for the past four decades have been recognized as a renowned academic agora for space research scientists and pertinent partakers.
On that occasion, Prof. Ruffini presented a talk titled “On the Black Hole (BH) irreducible mass (Mirr) and the rotational energy extraction process”. Here below the abstract: The issue of the rotational energy extraction from BHs as the energy source of stellar mass BHs in Gamma-Ray Bursts (GRBs) and in BHs of 1010 stellar mass in AGNs is here analyzed in connection with the contribution of Rueda et al. and Bulanov et al. in this session. The fundamental BH formula by Christodoulou [1], Christodoulou and Ruffini [2], and S. Hawking [3] relates the BH mass-energy formula M to 3 parameters: 1) the angular momentum L, 2) the charge Q, and 3) the irreducible mass Mirr. The Mirr is related to the BH surface area S, monotonically increasing, by S = 16M2 irr. We first recall the BH properties as classic systems for mass larger than the Planck Mass. We review the three-particle ballistic process of Penrose extracting energy of an isolated Kerr BH in vacuum and recall as well the manyparticle generalizations. The constraints imposed on a pure gravitational extraction process are specifically evidenced. We then turn to the Kerr-Newman (KN) solutions and show how the energy source of GRBs, originating BHs, NSs, and SNs, as well as AGNs can be justified by relaxing the BH vacuum condition and the asymptotically flat solution by generalizing a Wald-Papapetrou solution in presence of plasma. We finally show how the irreducible mass is the classical alternative to the BH entropy. The website of the meeting: https://cospar2024.org/
13. ICRANet participation at the “XXIV Gamow International Astronomical Conference”, August 19-23, 2024, Odesa (Ukraine)
On Tuesday August 20, 2024, Prof. Ruffini (Director of ICRANet) has been invited to present a plenary ecture on the occasion of the “XXIV Gamow International Astronomical Conference”, held online in Odesa (Ukraine) from August 19 to 23, 2024. The 2024 conference marks the 120th anniversary of the birth of George Gamow, one of the active participants in the revolution in physics and astrophysics of the 20th century. It also marks 30 years since the commencement of the Gamow Conferences in Odesa, the city where Gamow was born and raised, and where he chose his scientific career.
The conference highlighted contemporary trends in the development of cosmology and astrophysics, especially in the areas in which Gamow actively contributed.
On that occasion, Prof. Ruffini presented a talk titled “The role of Fermi in the discussion of Gamow cosmology: an international implication”. Here below the abstract: We recall the work of Fermi in completing the cosmological nucleosynthesis and evidencing first the role of formation of the light element in cosmology, opening a new era in Relativistic Astrophysics of the Big Bang. The website of the meeting: https://gamow.odessa.ua/
14. ICRANet press release “Aurora predicted for the dawn of Saturday 11 may also in Italy”, May 11, 2024
The solar flares are very energetic phenomena, the two observed on may 10, 2024 reached the 10^28 erg/s in the -ray band (X4- class).
The ICRANet expert in Solar Physics, Costantino Sigismondi, organized promptly an event to observe the to flares in white light, as the Carrington event in 1859 from 6:30 to 7:40 UT on Friday May 10, and he will present the results at the Lyceum Galileo Galilei of Pescara monday 13 May. Meanwhile NASA annouced a strong geomagnetic storm for the early hours of Saturday 11 May, and the observations of the sky toward North-North East are recommended from 4 AM local time for all European sites, also Italy. A reddish aurora, due to the ionization of the upper atmosphere made by the protons coming from the Coronal Mass Ejections sent toward our planet on Thursday May 9, may be visible from our middle latitudes skyes. "Not easy to be recognized from the artificial light pollution", says Costantino Sigismondi, who observed it on the late evening of 31st October 2003 from Lanciano, countryside, "but it is worth to wake up for a lifetime astronomical event!". It is a very high energy event occurred so close to the Earth, still very small with respect to the powerful GRB, but able to send some gamma rays toward our planet, thanks to the magnetic reconnection which releases a strong amount of energy in a few minutes of duration. ICRANet has organized some observations in order to study the phenomenon, as well as a lecture to the students of the High School Galileo Galilei in Pescara. The event, curated by ICRANet solar astrophysicist Costantino Sigismondi, involves ERASMUS
secondary school and university students:
https://icranet.org/index.php?option=com_content&task=view&id=1534 https://youtu.be/Cq64LBIgnFw The press release on ICRANet website:https://icranet.org/communication/100524/press_release_Flare_en.pdf
15. ICRANet press release “Aurora predicted for the dawn of Saturday 11 may also in Italy”, May 11, 2024
On September 16, 2024, Prof. Remo Ruffini, Director of ICRANet, had an institutional visit to the President of the Abruzzo Region, Dr Marco Marsilio in the Regione Abruzzo building in L’Aquila (Italy). The institutional meeting has been also attended by Dr Roberto Santangelo (regional Assessor in charge of universities and research), Prof. Massimo Della Valle (Chairman ICRANet Scientific Committee, member of the board of directors of INAF), and Prof. Yu Wang (ICRANet Faculty Professor and President of ICRA).
This meeting followed the 17th Marcel Grossman Meeting, organized by ICRANet in Pescara last July, which brought together more than 700 scientists from 52 countries. During this institutional meeting, the central role that Abruzzo Region plays among scientists in the fields of research and the studies of the Universe was reaffirmed. All these ongoing collaborations involve the national nuclear physics laboratories under the Gran Sasso, research at the Gran Sasso Science Institute (GSSI) and the Collurania astronomical observatory in Teramo and will enable further studies to be launched with the support and the collaboration of Abruzzo Region.
Here below, some press releases (in Italian) appeared on this institutional meeting:
16. ICRANet participation at the Chinese Embassy reception, September 17, 2024
On September 17, 2024, Prof. Remo Ruffini (Director of ICRANet), Prof. Massimo Della Valle (Chairman ICRANet Scientific Committee, member of the board of directors of INAF) as well as Prof. Yu Wang (ICRANet Faculty Professor and President of ICRA), have been invited to attend a reception the occasion of the 75th Anniversary of the Foundation of the People’s Republic of China as well as of the 20th Anniversary of the China-Italy Global Strategic Partnership. The reception, organized by the Chinese Ambassador to Italy, H.E. Jia Guide, has been held at the Hotel Cavalieri Waldorf Astoria in Rome and has been also attended by many eminent Italian political personalities.
On behalf of the Chinese Embassy in Italy, Ambassador Guide expressed his gratitude to all the participants, who had long cherished China's development and supported Sino-Italian friendship. He highlighted how, in seventy-five years of commitment and progress, China has experienced epochal changes, explored and succeeded in embarking on a path of development suited to China's national conditions, achieving world-renowned development achievements and bringing opportunities to the world.
In 20 years, the global strategic partnership between China and Italy gave fruitful results: mutual political trust has been steadily strengthened, mutually beneficial cooperation has been developed vigorously and also multilateral cooperation has been further promoted.
17. ICRANet participation at the Armenian Embassy reception, Semptember 25, 2024
On September 25, 2024, Prof. Remo Ruffini (Director of ICRANet) and Prof. Yu Wang (ICRANet Faculty Professor and President of ICRA), have been invited to attend a reception in Rome on the occasion of the Armenian National Day - the 33rd anniversary of the independence of the Republic of Armenia. The reception has been organized by the Armenian Embassy in Rome, also on the occasion of the conclusion of the mission to the Ambassador, H.E. Ms Tsovinar Hambardzumyan. The reception has been attended, among others, by the Italian Deputy Prime Minister, Minister of Transport and Infrastructure Matteo Salvini. Also present were Undersecretary of State for Foreign Affairs and International Cooperation Giorgio Silli, Deputy Minister of Justice Francesco Paolo Sisto and Undersecretary of State Andrea Delmastro Delle Vedova, First President of the Court of Cassation Margherita Cassano, President of the Court of Appeal Giuseppe Meliado, Military Attorney General Maurizio Block, and President of the Italy-Armenia Friendship Group Giulio Centemero, deputies and senators representing all the political forces in the Italian Parliament, chairmen of commissions, Italian government officials and the Presidency, Ambassadors accredited to Italy, diplomats, representatives of the academic, cultural, journalistic, health and educational sectors, honorary consuls of the Republic of Armenia in Milan, Venice and Bari, and representatives of the Armenian community.
18. Prof. Ruffini among the top 2% of the most cited authors, according to Elsevier
Recent update of the publicly available database of over 100,000 top-scientists listed by Elsevier, show that Prof. Remo Ruffini (Director of ICRANet), Prof. Behzad Eslam Panah (ICRANet-Mazandaran, Iran) and several other ICRANet scientists are in this list.
Elsevier has created this publicly available database of top-cited scientists, which provides standardized information on citations, h-index, co-authorship adjusted hm-index and citations to papers in different authorship positions. Scientists are classified into 22 scientific fields and 174 sub-fields, which are also provided for all scientists with at least 5 papers. Career-long data are updated to the end of 2021 and single recent year data pertain to citations received during 2021. T The selection is based on the top 100,000 scientists by c-score (with and without self-citations) or a percentile rank of 2% or above in the sub-field. This version (7) is based on the August 1, 2024 snapshot from Scopus, updated to end of citation year 2023. This work uses Scopus data. Calculations were performed using all Scopus author profiles as of August 1, 2024. to consult the complete list: https://elsevier.digitalcommonsdata.com/datasets/btchxktzyw/7
19. Publication of the 5th Zeldovich meeting proceedings, February 25, 2024
It is our great pleasure to inform you that the proceedings of the 5th Zeldovich meeting, held in Yerevan (Armenia) from June 12 to 16, 2024 have been published on February 25, 2024 in a special issue of Astronomy Reports (Astronomy Reports, Volume 67, Issue 2 supplement) as open access document:https://link.springer.com/journal/11444/volumes-and-issues/67-2/supplement
These proceedings include 200 papers resulting in 218 pages of printed volumes covering virtually all topics discussed during the meeting, such as multimessenger astrophysics, early universe, large scale structure, cosmic microwave background, neutron stars, black holes, gamma-ray bursts, supernovae, hypernovae, gravitational waves, quantum and gravity. We recall that this meeting also commemorated the 80th anniversary of the National Academy of Sciences of the Republic of Armenia, whose members gave equally fundamental contributions to the field of Relativistic Astrophysics. The editors of these proceedings are Gregory Vereshchagin, Remo Ruffini and Narek Sahakyan.
