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  ICRANet Newsletter
ICRANet Newsletter
October - November 2024
SUMMARY
1. Two recent ICRANet papers 2. ICRANet GCN 3. The conference “High Energy Astrophysics and Cosmology in the era of all-sky surveys meeting (HEACOSS)”, October 7-11, 2024, Yerevan (Armenia) 4. The “3rd Julio Garavito Armero meeting”, November 12-15, 2024, Bogotà and Bucaramanga (Colombia) 5. Prof. Ruffini participation in the “MDPI 2024 Nobel Prize in Physics Prediction Roundtable Forum”, October 8, 2024, online 6.Prof. Ruffini participation in “Complex Systems in Medicine and Posturology”, November 8, 2024, Novedrate (Italy and online) 7.Prof. Ruffini meets H.E. Fabrizio Nicoletti, Ambassador of Italy to Panama, November 15, 2024, Panama City (Panama) 8. “Mersenne prizes 2023 and 2024”, October 29, 2024, online meeting 9. A pinhole meridian line of 1780-rediscovered 10.“Marco Polo and the New Cosmography”: exhibition and conference for the 700thanniversary of his death, October 23-25, 2024, National Academy of Lincei 11. Solar Astrophysics and Relativity School, October – November 2024 12.Scientific visits to ICRANet 13. Recent publications
1.Two recent ICRANet papers
Remo Ruffini, Mikalai Prakapenia, Hernando Quevedo, Shurui Zhang, On the single versus the repetitive Penrose process in a Kerr black hole, accepted for publication by Physical Review Letters.
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.
R. Ruffini, C.L. Bianco, M. Prakapenia, H. Quevedo, J.A. Rueda, S.R. Zhang, The role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole, submitted to Physical Review Letters, accepted for publication.
The concept of the irreducible mass (Mirr) has led to the mass-energy (M) formula of a Kerr black hole (BH), in turn leading to its surface area S=16πM2irr. This also allowed the coeval identification of the reversible and irreversible transformations, soon followed by the concepts of "extracted" and "extractable" energy. This new conceptual framework avoids inconsistencies recently evidenced in a repetitive Penrose process. We consider repetitive decays in the ergosphere of an initially extreme Kerr BH and show the processes are highly irreversible. For each decay, the particle that the BH captures causes an increase of the irreducible mass (so the BH horizon), much larger than the extracted energy. The energy extraction process stops {when the BH reaches a positive spin lower limit set by the process boundary conditions}. Thus, the reaching of a final non-rotating Schwarzschild BH state through this accretion process is impossible. We have assessed such processes for selected decay radii and incoming particle with rest mass 1% of the BH initial mass M0. For r=1.2M and 1.9M, the sequence stops after 8 and 34 decays, respectively, at a spin 0.991 and 0.857, the energy extracted has been only 1.16%, and 0.42%, the extractable energy is reduced by 17% and 56%, and the irreducible mass increases by 5% and 22%, all values in units of M0. These results show the highly nonlinear change of the BH parameters, dictated by the BH mass-energy formula, and that the BH rotational energy is mainly converted into irreducible mass. Thus, evaluating the irreducible mass increase in any energy extraction processes in the Kerr BH ergosphere is mandatory.
2.ICRANet GCN
GCN Circular 37964
Subject: GRB 241025A: The discovery of a BdHN I from data of Swift, Fermi, SVOM and Einstein Probe telescopes Date: 2024-10-30T12:11:00Z (15 days ago) From: Remo Ruffini at ICRA
R. Ruffini, L. Becerra, C.L. Bianco, M. Della Valle, Liang Li, G.J. Mathews, M.T. Mirtorabi, R. Moradi, F. Rastegar Nia, J.A. Rueda and Y. Wang
We are comparing and contrasting the seven episodes of BdHN I observed in GRB 241025A with Eiso = 5.5 x 10^53 erg (GCN 37927) and GRB 220101A with Eiso = 3.7 x 10^54 erg (GCN 31365). Both are highly energetic and located at a redshift greater than 4 (GCN 37866, GCN 31353), which allows a zoom-in investigation due to cosmological expansion. By examining the onset of black hole formation and the ultra-relativistic prompt emission (UPE), we gain insight into the rotational dynamics within these systems. This investigation requires additional observational data, particularly optical emission measurements from the newly born pulsar and extended X-ray afterglow data up to more than 10^6 seconds. Concurrent monitoring by Fermi-LAT will be crucial for capturing high-energy emissions, while the already performed Fermi-GBM observations enable the identification of the jetted emission. On this basis, the energy extraction process from a newly formed black hole will be determine.