20. Publication of the 5th Zeldovich meeting proceedings, February 25, 2024
It is our great pleasure to inform you that the special issue “Remo Ruffini Festschrift” has been published on June 2024 in a special issue by MDPI, Universe, also as open access document:https://www.mdpi.com/journal/universe/special_issues/J0M337731D
A conference celebrating Remo Ruffini's 80th birthday was held in Nice, France, from 16 to 18 May 2022, with the participation of over 90 scientists. Among the contributions presented orally there were those by Rashid Sunyaev, Peter Predehl, Demetrios Christodoulou, Thibault Damour, Nathalie Deruelle, Roy Kerr, Tsvi Piran, Claus Laemmerzahl, Asghar Qadir, Chen Pisin, and Marco Tavani, in the presence of Agnès Rampal, the representative of the Mayor of Nice. An extraordinary moment of the meeting in Nice was the delivery of the Marcel Grossmann Award to Rashid Sunyaev and Peter Predehl for the Spectr–Roentgen–Gamma (SRG) mission. This special issue volume collects 10 papers written by distinguished scholars, meeting participants and collaborators, dedicated to Prof. Remo Ruffini on the occasion of his 80th birthday.
The editors of this special issue are Remo Ruffini, Jorge Armando Rueda Hernández, Narek Sahakyan and Gregory Vereshchagin.
21. Publication of the article “From “introducing the black hole” (1971) to the discoveries of an alive black hole in GRB 190114C (2021) a collection of documents prepared in occasion of the 17th Italo-Korean meeting”, September 6, 2024
It is our pleasure to inform you that the article “From “introducing the black hole” (1971) to the discoveries of an alive black hole in GRB 190114C (2021) a collection of documents prepared in occasion of the 17th Italo-Korean meeting” has been published on September 6, 2024 by AIP Publishing(Volume 2874, Issue 1).
This contribution by Prof. Remo Ruffini (https://doi.org/10.1063/5.0216360)is part of the conference proceedings of the 17th Italo-Korean meeting (IK17), co-organized by ICRANet, held from August 2 to 6, 2021 online and at Kunsan National University in South Korea: https://pubs.aip.org/aip/acp/issue/2874/1
The editors of this proceedings are Stefano Scopel, Remo Ruffini, Bum-Hoon Lee, Sangpyo Kim, Hyung Won Lee, Bogeun Gwak and Wonwon Lee.
22. Three conferences on the 2024 leap year “Julius Caesar's algorithm and Gregory XIII’s algorithm”, February 2024
Three conferences on the 2024 leap year have been organized by Prof. Costantino Sigismondi, ICRANet Adjunct Professor, on February 24 at Lanciano- Antoniano, on February 26 - 27 at ICRANet Hq as well as at the High School Galileo Galilei in Pescara, and on February 29 in Rome, at the Cathedral S. Maria degli Angeli e dei Martiri. The main objective of these meeting has been to understand better what is behind these two civil calendar reforms valid for the whole world, both prepared in Rome: the Julius Caesar's algorithm and Gregory XIII’s algorithm.
In 46 BC, the Roman Senate, upon request of Pontifex Maximus, modified the ancient Calendar of Numa Pompilius introducing the bi-sixth day of the Kalends of March once every four years: it was February 24. On the same date in 1582, with the papal bull “Inter Gravissimas” of Gregory XIII P.M., he corrected the Julian algorithm, removing three leap years on four. In both reforms, the days of difference accumulated in the previous centuries concerning astronomy, have been eliminated. Behind Julius Caesar there was the Egypt of the Ptolemies, and the Roman Calendar that was essentially lunar (ides, none and kalends) and behind Gregory XIII there was Easter, which was moving from Spring to Summer and also the Full Moon to be calculated, in the future centuries, in a clear, univocal and possibly simple way.
In the historical presentation on the occasion of these 3 conferences, prof. Sigismondi addressed also the logical-mathematical aspect of the two algorithms and of their observational verification, which for the Gregorian reform, implied for over a century and a half the activity of the Calendar Commission, lastly chaired by Francesco Bianchini (1662-1729), the author of the Clementine Sundial at S. Maria degli Angeli e dei Martiri (1702), in order to obtain the observations supporting the Gregorian algorithm.
Tomb of Gregory XIII, created by Camillo Rusconi in 1623: https://youtu.be/cLkvZHd9ngE
Algorithms from Julius Caesar to Gregory XIII:https://youtu.be/Gz5hUhwqYvQ From the notes of Galileo:https://youtu.be/tUipCo4dRtg Pollen crowns around the Sun “identification and study”: https://youtu.be/62rXZp6VZns
The webpage of the conferences:https://www.icranet.org/index.php?option=com_content&task=view&id=1528
23. “Total eclipse at Solar Maximum”, observations and conference, April 6-8, 2024
The eclipse season peaks now with the Great American Eclipse, involving millions of people into this experience, which is ancestral as well as scientific. Saint Luke in his gospel (Lc 23, 45) described the good Friday’s obscurity at the Jesus' death on the cross with such an eclipse, probably experienced by himself in 29 AD in Antioch, his city of origin. Angelo Secchi observed the eclipse of 1860 near the solar maximum, and he was coordinated with Warren de la Rue to photograph this eclipse to measure the parallax of the solar corona and prominences in order to verify that it was not lunar. Since 1999, we study eclipses as method to measure accurately the solar diameter, following the Rome Observatory research started in XIX century, in connection with the IAU Solar Eclipses Working Group, once directed by Jay Pasachoff (1943-2022), who participated to the previous editions of this meeting. This eclipse gives to us the occasion to gather new data and discuss old ones, to discover the many aspects of solar variability and put them in correlation with our climate change.
Experts of this field participated to this event, and the main topics addressed were climate change: the observables, secular solar diameter variations and solar corona at solar maximum. For the video of the conference:https://youtu.be/TYYBcJTGczY
The sizigial equinoctial tides are the largest in the year (Newton, Principia, 1687) and with the solar eclipse ongoing we have the occasion to see its gravitational effects on the sea level, whose signal is normally disturbed by meteorological seiches. Oceanographical observations made in Ortona (Nautical Institute), Pescara and Ostia parallel the astronomical event.
The webpage of the meeting:https://www.icranet.org/index.php?option=com_content&task=view&id=1531
24. “2024 Gerbertus’ day: X-ray solar flares, Coronal Mass Ejections and Aurorae”, May 11-12, 2024
After a series of CME and X-rays solar flares of X-class a reliable auroral display is being predicted by the NASA models before dawn on Saturday 11 May and Sunday 12 May 2024. The great AR 3664 sunspots system has been observed worldwide, even at the meridian line of st. Maria degli Angeli in Rome on May 9, because it spans more than 20% of the solar diameter.
Here the videos of such peculiar event (the first time in 25 years) recorded during an ERASMUS visit at the Basilica:
The webpage of the meeting:https://www.icranet.org/index.php?option=com_content&task=view&id=1534
25. New “Convention de partenariat” between ICRANet and the Municipality of Nice”, April 22, 2024
On 22 April, 2024 ICRANet signed a partnership agreement with the Municipality of Nice, for its Jules Chéret Fine Arts Museum.
The main purpose of this agreement is the joint organization of activities, events of a cultural nature, aimed at the widest possible audience, by the Musée des Beaux-Arts Jules Chéret de Nice and ICRANet, in collaboration, at the ICRANet Seat in Villa Ratti (Nice) and the Musée des Beaux-Arts Jules Chéret. This will be done in compliance with current safety regulations: guided tours and special workshops, conferences, symposia, round-table discussions and study days. This convention was signed by the Mayor of Nice, Christian Estrosi, and by Prof. Ruffini, Director of ICRANet.
26. Renewal of the cooperation protocol between ICRANet and the Al-Farabi Kazakh National University (KAZNU), May 2, 2024
On May 2, 2024, the Cooperation Agreement between ICRANet and the Al-Farabi Kazakh National University (KAZNU) has been renewed. The renewal was signed by Aitzhanova Zhamila (Meeber of the Board of Vice-Rector for Research and Invnnovation of KAZNU), Prof. Abishev Medeu (KAZNU), Prof. Remo Ruffini (Director of ICRANet) and Prof. Jorge Rueda (ICRANet Faculty Professor).
This agreement will be valid for 5 additional years and the main joint activities to be developed under its framework include: the conduction of joint research on scientific issues of interest to both parties, the organization of bilateral scientific and scientific-practical events, the exchange of experience between employees involved in research and teaching, the publication of joint scientific works in international journals as well as the exchange of publications, teaching materials and lecture courses. The text of the agreement:http://www.icranet.org/icranet-kazakhstan
27. New cooperation protocol between ICRANet and the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A), July 19, 2024
On July 19, 2024 ICRANet has signed a new Cooperation protocol with the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A) in Abruzzo (Italy). The Cooperation Protocol has been signed by Prof. Liborio Stuppia (Rector of Ud’A), Prof. Piero Di Carlo (Ud’A), Prof. Remo Ruffini (Director of ICRANet) and Prof. Jorge A. Rueda h. (ICRANet Faculty Professor).
The agreement will be valid for 5 years and the main joint activities to be developed under their framework include: the institutional exchange of graduate, post-graduate students, researchers and faculty members, the development of teaching and/or research activities related to the areas of expertise and interest of both the organizations, the organization of symposia, seminars, conferences and short courses, the promotion and support of technical-scientific and cultural events and activities open to the public; the development of opportunities to form university teachers and researchers, the organization of training and recycling courses and activities as well as the developing of inter-institutional research areas associated to local graduate programs; the promotion of joint publications; the implementation of socially oriented activities through the academic extension; the exchange of information concerning teaching and research activities in both institutions as well as the applications to the international grant programs to promote joint research projects or implement mobility exchange programs.
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1535
28. Prof. Ruffini awarded the prize “Federico Valignani”, August 9, 2024, Torrevecchia Teatina (Italy)
On August 9, 2024, Prof. Remo Ruffini, Director of ICRANet, was awarded the prize “Federico Valignani”, on the occasion the first edition of this prize within the XXIV edition of the Festival Lettera d’Amore, sponsored by the Municipality of Torrevecchia Teatina (Italy), the Museum Lettera d’Amore and the Abruzzo Region.
This award has been assigned by the scientific committee to Prof. Ruffini “for having conceived science as a value, and, having achieved very high results, for the great merit of continuing his magisterium by evaluating and educating the best young students from all over the world in the field of research”.
29. Joint Call for Proposals “BRFFR - ICRANet 2025”
On April 26, 2024, the Belarusian Republican Foundation for Fundamental Research (BRFFR) and ICRANet announced a call for proposals for joint basic research projects in relativistic astrophysics. The scientific areas covered by the call are Relativistic astrophysics, Cosmology and Gravitation.
Joint applications from international research teams including Belarusian scientists must be submitted simultaneously using agreed application forms to both organizations: Belarusian team apply to the BRFFR, international ones - to ICRANet. The duration of the projects is up to 2 years and the deadline for applications November 5, 2024. For more information about the call and to download the application form, please use the link:https://www.icranet.org/index.php?option=com_content&task=view&id=1447
30. Visit of Librorio Stuppia, Rector of the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A), at the ICRANet center in Pescara, March 25, 2024”
On March 25, 2024, Prof. Liborio Stuppia, Rector of the University Gabriele D’Annunzio of Chieti-Pescara (Ud’A), visited the ICRANet center in Pescara, together with Prof. Angelo Cichelli, Director of Scuola Superiore Ud’A and Prof. Piero Di Carlo from Ud’A.
During their visit, they met Professor Remo Ruffini, Director of ICRANet. He accompanied them in a comprehensive tour of the center, showing her ICRANet library and explaining her all the important achievements and current researches carried on by the center. The Rector also met the ICRANet staff, Faculty and students, who told her about their important work and experience here in Pescara.
31. Scientific visits to ICRANet
During their visit, those scientists had an opportunity to discuss their scientific research and to have fruitful exchange of ideas with other researchers from ICRANet and from different parts of the world.
32. Recent publications
N. Sahakyan, D. Bégué, A. Casotto, H. Dereli-Bégué, P. Giommi, S. Gasparyan, V. Vardanyan, M. Khachatryan, and A. Pe'er, Modeling Blazar Broadband Emission with Convolutional Neural Networks. II. External Compton Model, published on The Astrophysical Journal, Volume 971, Issue 1, on August 6, 2024.
In the context of modeling spectral energy distributions (SEDs) for blazars, we extend the method that uses a convolutional neural network (CNN) to include external inverse Compton processes. The model assumes that relativistic electrons within the emitting region can interact with and up-scatter external photons originating from the accretion disk, the broad-line region, and the torus, to produce the observed high-energy emission. We trained the CNN on a numerical model that accounts for the injection of electrons, their self-consistent cooling, and pair creation-annihilation processes, considering both internal and all external photon fields. Despite the larger number of parameters compared to the synchrotron self-Compton model and the greater diversity in spectral shapes, the CNN enables an accurate computation of the SED for a specified set of parameters. The performance of the CNN is demonstrated by fitting the SED of two flat-spectrum radio quasars, namely 3C 454.3 and CTA 102, and obtaining their parameter posterior distributions. For the first source, the available data in the low-energy band allowed us to constrain the minimum Lorentz factor of the electrons, ϓmin, while for the second source, due to the lack of these data, ϓmin = 102 was set. We used the obtained parameters to investigate the energetics of the system. The model developed here, along with one from Bégué et al., enables self-consistent, in-depth modeling of blazar broadband emissions within a leptonic scenario.
D. Bégué, N. Sahakyan, H. Dereli-Bégué, P. Giommi, S. Gasparyan, M. Khachatryan, A. Casotto, and A. Pe'er, Modeling Blazar Broadband Emission with a Convolutional Neural Network. I. Synchrotron Self-Compton Model, published on The Astrophysical Journal, Volume 963, Issue 1 on February 29, 2024.
Modeling the multiwavelength spectral energy distributions (SEDs) of blazars provides key insights into the underlying physical processes responsible for the emission. While SED modeling with self-consistent models is computationally demanding, it is essential for a comprehensive understanding of these astrophysical objects. We introduce a novel, efficient method for modeling the SEDs of blazars by the mean of a convolutional neural network (CNN). In this paper, we trained the CNN on a leptonic model that incorporates synchrotron and inverse Compton emissions, as well as self-consistent electron cooling and pair creation–annihilation processes. The CNN is capable of reproducing the radiative signatures of blazars with high accuracy. This approach significantly reduces the computational time, thereby enabling real-time fitting to multiwavelength data sets. As a demonstration, we used the trained CNN with MultiNest to fit the broadband SEDs of Mrk 421 and 1ES 1959+650, successfully obtaining their parameter posterior distributions. This novel framework for fitting the SEDs of blazars will be further extended to incorporate more sophisticated models based on external Compton and hadronic scenarios, allowing for multimessenger constraints in the analysis. The models will be made publicly available via a web interface at the Markarian Multiwavelength Data Center to facilitate self-consistent modeling of multimessenger data from blazar observations.
N Sahakyan, G Harutyunyan, S Gasparyan, D Israyelyan, Broad-band study of gamma-ray blazars at redshifts z = 2.0-2.5, published in Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 4 on January 31, 2024.
High redshift blazars are among the most powerful non-explosive sources in the Universe and play a crucial role in understanding the evolution of relativistic jets. To understand these bright objects, we performed a detailed investigation of the multiwavelength properties of 79 γ-ray blazars with redshifts ranging from z = 2.0 to 2.5, using data from Fermi LAT, Swift XRT/UVOT, and NuSTAR observations. In the γ-ray band, the spectral analysis revealed a wide range of flux and photon indices, from 5.32 × 10−10 to 3.40 × 10−7 photon cm−2 s−1 and from 1.66 to 3.15, respectively, highlighting the diverse nature of these sources. The detailed temporal analysis showed that flaring activities were observed in 31 sources. Sources such as 4C+71.07, PKS 1329-049, and 4C + 01.02, demonstrated significant increase in the γ-ray luminosity and flux variations, reaching peak luminosity exceeding 1050 erg s−1. The temporal analysis extended to X-ray and optical/ultraviolet (UV) bands, showed clear flux changes in some sources in different observations. The time-averaged properties of high redshift blazars were derived through modeling the spectral energy distributions with a one-zone leptonic scenario, assuming the emission region is within the broad-line region (BLR) and the X-ray and γ-ray emissions are due to inverse Compton scattering of synchrotron and BLR-reflected photons. This modeling allowed us to constrain the emitting particle distribution, estimate the magnetic field inside the jet, and evaluate the jet luminosity, which is discussed in comparison with the disc luminosity derived from fitting the excess in the UV band.
P. Giommi1,2,3, N. Sahakyan4,5, D. Israyelyan4, and M. Manvelyan4, The Remarkable Predictive Power of Infrared Data of Blazars, published in The Astrophysical Journal, Volume 963, Issue 1 on February 28, 2024.
Blazars are the brightest and most abundant persistent sources in the extragalactic γ-ray sky. Due to their significance, they are often observed across various energy bands, where the data of which can be used to explore potential correlations between emission at different energies, yielding valuable insights into the emission processes of their powerful jets. In this study we utilized IR data at 3.4 and 4.6 μm from the Near-Earth Object Wide-field Infrared Survey Explorer Reactivation Mission, spanning 8 yr of observations, X-ray data from the Neil Gehrels Swift Observatory collected throughout the satellite's lifetime, and 12 years of γ-ray measurements from the Fermi Large Area Telescope's all-sky survey. Our analysis reveals that the IR spectral slope reliably predicts the peak frequency and maximum intensity of the synchrotron component of blazar spectral energy distributions, provided it is uncontaminated by radiation unrelated to the jet. A notable correlation between the IR and γ-ray fluxes was observed, with the BL Lacertae subclass of blazars displaying a strong correlation coefficient of r = 0.80. IR band variability is more pronounced in flat spectrum radio quasars than in BL Lacertae objects, with mean fractional variability values of 0.65 and 0.35, respectively. We also observed that the synchrotron peak intensity of intermediate-high-energy-peaked objects can forecast their detectability at very high γ-ray energies. We used this predicting power to identify objects in current catalogs that could meet the detection threshold of the Cerenkov Telescope Array extragalactic survey, which should encompass approximately 180 blazars.
Dhurba Tripathi, Paolo Giommi, Adriano Di Giovanni, Rawdha R. Almansoori, Nouf Al Hamly, Francesco Arneodo, Andrea V. Macciò, Goffredo Puccetti, Ulisses Barres de Almeida, Carlos Brandt, Simonetta Di Pippo, Michele Doro, Davit Israyelyan, A. M. T. Pollock, and Narek Sahakyan, Firmamento: A Multimessenger Astronomy Tool for Citizen and Professional Scientists, published in The Astronomical Journal, Volume 167, Issue 3 on February 19, 2024.