3.The conference “High Energy Astrophysics and Cosmology in the era of all-sky surveys” (HEACOSS), October 7-11, 2024, Yerevan (Armenia)
From October 7 to 11, 2024, Prof. Ruffini (Director of ICRANet) and Prof. Gregory Vereshchagin (ICRANet Faculty Professor), have been invited to present lectures on the occasion of the “High Energy Astrophysics and Cosmology in the era of all-sky surveys meeting” (HEACOSS 2024), held in Yerevan (Armenia) from October 7 to 11, 2024. The meeting has been organized by profs. Narek Sahakyan, Director of ICRANet center in Yerevan and Marat Gilfanov (MPA, Germany).
The main goal of the meeting was to review and discuss the recent achievements in high energy astrophysics and cosmology in the context of these developments. It focused on astrophysics of compact objects on all mass scales, formation and growth of supermassive black holes, non-stationary and transient phenomena in the vicinity of compact objects and selected themes of physical cosmology. The physics of jets in blazars and gamma-ray bursts has been also addressed, exploring the mechanisms and consequences of these extreme events.
The start of the 21st century was marked with the advent of all-sky surveys at all wavelengths, from radio to X-ray and Gamma-ray. Together with recent breakthroughs in large-volume ice neutrino detectors, and the successful detection of astrophysical gravitational waves, these pivotal advancements are giving rise to multi-messenger astrophysics setting the stage for new theoretical challenges.
On the occasion of the meeting, Prof. Ruffini presented a plenary lecture titled “Black holes all over the Universe” and Prof. Vereshchagin presented a talk titled “Electron-positron pair creation in electrosphere of compact astrophysical objects”.
Prof. Ruffini’s abstract: “We were quite fortunate with John Wheeler introducing the concept of Black Hole (BH) and more important using the Kerr mathematical solution to find the BH mass energy formula with Christodoulou and Hawking. We have been equally fortunate to participate in developing the largest observational effort extending to the earliest million years from the Big Bang and observing BH in all range of Masses from 10 to 10+11 Solar masses (SMBH). In all this the development of the Binary Driven Hypernova model based on a simple CO core of 10 Msun and a companion binary NS , with its seven Episodes, is guiding to establishing new physical laws in yet unobserved extragalactic systems and, equally important in challenging and were appropriate,dismantling some of the acquired astrophysical knowledge in our Galaxy. We are further expanding the understanding of the BDHN model at earlier times. We are using this acquired knowledge in:1) probing how to extend these results to SMBH in active galactic nuclei; 2) in identifying one of the most elusive components to identify the origin of SMBH. We proceed by accurately studying the physics ongoing in our galactic Cente; 3) we need to further comprehend the fundamental role of the 4 parameters of a BH : mass, charge, angular momentum and irriducible mass which severely limit the possibility of extracting energy from a BH or a SMBH using gravitational non linear interactions while allowing the, same processes, to proceed with more elementary linear interactions.This is crucial to understand the inner structure of our Universe”.
Prof. Vereshchagin’s presented a plenary lecture titled “Electron-positron pair creation in electrosphere of compact astrophysical objects”. His abstract is: “We will discuss pair creation by electrically neutral compact astrophysical objects, having sufficiently sharp positively charged surface boundary to create an electrosphere with overcritical electric field. Two types of energy sources will be considered: heat and radial electromagnetic perturbation. Implications for astrophysical observations will be outlined”.
The website of the meeting: https://indico.cern.ch/event/1382899/overview
4.The “3rd Julio Garavito Armero meeting”, November 12-15, 2024, Bogotà and Bucaramanga (Colombia)
The 3rd Julio Garavito Armero meeting has been held from November 12 to 15, 2024 at the Pontificia Universidad Javeriana in Bogotá as well as at the Universidad Industrial de Santander (UIS) in Bucaramanga (Colombia). This scientific meeting, co-organized by ICRANet, by the Halley Group ofUIS and by the Pontificia Universidad Javeriana, followed 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/Julio_Garavito.