Firmamento (https://firmamento.hosting.nyu.edu is a new-concept, web-based, and mobile-friendly data analysis tool dedicated to multifrequency/multimessenger emitters, as exemplified by blazars. Although initially intended to support a citizen researcher project at New York University–Abu Dhabi, Firmamento has evolved to be a valuable tool for professional researchers due to its broad accessibility to classical and contemporary multifrequency open data sets. From this perspective Firmamento facilitates the identification of new blazars and other multifrequency emitters in the localization uncertainty regions of sources detected by current and planned observatories such as Fermi-LAT, Swift, eROSITA, CTA, ASTRI Mini-Array, LHAASO, IceCube, KM3Net, SWGO, etc. The multiepoch and multiwavelength data that Firmamento retrieves from over 90 remote and local catalogs and databases can be used to characterize the spectral energy distribution and the variability properties of cosmic sources as well as to constrain physical models. Firmamento distinguishes itself from other online platforms due to its high specialization, the use of machine learning and other methodologies to characterize the data, and for its commitment to inclusivity. From this particular perspective, its objective is to assist both researchers and citizens interested in science, strengthening a trend that is bound to gain momentum in the coming years as data retrieval facilities improve in power and machine-learning/artificial-intelligence tools become more widely available.
MAGIC collaboration, Constraints on Lorentz invariance violation from the extraordinary Mrk 421 flare of 2014 using a novel analysis method, published in Journal of Cosmology and Astroparticle Physics, Volume 2024, Issue 07 on July 19, 2024.
The Lorentz Invariance Violation (LIV), a proposed consequence of certain quantum gravity (QG) scenarios, could instigate an energy-dependent group velocity for ultra-relativistic particles. This energy dependence, although suppressed by the massive QG energy scale E_QG, expected to be on the level of the Planck energy 1.22 × 1019 GeV, is potentially detectable in astrophysical observations. In this scenario, the cosmological distances traversed by photons act as an amplifier for this effect. By leveraging the observation of a remarkable flare from the blazar Mrk 421, recorded at energies above 100 GeV by the MAGIC telescopes on the night of April 25 to 26, 2014, we look for time delays scaling linearly and quadratically with the photon energies. Using for the first time in LIV studies a binned-likelihood approach we set constraints on the QG energy scale. For the linear scenario, we set 95% lower limits E_QG>2.7×1017 GeV for the subluminal case and E_QG> 3.6 ×1017 GeV for the superluminal case. For the quadratic scenario, the 95% lower limits for the subluminal and superluminal cases are E_QG>2.6 ×1010 GeV and E_QG>2.5×1010 GeV, respectively.
MAGIC collaboration, Constraints on axion-like particles with the Perseus Galaxy Cluster with MAGIC, published in Physics of the Dark Universe, Volume 44 on May 2024.
Axion-like particles (ALPs) are pseudo-Nambu–Goldstone bosons that emerge in various theories beyond the standard model. These particles can interact with high-energy photons in external magnetic fields, influencing the observed gamma-ray spectrum. This study analyzes 41.3 h of observational data from the Perseus Galaxy Cluster collected with the MAGIC telescopes. We focused on the spectra the radio galaxy in the center of the cluster: NGC 1275. By modeling the magnetic field surrounding this target, we searched for spectral indications of ALP presence. Despite finding no statistical evidence of ALP signatures, we were able to exclude ALP models in the sub-micro electronvolt range. Our analysis improved upon previous work by calculating the full likelihood and statistical coverage for all considered models across the parameter space. Consequently, we achieved the most stringent limits to date for ALP masses around 50 neV, with cross sections down to gαγ = 3x 1012 GeV−1.
MAGIC collaboration, Insights into the broadband emission of the TeV blazar Mrk 501 during the first X-ray polarization measurements, published in Astronomy & Astrophysics, Volume 685 on May 22, 2024.
Aims. We present the first multiwavelength study of Mrk 501 that contains simultaneous very-high-energy (VHE) γ-ray observations and X-ray polarization measurements from the Imaging X-ray Polarimetry Explorer (IXPE).
Methods. We used radio-to-VHE data from a multiwavelength campaign carried out between March 1, 2022, and July 19, 2022 (MJD 59639 to MJD 59779). The observations were performed by MAGIC, Fermi-LAT, NuSTAR, Swift (XRT and UVOT), and several other instruments that cover the optical and radio bands to complement the IXPE pointings. We characterized the dynamics of the broadband emission around the X-ray polarization measurements through its multiband fractional variability and correlations, and compared changes observed in the polarization degree to changes seen in the broadband emission using a multi-zone leptonic scenario.
Results. During the IXPE pointings, the VHE state is close to the average behavior, with a 0.2–1 TeV flux of 20%–50% of the emission of the Crab Nebula. Additionally, it shows low variability and a hint of correlation between VHE γ-rays and X-rays. Despite the average VHE activity, an extreme X-ray behavior is measured for the first two IXPE pointings, taken in March 2022 (MJD 59646 to 59648 and MJD 59665 to 59667), with a synchrotron peak frequency > 1 keV. For the third IXPE pointing, in July 2022 (MJD 59769 to 59772), the synchrotron peak shifts toward lower energies and the optical/X-ray polarization degrees drop. All three IXPE epochs show an atypically low Compton dominance in the γ-rays. The X-ray polarization is systematically higher than at lower energies, suggesting an energy stratification of the jet. While during the IXPE epochs the polarization angles in the X-ray, optical, and radio bands align well, we find a clear discrepancy in the optical and radio polarization angles in the middle of the campaign. Such results further support the hypothesis of an energy-stratified jet. We modeled broadband spectra taken simultaneous to the IXPE pointings, assuming a compact zone that dominates in the X-rays and the VHE band, and an extended zone stretching farther downstream in the jet that dominates the emission at lower energies. NuSTAR data allow us to precisely constrain the synchrotron peak and therefore the underlying electron distribution. The change between the different states observed in the three IXPE pointings can be explained by a change in the magnetization and/or the emission region size, which directly connects the shift in the synchrotron peak to lower energies with the drop in the polarization degree.
MAGIC collaboration, Performance and first measurements of the MAGIC stellar intensity interferometer, published in Monthly Notices of the Royal Astronomical Society, Volume 529, Issue 4 on March 11, 2024.
In recent years, a new generation of optical intensity interferometers has emerged, leveraging the existing infrastructure of Imaging Atmospheric Cherenkov Telescopes (IACTs). The MAGIC telescopes host the MAGIC-SII system (Stellar Intensity Interferometer), implemented to investigate the feasibility and potential of this technique on IACTs. After the first successful measurements in 2019, the system was upgraded and now features a real-time, dead-time-free, 4-channel, GPU-based correlator. These hardware modifications allow seamless transitions between MAGIC’s standard very-high-energy gamma-ray observations and optical interferometry measurements within seconds. We establish the feasibility and potential of employing IACTs as competitive optical Intensity Interferometers with minimal hardware adjustments. The measurement of a total of 22 stellar diameters are reported, 9 corresponding to reference stars with previous comparable measurements, and 13 with no prior measurements. A prospective implementation involving telescopes from the forthcoming Cherenkov Telescope Array Observatory’s Northern hemisphere array, such as the first prototype of its Large-Sized Telescopes, LST-1, is technically viable. This integration would significantly enhance the sensitivity of the current system and broaden the UV-plane coverage. This advancement would enable the system to achieve competitive sensitivity with the current generation of long-baseline optical interferometers over blue wavelengths.
MAGIC collaboration, The variability patterns of the TeV blazar PG 1553 + 113 from a decade of MAGIC and multiband observations, published in Monthly Notices of the Royal Astronomical Society, Volume 529, Issue 4 on March 4, 2024.
PG 1553 + 113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high energy (VHE; >100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low- and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required.
MAGIC collaboration, First characterization of the emission behavior of Mrk 421 from radio to very high-energy gamma rays with simultaneous X-ray polarization measurements, published in Astronomy & Astrophysics, Volume 684 on April 11, 2024.
Aims. We have performed the first broadband study of Mrk 421 from radio to TeV gamma rays with simultaneous measurements of the X-ray polarization from IXPE.
Methods. The data were collected as part of an extensive multiwavelength campaign carried out between May and June 2022 using MAGIC, Fermi-LAT, NuSTAR, XMM-Newton, Swift, and several optical and radio telescopes to complement IXPE data.
Results. During the IXPE exposures, the measured 0.2–1 TeV flux was close to the quiescent state and ranged from 25% to 50% of the Crab Nebula without intra-night variability. Throughout the campaign, the very high-energy (VHE) and X-ray emission are positively correlated at a 4σ significance level. The IXPE measurements reveal an X-ray polarization degree that is a factor of 2–5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the VHE photons are emitted co-spatially with the X-rays, in the vicinity of a shock front. The June 2022 observations exhibit a rotation of the X-ray polarization angle. Despite no simultaneous VHE coverage being available during a large fraction of the swing, the Swift-XRT monitoring reveals an X-ray flux increase with a clear spectral hardening. This suggests that flares in high synchrotron peaked blazars can be accompanied by a polarization angle rotation, as observed in some flat spectrum radio quasars. Finally, during the polarization angle rotation, NuSTAR data reveal two contiguous spectral hysteresis loops in opposite directions (clockwise and counterclockwise), implying important changes in the particle acceleration efficiency on approximately hour timescales.
MAGIC collaboration, Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES 2344+514, published in Astronomy & Astrophysics, Volume 682 on February 9, 2024.
Aims. The BL Lac 1ES 2344+514 is known for temporary extreme properties characterised by a shift of the synchrotron spectral energy distribution (SED) peak energy νsynch, p above 1 keV. While those extreme states have only been observed during high flux levels thus far, additional multi-year observing campaigns are required to achieve a coherent picture. Here, we report the longest investigation of the source from radio to very high energy (VHE) performed so far, focussing on a systematic characterisation of the intermittent extreme states.
Methods. We organised a monitoring campaign covering a 3-year period from 2019 to 2021. More than ten instruments participated in the observations in order to cover the emission from radio to VHE. In particular, sensitive X-ray measurements by XMM-Newton, NuSTAR, and AstroSat took place simultaneously with multi-hour MAGIC observations, providing an unprecedented constraint of the two SED components for this blazar.
Results. While our results confirm that 1ES 2344+514 typically exhibits νsynch, p > 1 keV during elevated flux periods, we also find periods where the extreme state coincides with low flux activity. A strong spectral variability thus happens in the quiescent state, and is likely caused by an increase in the electron acceleration efficiency without a change in the electron injection luminosity. On the other hand, we also report a strong X-ray flare (among the brightest for 1ES 2344+514) without a significant shift of νsynch, p. During this particular flare, the X-ray spectrum is among the softest of the campaign. It unveils complexity in the spectral evolution, where the common harder-when-brighter trend observed in BL Lacs is violated. By combining Swift-XRT and Swift-UVOT measurements during a low and hard X-ray state, we find an excess of the UV flux with respect to an extrapolation of the X-ray spectrum to lower energies. This UV excess implies that at least two regions significantly contribute to the infrared/optical/ultraviolet/X-ray emission. Using the simultaneous MAGIC, XMM-Newton, NuSTAR, and AstroSat observations, we argue that a region possibly associated with the 10 GHz radio core may explain such an excess. Finally, we investigate a VHE flare, showing an absence of simultaneous variability in the 0.3−2 keV band. Using time-dependent leptonic modelling, we show that this behaviour, in contradiction to single-zone scenarios, can instead be explained by a two-component model.
Pace, C. M., The Solution of the Einstein’s Equations in the Vacuum Region Surrounding a Spherically Symmetric Mass Distribution, published in Journal of Modern Physics, Volume 15 on August 2024.
In this article, we address the solution of the Einstein’s equations in the vacuum region surrounding a spherically symmetric mass distribution. There are two different types of mathematical solutions, depending on the value of a constant of integration. These two types of solutions are analysed from a physical point of view. The comparison with the linear theory limit is also considered. This leads to a new solution, different from the well known one. If one considers the observational data in the weak field limit this new solution is in agreement with the available data. While the traditional Schwarzschild solution is characterized by a horizon at r=2GM/c2, no horizon exists in this new solution.
Pace, C. M., The Correct Reissner-Nordstrøm, Kerr and Kerr-Newman Metrics, published in Journal of Modern Physics, Volume 15 on September 2024.
In a very recent article of mine I have corrected the traditional derivation of the Schwarzschild metric thus arriving to formulate a correct Schwarzschild metric different from the traditional Schwarzschild metric. In this article, starting from this correct Schwarzschild metric, I also propose corrections to the other traditional Reissner-Nordstrøm, Kerr and Kerr-Newman metrics on the basis of the fact that these metrics should be equal to the correct Schwarzschild metric in the borderline case in which they reduce to the case described by this metric. In this way, we see that, like the correct Schwarzschild metric, also the correct Reissner-Nordstrøm, Kerr and Kerr-Newman metrics do not present any event horizon (and therefore do not present any black hole) unlike the traditional Reissner-Nordstrøm, Kerr and Kerr-Newman metrics.
B Eslam Panah, B Hazarika, P Phukon, Thermodynamic Topology of Topological Black Hole in F(R)-ModMax Gravity’s Rainbow, published in Progress of Theoretical and Experimental Physics, Volume 2024, Issue 8, on August 2024.
In order to include the effect of high energy and topological parameters on black holes in F(R) gravity, we consider two corrections to this gravity: energy-dependent spacetime with different topological constants, and a nonlinear electrodynamics field. In other words, we combine F(R) gravity’s rainbow with ModMax nonlinear electrodynamics theory to see the effects of high energy and topological parameters on the physics of black holes. For this purpose, we first extract topological black hole solutions in F(R)-ModMax gravity’s rainbow. Then, by considering black holes as thermodynamic systems, we obtain thermodynamic quantities and check the first law of thermodynamics. The effect of the topological parameter on the Hawking temperature and the total mass of black holes is obvious. We also discuss the thermodynamic topology of topological black holes in F(R)-ModMax gravity’s rainbow using the off-shell free energy method. In this formalism, black holes are assumed to be equivalent to defects in their thermodynamic spaces. For our analysis, we consider two different types of thermodynamic ensembles. These are: fixed q ensemble and fixed ensemble. We take into account all the different types of curvature hypersurfaces that can be constructed in these black holes. The local and global topology of these black holes are studied by computing the topological charges at the defects in their thermodynamic spaces. Finally, in accordance with their topological charges, we classify the black holes into three topological classes with total winding numbers corresponding to -1,0, and 1. We observe that the topological classes of these black holes are dependent on the value of the rainbow function, the sign of the scalar curvature, and the choice of ensembles.
J. Sedaghat, B. Eslam Panah, R. Moradi, S. M. Zebarjad & G. H. Bordbar, Quark stars in massive gravity might be candidates for the mass gap objects, published in European Physical Journal C 84 (2024) 259 on February 2024.
We have investigated the structural properties of strange quark stars (SQSs) in a modified theory of gravity known as massive gravity. In order to obtain the equation of state (EOS) of strange quark matter, we have employed a modified version of the Nambu–Jona-Lasinio model (MNJL) which includes a combination of NJL Lagrangian and its Fierz transformation by using weighting factors (1-α) and α. Additionally, we have also calculated dimensionless tidal deformability Λ in massive gravity. To constrain the allowed values of the parameters appearing in massive gravity, we have imposed the condition Λ1.4M☉ ≤ 580. Notably, in the MNJL model, the value of α varies between zero and one. As α increases, the EOS becomes stiffer, and the value of Λ increases accordingly. We have demonstrated that by softening the EOS with increasing the bag constant, one can obtain objects in massive gravity that not only satisfy the constraint Λ1.4M☉ ≤ 580, but they also fall within the unknown mass gap region (2.5 M☉ - 5 M☉). To establish that the obtained objects in this region are not black holes, we have calculated Schwarzschild radius, compactness, and ΛMTOV in massive gravity.
B. Eslam Panah, S. Zare & H. Hassanabadi, Accelerating AdS black holes in gravity’s rainbow, published in European Physical Journal C 84, 259 (2024) on March 2024.
Motivated by the effect of the energy of moving particles in C-metric, we first obtain exact accelerating black hole solutions in gravity’s rainbow. Then, we study the effects of gravity’s rainbow and C-metric parameters on the Ricci and Kretschmann scalars, and also the asymptotical behavior of this solution. Next, we indicate how different parameters of the obtained accelerating black holes in gravity’s rainbow affect thermodynamics quantities (such as the Hawking temperature, and entropy) and the local stability (by evaluating the heat capacity). In the following, we extract the geodesic equations to determine the effects of various parameters on photon trajectory in the vicinity of this black hole, as well as obtain the radius of the photon sphere and the corresponding critical impact parameter to gain insight into AdS black hole physics by adding the gravity’s rainbow to C-metric.
Behzad Eslam Panah, Analytic Electrically Charged Black Holes in F(R)-ModMax Theory, published in Progress of Theoretical and Experimental Physics, Volume 2024, Issue 2, February 2024.
Motivated by a new model of nonlinear electrodynamics known as Modified Maxwell (ModMax) theory, an exact analytical solution for black holes is obtained by coupling ModMax nonlinear electrodynamics and F(R) gravity. Then, the effects of the system’s parameters (F(R)-ModMax gravity parameters) on the event horizons are analyzed. The obtained black hole thermodynamic properties in the F(R)-ModMax theory are investigated by extracting their thermodynamic quantities such as Hawking temperature, electric charge, electric potential, entropy, and also total mass. The first law of thermodynamics for the system under study is evaluated. Next, by considering these black holes, the impacts of various parameters on both the local stability and global stability are investigated by examining the heat capacity and the Helmholtz free energy, respectively. Finally, the thermodynamic geometry of the black hole in F(R)-ModMax gravity is investigated by applying the Hendi–Panahiyan–Eslam Panah–Momennia thermodynamic metric (HPEM’s metric).
Kh Jafarzade, B Eslam Panah and M E Rodrigues, Thermodynamics and optical properties of phantom AdS black holes in massive gravity, published in Classical and Quantum Gravity, Volume 41, Number 6 on February 2024.
Motivated by high interest in Lorentz invariant massive gravity models known as dRGT massive gravity, we present an exact phantom black hole solution in this theory of gravity and discuss the thermodynamic structure of the black hole in the canonical ensemble. Calculating the conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics and the Smarr relation in the extended phase space. In addition, we investigate both the local and global stability of these black holes and show how massive parameters affect the regions of stability. We extend our study to investigate the optical features of the black holes such as the shadow geometrical shape, energy emission rate, and deflection angle. Also, we discuss how these optical quantities are affected by massive coefficients. Finally, we consider a massive scalar perturbation minimally coupled to the background geometry of the black hole and examine the quasinormal modes by employing the WKB approximation.
A. Bagheri Tudeshki, G.H. Bordbar, B. Eslam Panah, Effect of rainbow function on the structural properties of dark energy star, published in Physics Letters B Volume 848 on January 2024.