The3rd Julio Garavito meeting reflected once again the continuous commitment in the scientific cooperation between ICRANet and Colombian Universities and research centers.Itcovered 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 have been also explored.
The inauguration of the 3rdJulio Garavito meeting took place on Tuesday, November 12, 2024, at the Pontificia Universidad Javerianain Bogotá. On that day, the opening ceremony was held in the Carlos Corredor Auditorium, starting with some remarks by the President Luis Fernando Munera and by Prof. Nelson Velandia. This speech was followed by lectures offered by Profs. Remo Ruffini (Director of ICRANet), Prof. Jorge Rueda (ICRANet Faculty Professor), Laura Marcela Becerra Bayona (ICRANet Adjunct Professor), Carlos Raul Arguelles (ICRANet Adjunct Professor), Luis Nunez (UIS) and Massimo Della Valle (ICRANet Faculty Professor).
From November 13 to 15, the meeting moved to UIS in Bucaramanga. It offered a rich agenda of activities including meetings, conferences and keynote lectures, allowing attendees to delve into cutting-edge topics in the field of astronomy and physics.The program of the meeting was articulated in 8 plenary lectures (delivered by Profs. Remo Ruffini, Jorge Rueda, Carlos Raul Arguelles,Massimo Della Valle, Francisco Frutos-Alfaro, Juan Diego Soler, Justo Ospino, Jose David Sanabria Gomez), 21 talks parallel sessions and 3 talks on artificial intelligence and astrophysics.
Concerning the proceedings, selected papers will be published in La Revista de la Academia Colombiana de Ciencias Exactas, Físicas y Naturales (https://raccefyn.co/index.php/raccefyn) as well as in Science in Development, Universidad Pedagógica y Tecnológica de Colombia. (https://revistas.uptc.edu.co/index.php/ciencia_en_desarrollo/issue/view/853).
The website of the meeting: https://jupyterhd.redclara.net/event/47/overview
The news on UIS website: https://comunicaciones.uis.edu.co/inicia-el-3er-encuentro-internacional-julio-garavito-en-la-uis/
5.Prof. Ruffini participation in “MDPI 2024 Nobel Prize in Physics Prediction Roundtable Forum”, October 8, 2024
On October 8, 2024, Prof. Ruffini (Director of ICRANet) has been invited to participate as a speaker in the “MDPI 2024 Nobel Prize in Physics Prediction” roundtable forum.
Coinciding with the announcement of the 2024 Nobel Prize in Physics, this forum underscored the importance of recognizing outstanding achievements that push the boundaries of human knowledge and understanding. It was a valuable opportunity to exchange ideas on the advancements driving scientific progress and to inspire the next generation of gifted physicists.
General topics of discussion during the event included: breakthrough research shaping the future of physics; reflecting on past Nobel-Prize-winning work and its legacy; the key trends driving innovation in physics today; as well as exploring the societal and scientific contributions of physics research.
In addition to prof. Remo Ruffini, the other invited speakers who joined the forum were Dr. Arias Felicitas (Observatoire de Paris - SYRTE, France) and Prof. Dr. Costas Varotsos (National and Kapodistrian University of Athens, Greece).