Confirming the existence of compact objects with a mass greater than 2.5 M☉ by observational results such as GW190814 makes that is possible to provide theories to justify these observational results using modified gravity. This motivates us to use gravity's rainbow, which is the appropriate case for dense objects, to investigate the dark energy star structure as a suggested alternative case to the mass gap between neutron stars and black holes in the perspective of quantum gravity. Hence, in the present work, we derive the modified hydrostatic equilibrium equation for an anisotropic fluid, represented by the extended Chaplygin equation of state in gravity's rainbow. Then, for two isotropic and anisotropic cases, using the numerical solution, we obtain energy-dependent maximum mass and its corresponding radius, and the other properties of the dark energy star including the pressure, energy density, stability, etc. In the following, using the observational data, we compare the obtained results in two frameworks of general relativity and gravity's rainbow.
B. Eslam Panah, K. Jafarzade & Á. Rincón, Three-dimensional AdS black holes in massive-power-Maxwell theory, published in General Relativity and Gravitation, Volume 56, article number 46, on April 2024.
Recently, it was shown that the power-Maxwell (PM) theory could remove the singularity of the electric field (B. Eslam Panah, Europhys. Lett. 134, 20005 (2021). Motivated by a great interest in three-dimensional black holes and a surge of success in studying massive gravity from both the cosmological and astrophysical points of view, we investigate three-dimensional black hole solutions in de Rham, Gabadadze, and Tolley massive theory of gravity in the presence of PM electrodynamics. First, we extract exact three-dimensional solutions in this theory of gravity. Then we study the geometrical properties of these solutions. Calculating conserved and thermodynamic quantities, we check the validity of the first law of thermodynamics for these black holes. We also examine the stability of these black holes in the context of the canonical ensemble. We continue calculating this kind of black hole’s optical features, such as the photon orbit radius, the energy emission rate, and the deflection angle. Considering these optical quantities, finally, we analyze the effective role of the parameters of models on them.
Shakeri, Soroush; Karkevandi, Davood RafieI, Bosonic dark matter in light of the NICER precise mass-radius measurements, published in Physical Review D, Volume 109, Issue 4 on February 2024.
We explore the presence of self-interacting bosonic dark matter (DM) within neutron stars (NSs) in light of the latest multimessenger observations of the Neutron Star Interior Composition Explorer (NICER) and LIGO/Virgo detectors. The bosonic DM is distributed as a core inside the NS or as a halo around it leading to formation of a DM admixed NS. We focus on the variation of the visible and dark radius of the mixed object due to DM model parameters and fractions. It is shown that DM core formation reduces the visible radius and the total mass pushing them below observational limits while halo formation is in favor of the latest mass-radius observations. Moreover, we scan over the parameter space of the bosonic DM model considering two nuclear matter equation of states by applying the radius, maximum mass and tidal deformability constraints. Our investigation allows for the exclusion of a range of DM fractions, self-coupling constant and sub-GeV boson masses, which limits the amount of accumulated DM to relatively low values to be consistent with astrophysical bounds. In this paper, we introduce main features of the pulse profile corresponding to the DM admixed NS as a novel observable quantity. We find that the depth of minimum fluxes in the pulse profiles crucially depends on the amount of DM around NS and its compactness. The current/future astrophysics missions may test for the possibility of the existence of DM within NSs and break the degeneracies between different scenarios via multiple observations.
Sigismondi, Costantino; De Vincenzi, Paolo, Eclipses: A Brief History of Celestial Mechanics, Astrometry and Astrophysics, published in Universe, Volume 10, Issue 2 on February 2024.
Solar and lunar eclipses are indeed the first astronomical phenomena which have been recorded since very early antiquity. Their periodicities gave birth to the first luni-solar calendars based on the Methonic cycle since the sixth century before Christ. The Saros cycle of 18.03 years is due to the Chaldean astronomical observations. Their eclipses' observations reported by Ptolemy in the Almagest (Alexandria of Egypt, about 150 a.C.) enabled modern astronomers to recognize the irregular rotation rate of the Earth. The Earth's rotation is some hours in delay after the last three millenia if we use the present rotation to simulate the 721 b.C. total eclipse in Babylon. This is one of the most important issues in modern celestial mechanics, along with the Earth's axis nutation of 18 yr (discovered in 1737), precession of 25.7 Kyr (discovered by Ipparchus around 150 b.C.) and obliquity of 42 Kyr motions (discovered by Arabic astronomers and assessed from the Middle Ages to the modern era, IX to XVIII centuries). Newtonian and Einstenian gravitational theories explain fully these tiny motions, along with the Lense–Thirring gravitodynamic effect, which required great experimental accuracy. The most accurate lunar and solar theories, or their motion in analytical or numerical form, allow us to predict—along with the lunar limb profile recovered by a Japanese lunar orbiter—the appearance of total, annular solar eclipses or lunar occultations for a given place on Earth. The observation of these events, with precise timing, may permit us to verify the sphericity of the solar profile and its variability. The variation of the solar diameter on a global scale was claimed firstly by Angelo Secchi in the 1860s and more recently by Jack Eddy in 1978. In both cases, long and accurate observational campaigns started in Rome (1877–1937) and Greenwich Observatories, as well as at Yale University and the NASA and US Naval Observatory (1979–2011) with eclipses and balloon-borne heliometric observations. The IOTA/ES and US sections as well as the ICRA continued the eclipse campaigns. The global variations of the solar diameter over a decadal timescale, and at the millarcsecond level, may reflect some variation in solar energy output, which may explain some past climatic variations (such as the Allerød and Dryas periods in Pleistocene), involving the outer layers of the Sun. "An eclipse never comes alone"; in the eclipse season, lasting about one month, we can have also lunar eclipses. Including the penumbral lunar eclipses, the probability of occurrence is equi-distributed amongst lunar and solar eclipses, but while the lunar eclipses are visible for a whole hemisphere at once, the solar eclipses are not. The color of the umbral shadow on the Moon was known since antiquity, and Galileo (1632, Dialogo sopra i Massimi Sistemi del Mondo) shows clearly these phenomena from copper color to a totally dark, eclipsed full Moon. Three centuries later, André Danjon was able to correlate that umbral color with the 11-year cycle of solar activity. The forthcoming American total solar eclipse of 8 April 2024 will be probably the eclipse with the largest mediatic impact of the history; we wish that also the scientific impulse toward solar physics and astronomy will be relevant, and the measure of the solar diameter with Baily's beads is indeed one of the topics significantly related to the Sun–Earth connections.
Prakapenia, Mikalai; Vereshchagin, Gregory, Pair Creation in Hot Electrosphere of Compact Astrophysical Objects, published in The Astrophysical Journal, Volume 963, Issue 2 on March 2024.
The mechanism of pair creation in the electrosphere of compact astrophysical objects such as quark stars or neutron stars is revisited, paying attention to evaporation of electrons and acceleration of electrons and positrons, which were previously not addressed in the literature. We perform a series of numerical simulations using the Vlasov–Maxwell equations. The rate of pair creation strongly depends on electric field strength in the electrosphere. Although Pauli blocking is explicitly taken into account, we find no exponential suppression of the pair creation rate at low temperatures. The luminosity in pairs increases with temperature and it may reach up to L ± ∼ 1052 erg s‑1, much larger than previously assumed.
Rafiei Karkevandi, Davood; Shahrbaf, Mahboubeh; Shakeri, Soroush; Typel, Stefan, Exploring the Distribution and Impact of Bosonic Dark Matter in Neutron Stars, published in Particles, Volume 7, Issue 1 on March 2024.
The presence of dark matter (DM) within neutron stars (NSs) can be introduced by different accumulation scenarios in which DM and baryonic matter (BM) may interact only through the gravitational force. In this work, we consider asymmetric self-interacting bosonic DM, which can reside as a dense core inside the NS or form an extended halo around it. It is seen that depending on the boson mass (mχ), self-coupling constant (λ) and DM fraction (Fχ), the maximum mass, radius and tidal deformability of NSs with DM admixture will be altered significantly. The impact of DM causes some modifications in the observable features induced solely by the BM component. Here, we focus on the widely used nuclear matter equation of state (EoS) called DD2 for describing NS matter. We show that by involving DM in NSs, the corresponding observational parameters will be changed to be consistent with the latest multi-messenger observations of NSs. It is seen that for mχ≳200 MeV and λ≲2π, DM-admixed NSs with 4%≲Fχ≲20% are consistent with the maximum mass and tidal deformability constraints.
Millauro, C. ; Argüelles, C. R.; Vieyro, F. L.; Crespi, V.; Mestre, M. F., Accretion discs onto supermassive compact objects: A portal to dark matter physics in active galaxies, published in Astronomy & Astrophysics, Volume 685 on May 2024.
Context. The study of the physics of the accretion discs that develop around supermassive black hole (BH) candidates provides essential theoretical tools to test their nature.
Aims: Here, we study the accretion flow and associated emission using generalised α-discs accreting onto horizonless dark compact objects in order to make comparisons with the traditional BH scenario. The BH alternative proposed here consists in a dense and highly degenerate core made of fermionic dark matter (DM) and surrounded by a more diluted DM halo. This dense core-diluted halo DM configuration is a solution of Einstein's equation of general relativity (GR) in spherical symmetry, which naturally arises once the quantum nature of the DM fermions is duly accounted for.
Methods: The methodology followed in this work consists in first generalising the theory of α-discs to work in the presence of regular and horizonless compact objects, and then applying it to the case of core-halo DM profiles typical of active-like galaxies.
Results: The fact that the compactness of the dense and transparent DM core scales with particle mass allows the following key findings of this work: (i) There is always a given core compacity - corresponding particle mass - that produces a luminosity spectrum that is almost indistinguishable from that of a Schwarzschild BH of the same mass as the DM core. (ii) The disc can enter deep inside the non-rotating DM core, allowing accretion-powered efficiencies of as high as 28%, which is comparable to that of a highly rotating Kerr BH.
Conclusions: These results, together with the existence of a critical DM core mass of collapse into a supermassive BH, open new avenues of research for two seemingly unrelated topics: AGN phenomenology and dark matter physics.
Punsly, B., First image of a jet launching from a black hole accretion system: Kinematics, published in Astronomy & Astrophysics, Volume 685 on May 2024.
Jets are endemic to both Galactic solar mass and extragalactic supermassive black holes. A recent 86 GHz image of M 87 shows a jet emerging from the accretion ring around a black hole, providing the first direct observational constraint on the kinematics of the jet-launching region in any black hole jetted system. The very wide (∼280 μas), highly collimated, limb-brightened cylindrical jet base is not predicted in current numerical simulations. The emission was shown to be consistent with that of a thick-walled cylindrical source that apparently feeds the flow that produces the bright limbs of the outer jet at an axial distance downstream of 0.4 mas < z < 0.65 mas. The analysis here applies the conservation laws of energy, angular momentum, and magnetic flux to the combined system of the outer jet, the cylindrical jet, and the launch region. It also uses the brightness asymmetries of the jet and counterjet to constrain the Doppler factor. The only global solutions have a source that is located < 34 μas from the event horizon. This includes the Event Horizon Telescope annulus of emission and the regions interior to this annulus. The axial jet begins as a magnetically dominated flow that spreads laterally from the launch radius (< 34 μas). It becomes super-magnetosonic before it reaches the base of the cylindrical jet. The flow is ostensibly redirected and collimated by a cylindrical nozzle formed in a thick accretion disk. The flow emerges from the nozzle as a mildly relativistic (0.3c < v < 0.4c) jet with a significant protonic kinetic energy flux.
Bianco, C. L.; Mirtorabi, M. T.; Moradi, R.; Rastegarnia, F.; Rueda, J. A.; Ruffini, R.; Wang, Y.; Della Valle, M.; Li, Liang; Zhang, S. R., Probing Electromagnetic Gravitational-wave Emission Coincidence in a Type I Binary-driven Hypernova Family of Long Gamma-Ray Bursts at Very High Redshift, published in The Astrophysical Journal, Volume 966, Issue 2 on May 2024.
The repointing time of the X-Ray Telescope (XRT) instrument on the Neil Gehrels Swift Observatory satellite has posed challenges in observing and studying the early X-ray emissions within ≈40 s after a gamma-ray burst (GRB) trigger. To address this issue, we adopt a novel approach that capitalizes on the cosmological time dilation in GRBs with redshifts ranging from 3 to 9. Applying this strategy to Swift/XRT data, we investigate the earliest X-ray emissions of 368 GRBs from the Swift catalog, including short and long GRBs. We compare the observed time delay between the GRB trigger and the initial Swift/XRT observation, measured in the GRB observer frame, and the corresponding cosmological rest-frame time delay (RTD). This technique is here used in the analysis of GRB 090423 at z = 8.233 (RTD ∼8.2 s), GRB 090429B at z ≈ 9.4 (RTD ∼10.1 s), and GRB 220101A at z = 4.61 (RTD ∼14.4 s). The cosmological time dilation enables us to observe the very early X-ray afterglow emission in these three GRBs. We thus validate the observation of the collapse of the carbon–oxygen core and the coeval newborn neutron star (νNS) formation triggering the GRB event in the binary-driven hypernova (BdHN) scenario. We also evidence the νNS spin-up due to supernova ejecta fallback and its subsequent slowing down due to the X-ray/optical/radio synchrotron afterglow emission. A brief gravitational-wave signal may separate the two stages owing to a fast-spinning νNS triaxial-to-axisymmetric transition. We also analyze the long GRB redshift distribution for the different BdHN types and infer that BdHNe II and III may originate the NS binary progenitors of short GRBs.
Gao, Li-Yang ; Xue, She-Sheng ; Zhang, Xin, Dark energy and matter interacting scenario to relieve H 0 and S8 tensions, published in Chinese Physics C, Volume 48, Issue 5 on May 2024.
We consider a new cosmological model (called ΛCDM), in which the vacuum energy interacts with matter and radiation, and test this model using the current cosmological observations. Using the CMB+BAO+SN (CBS) dataset to constrain the model, we find that H0 and S8 tensions are relieved to 2.87σ and 2.77σ, respectively. However, in this case, the ΛCDM model is not favored by the data, compared with ΛCDM. We find that when the H0 and S8 data are added to the data combination, the situation is significantly improved. In the CBS+ H0 case, the model relieves the H0 tension to 0.47σ, and the model is favored over ΛCDM. In the CBS+ H0 + S8 case, we obtain a synthetically best situation, in which the H0 and S8 tensions are relieved to 0.72σ and 2.11σ, respectively. In this case, the model is most favored by the data. Therefore, this cosmological model can greatly relieve the H0 tension and simultaneously effectively alleviate the S8 tension.
Xue, She-Sheng, Holographic massive plasma state in Friedman universe: cosmological fine-tuning and coincidence problems, published in Journal of Cosmology and Astroparticle Physics, Volume 2024, Issue 05 on May 2024.
Massive particle and antiparticle pair production and oscillation on the horizon form a holographic and massive pair plasma state in the Friedman Universe. Via this state, the Einstein cosmology term (dark energy) interacts with matter and radiation and is time-varying Λ̃ in the Universe's evolution. It is determined by a close set of ordinary differential equations for dark energy, matter, and radiation energy densities. The solutions are unique, provided the initial conditions given by observations. In inflation and reheating, dark energy density decreases from the inflation scale, converting to matter and radiation energy densities. In standard cosmology, matter and radiation energy densities convert to dark energy density, reaching the present Universe. By comparing with ΛCDM, quintessence and dark energy interacting models, we show that these results can be the possible solutions for cosmological fine-tuning and coincidence problems.
Mahmoudi, Somayyeh; Sadegh, Mahdi; Khodagholizadeh, Jafar; Motie, Iman; Xue, She-Sheng; Blanchard, Alain, Generation of the CMB cosmic birefringence through axion-like particles, sterile and active neutrinos, published in The European Physical Journal C, Volume 84, Issue 6 on June 2024.
The cosmic birefringence (CB) angle refers to the rotation of the linear polarization plane of Cosmic Microwave Background (CMB) radiations when parity-violating theories are considered. We analyzed the Quantum Boltzmann equation for an ensemble of CMB photons interacting with the right-handed sterile neutrino dark matter (DM) and axion-like particles (ALPs) DM in the presence of the scalar metric perturbation. We used the birefringence angle of CMB to study those probable candidates of DM. It is shown that the CB angle contribution of sterile neutrino is much less that two other sources considered here. Next, we combined the results of the cosmic neutrinos' contribution and the contribution of the ALPs to producing the CMB birefringence and discussed the uncertainty on the parameter space of axions caused by the share of CMB-cosmic neutrino interaction in generating this effect. Finally, we plotted the EB power spectrum of the CMB and showed that this spectrum behaves differently in the presence of cosmic neutrinos and ALPs interactions in small l. Hence, future observed data for CEBl, will help us to distinguish the CB angle value due to the various sources of its production.
Bini, Donato; Geralico, Andrea; Jantzen, Robert T.; Ruffini, Remo, On Fermi's Resolution of the "4/3 Problem" in the Classical Theory of the Electron, published in Foundations of Physics, Volume 54, on June 2024.
We discuss the solution proposed by Fermi to the so called "4/3 problem" in the classical theory of the electron, a problem which puzzled the physics community for many decades before and after his contribution. Unfortunately his early resolution of the problem in 1922–1923 published in three versions in Italian and German journals (after three preliminary articles on the topic) went largely unnoticed. Even more recent texts devoted to classical electron theory still do not present his argument or acknowledge the actual content of those articles. The calculations initiated by Fermi at the time are completed here by formulating and discussing the conservation of the total 4-momentum of the accelerated electron as seen from the instantaneous rest frame in which it is momentarily at rest.
Ruffini, Remo; Sigismondi, Costantino, Fitting the Crab Supernova with a Gamma-Ray Burst, published in Universe, Volume 10, Issue 7 on June 2024.
Here, we reconsider the historical data, assuming a gamma-ray burst (GRB) as its source. A Supernova correlated with the GRB explains well the fading time observed by the ancient Chinese astronomers in the daytime and the nighttime, while the GRB power law explains the present X-rays and GeV emission of the Crab. On the grounds of a recent understanding of the first episode of binary-driven hypernova GRB (BDHN GRB) in terms of the collapse of a ten solar masses core, we propose the possible identification of the real Supernova event at an earlier time than Chinese chronicles. This work allows a new understanding of the significance of historical astronomical observations, including a fireball due to gamma-ray air shower observation and a plague of acute radiation syndrome, documented with several thousands of victims in the Eurasian area (Egypt, Iraq, and Syria).
Zhang, Shu-Rui; Prakapenia, Mikalai, The transformation of the rotational energy of a Kerr black hole, published in Classical and Quantum Gravity, Volume 41, Issue 13 on July 2024.
This paper analyzes the feedback of the rotational energy extraction from a Kerr black hole (BH) by the 'ballistic method', i.e. the test particle decay in the BH ergosphere pioneered by Roger Penrose. The focus is on the negative energy counterrotating particles (which can be massive or massless) going in towards the horizon, and the feedback on the BH irreducible mass is assessed. Generally, the change in irreducible mass is a function of the conserved quantities of the particle. For an extreme Kerr BH and in the limit , all the reduced transformable energy goes into the irreducible mass (i.e. ), resulting in high irreversibility. The amount of extracted energy from the BH using test particles is much lower than the change of transformable energy. For non-extreme Kerr BHs, the effective potential of particle motion on the equatorial plane in Kerr spacetime is analyzed, and it is demonstrated that the Penrose process can only be undergone by BHs with a dimensionless spin if the decay point coincides with the turning point. Based on that, the lower limit of the change in irreducible mass is provided as a function of the dimensionless spin of the BH. The significance of the increase in the irreducible mass of the BH during the energy extraction process is generally and concisely illustrated by introducing the concept of transformable energy of the BH. The feedback from the Penrose process on the irreducible mass demonstrates the irreversibility of energy extraction and highlights that the total amount of energy that can be extracted from a BH is less than previously anticipated.
Gao, Hao-Xuan; Geng, Jin-Jun; Sun, Tian-Rui; Li, Liang; Huang, Yong-Feng; Wu, Xue-Feng, Probing Thermal Electrons in Gamma-Ray Burst Afterglows, published in The Astrophysical Journal, Volume 971, Issue 1 on August 2024.
Particle-in-cell simulations have unveiled that shock-accelerated electrons do not follow a pure power-law distribution, but have an additional low-energy "thermal" part, which owns a considerable portion of the total energy of the electrons. Investigating the effects of these thermal electrons on gamma-ray burst (GRB) afterglows may provide valuable insights into the particle acceleration mechanisms. We solve the continuity equation of electrons in energy space, from which multiwavelength afterglows are derived by incorporating processes including synchrotron radiation, synchrotron self-absorption, synchrotron self-Compton scattering, and γ–γ annihilation. First, there is an underlying positive correlation between the temporal and spectral indices due to the cooling of electrons. Moreover, thermal electrons result in simultaneous nonmonotonic variations of both the spectral and temporal indices at multiple wavelengths, which could be individually recorded by the 2.5 m Wide Field Survey Telescope and Vera Rubin Observatory Legacy Survey of Space and Time (LSST). The thermal electrons could also be diagnosed using afterglow spectra from synergistic observations in the optical (with LSST) and X-ray (with the Microchannel X-ray Telescope on board the Space Variable Objects Monitor) bands. Finally, we use Monte Carlo simulations to obtain the distribution of the peak flux ratio (RX) between the soft and hard X-rays, and of the time delay (Δt) between the peak times of the soft X-ray and optical light curves. The thermal electrons significantly raise the upper limits of both RX and Δt. Thus, the distribution of GRB afterglows with thermal electrons is more scattered in the RX‑Δt plane.
Ajmal, S.; Gaglione, J. T.; Gurrola, A.; Panella, O.; Presilla, M.; Romeo, F.; Sun, H.; Xue, S. -S., Searching for exclusive leptoquarks with the Nambu-Jona-Lasinio composite model at the LHC and HL-LHC, published in Journal of High Energy Physics, Volume 2024, Issue 8 on August 2024.
We present a detailed study concerning a new physics scenario involving four fermion operators of the Nambu-Jona-Lasinio type characterized by a strong-coupling ultraviolet fixed point where composite particles are formed as bound states of elementary fermions at the scale Λ=OTeV. After implementing the model in the Universal FeynRules Output format, we focus on the phenomenology of the scalar leptoquarks at the LHC and the High-Luminosity option. Leptoquark particles have undergone extensive scrutiny in the literature and experimental searches, primarily relying on pair production and, more recently, incorporating single, Drell-Yan t-channel, and lepton-induced processes. This study marks, for the first time, the examination of these production modes at varying jet multiplicities. Novel mechanisms emerge, enhancing the total production cross section. A global strategy is devised to capture all final state particles produced in association with leptoquarks or originating from their decay, which we termed "exclusive", in an analogy to the nomenclature used in nuclear reactions. The assessment of the significance in current and future LHC runs, focusing on the case of a leptoquark coupling to a muon–c quark pair, reveals greater sensitivity compared to ongoing searches. Given this heightened discovery potential, we advocate the incorporation of exclusive leptoquark searches in future investigations at the LHC.
Della Valle, Massimo; Shafter, Allen W.; Starrfield, Sumner, Jet-induced Enhancement of the Nova Rate in M87, published in Research Notes of the AAS, Volume 8, Issue 8, on August 2024.
We argue that the Bondi accretion mechanism has the potential to enhance classical nova production near the M87 jet. According to our estimates, the jet's influence can increase the nova rate in its vicinity by up to a factor of two over the background rate by triggering explosions on single white dwarfs. This result may offer a straightforward explanation for the recently observed excess of novae near the M87 jet.
Mestre, Martín Federico; Argüelles, Carlos Raul; Carpintero, Daniel Diego; Crespi, Valentina; Krut, Andreas, Modeling the track of the GD-1 stellar stream inside a host with a fermionic dark matter core-halo distribution, published in Astronomy & Astrophysics, Volume 68 on September 2024.
Context. Traditional studies of stellar streams typically involve phenomenological ΛCDM halos or ad hoc dark matter (DM) profiles with different degrees of triaxiality, which preclude us from gaining insights into the nature and mass of the DM particles. Recently, the maximum entropy principle of halo formation has been applied to provide a DM halo model that incorporates the fermionic (quantum) nature of the particles while leading to DM profiles that depend on the fermion mass. These profiles develop a more general "dense core – diluted halo" morphology that can explain the Galactic rotation curve, while the degenerate fermion core can mimic the central massive black hole (BH). Aims. We model the GD-1 stellar stream using a spherical core-halo DM distribution for the host that simultaneously explains the dynamics of the S-cluster stars through its degenerate fermion core without a central BH. Methods. We used two optimization algorithms in order to fit both the initial conditions of the stream orbit and the fermionic model. We modeled the baryonic potential with a bulge and two disks (thin and thick) with fixed parameters according to the recent literature. The stream observables were 5D phase-space data from the Gaia DR2 survey. Results. We were able to find good fits for both the GD-1 stream and the S-stars for a family of fermionic core-halo profiles parameterized by the fermion mass. The particle masses are constrained in the range 56 keV c‑2, with a corresponding DM core of ∼103 Schwarzschild radii, to 360 keV c‑2, which corresponds to the most compact core of 5 Schwarzschild radii prior to the gravitational collapse into a BH of about 4 × 106 M⊙. Conclusions. This work provides evidence that the fermionic profile is a reliable model for the massive central object and for the DM of the Galaxy. Remarkably, this model predicts a total Milky Way mass of 2.3 × 1011 M⊙, which agrees with recent mass estimates obtained from Gaia DR3 rotation curves (Gaia RC). In summary, with one single fermionic model for the DM distribution of the Milky Way, we obtain a good fit on three totally different distance scales of the Galaxy: ∼10‑6 kpc (central, S-stars), ∼14 kpc (middle, GD-1), and ∼30 kpc (boundary, Gaia RC mass estimate).
Li, Liang; Wang, Yu, GRB 190114C: Fireball Energy Budget and Radiative Efficiency Revisited, published in The Astrophysical Journal, Volume 972, Issue 2 on September 2024.
The jet composition of gamma-ray bursts (GRBs), as well as how efficiently the jet converts its energy to radiation, are long-standing problems in GRB physics. Here, we reported a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its high fluence (∼4.4 × 10‑4 erg cm‑2) allows us to conduct the time-resolved spectral analysis in great detail and study their variations down to a very short timescale (∼0.1 s) while preserving a high significance. Its prompt emission consists of three well-separated pulses. The first two main pulses (P1 and P2) exhibit independently strong thermal components, starting from the third pulse (P3) and extending to the entire afterglow, the spectra are all nonthermal, and the synchrotron plus Compton upscattering model well interprets the observation. By combining the thermal (P1 and P2) and the nonthermal (P3) observations based on two different scenarios (global and pulse properties) and following the method described in Zhang et al., we measure the fireball parameters and GRB radiative efficiency with little uncertainties for this GRB. A relevantly high GRB radiative efficiency is obtained based on both the global and pulse properties, suggesting that if GRBs are powered by fireballs, the efficiency can sometimes be high. More interestingly, though the observed parameters are individually different (e.g., the amount of mass loading M), the radiative efficiency obtained from P1 (ηγ = 36.0% ± 6.5%) and P2 (ηγ = 41.1% ± 1.9%) is roughly the same, which implies that the central engine of the same GRB has some common properties.
Moradi, R.; Rastegarnia, F.; Wang, Y.; Mirtorabi, M. T., FNet II: spectral classification of quasars, galaxies, stars, and broad absorption line (BAL) quasars, published in Monthly Notices of the Royal Astronomical Society, Volume 533, Issue 2 on September 2024.
In this work, we enhance the FNet, a 1D convolutional neural network (CNN) with a residual neural network (ResNet) architecture, to perform spectral classification of quasars, galaxies, stars, and broad absorption line (BAL)-quasars in the SDSS-IV catalogue from DR17 of eBOSS. Leveraging its convolutional layers and the ResNet structure with different kernel sizes, FNet autonomously identifies various patterns within the entire sample of spectra. Since FNet does not require the intermediate step of identifying specific lines, a simple modification enabled our current network to classify all SDSS spectra. This modification involves changing the final output layer from a single value (redshift) to multiple values (probabilities of all classes), and accordingly adjusting the loss function from mean squared error to cross-entropy. FNet achieves a completeness of 99.00 per cent ± 0.20 for galaxies, 98.50 per cent ± 0.30 for quasars, 99.00 per cent ± 0.18 for BAL-quasars, and 98.80 per cent ± 0.20 for stars. These results are comparable to those obtained using QuasarNET, a standard CNN employed in the SDSS routine, comprises convolutional layers without the ResNet structure with equal kernel sizes, and is utilized for redshift measurement and classification by identifying seven emission lines. QuasarNET, in order to overcome the problem of finding a C IV emission line with broad absorption which is slightly more challenging than that of detecting emission lines requires to add BAL C IV line to the list of lines that the network learns to identify. However, this procedure is not necessary in FNet as it learns the features through a self-learning procedure.
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