The website of the forum: https://sciforum.net/event/NPR2024?section=#webnar_recording
The recording of the forum: https://www.youtube.com/watch?v=Y9_puAY2_dM&t=961s
6.Prof. Ruffini participation in “Complex Systems in Medicine and Posturology”, November 8, 2024, Novedrate (Italy and online)
On November 8, 2024, Prof. Ruffini (Director of ICRANet) has been invited to participate as a speaker in the meeting “Complex Systems in Medicine and Posturology”. This international meeting, organized by the eCAMPUS University, has been held both at Auditorium of eCampus University in Novedrate (Italy) and online. It celebrated the publication of the book “Complex Systems in Medicine” by Prof. Raoul Saggini and Prof. Livio Giuliani (eCAMPUS University)
On that occasion, Prof. Ruffini presented a talk titled “Black Holes all over the Universe”. Here is the abstract:“We were quite fortunate with John Wheeler introducing the concept of Black Hole (BH) and more important using the Kerrr mathematical solution to find the BH mass energy formula with Christodoulou and Hawking. We have been equally fortunate to participate in developing the largest observational effort extending to the earliest million years from the Big Bang and observing BH in all range of Masses from 10 to 10+11 Solar masses (SMBH). In all this the development of the Binary Driven Hypernova model based on a simple CO core of 10 Msun and a companion binary NS , with its seven Episodes, is guiding to establishing new physical laws in yet unobserved extragalactic systems and, equally important in challenging and were appropriate,dismantling some of the acquired astrophysical knowledge in our Galaxy. We are further expanding the understanding of the BDHN model at earlier times. We are using this acquired knowledge in:1) probing how to extend these results to SMBH in active galactic nuclei; 2) in identifying one of the most elusive components to identify the origin of SMBH. We proceed by accurately studying the physics ongoing in our galactic Cente; 3) we need to further comprehend the fundamental role of the 4 parameters of a BH : mass, charge, angular momentum and irriducible mass which severely limit the possibility of extracting energy from a BH or a SMBH using gravitational non linear interactions while allowing the, same processes, to proceed with more elementary linear interactions.This is crucial to understand the inner structure of our Universe”
The announcement of the meeting: https://www.universidadecampus.es/en/university/events/complex-systems-in-medicine-and-posturology/index.html
7.Prof. Ruffini participation in “Complex Systems in Medicine and Posturology”, November 8, 2024, Novedrate (Italy and online)
On November 15, 2024, Prof. Ruffini (Director of ICRANet), together with Prof. Massimo Della Valle (Chairman ICRANet Scientific Committee), met the Ambassador Extraordinary and Plenipotentiary of Italy to Panama, H.E. Fabrizio Nicoletti as well as Dr Andrea De Melis (commercial and cultural attaché of the Italian Embassy in Panama) at the seat of the Italian Embassy in Panama City.
On the occasion of an official lunch, Prof. Ruffini illustrated to Ambassador Nicoletti ICRANet current activities, its main research topics as well as the all the recent scientific results. The current projects implemented by the ICRANet Hq in Pescara as well as with all ICRANet Seats and associated centers, have been presented and discussed. The important role played by ICRANet in daily fostering scientific exchanges worldwide and establishing agreements with the major Universities and research Institutes worldwide was also highlighted.
Both parties strongly highlighted the importance of the Latin American - Italian scientific cooperation in the field of astrophysics and discussed the possibilities of further develop and expand it in the region, under the guide of ICRANet.
8.“Mersenne prizes 2023 and 2024”, October 29, 2024, online meeting
On October 29 at h 6 PM, Prof. Costantino announced the attribution of the Mersenne Prizes 2023 and 2024, on the occasion of the first session of the Solar astronomy school (see the following news).
Inspired by the figure of Marino Mersenne (1588-1648), than European referent for all the scientists, ICRANet promoted and established this prize in 2019, with the sponsorship of the IAU Commission on History of Astronomy (Commission C3) and ideally continues his work in the field of Relativistic Astrophysics, representing a strong network of scientists from all over the world.
The students awarded for the 2023 edition were:
The students awarded for the 2024 edition were:
9.A pinhole meridian line of 1780-rediscovered
On October 25, 2024, Prof. Nicoletta Lanciano (Sapienza University) presented her studies on that meridian line, built by the Jesuit André Febres in the summer of 1780.It is a mini replica 1:21 of the great meridian line of S. Maria degli Angeli (1702), with the addition of a 2x4 meters complete Italian sundial carved on the floor's marble.
The meridian line is in a room at the last floor of the Palazzo Mattei di Giove, the one of the Modern History Library's Director, in good state of conservation.
N. Lanciano, Angelo Bruno (Difesa), Claudio Costa (Specola Vaticana) and Costantino Sigismondi (ICRANet Adjunct Professor) went to measure the alignment with the celestial North on November 7, 2024, with the method of 4 contemporary transits obtained from 4 pinholes vertically aligned, invented by Sigismondi. This meridian line was found 12'+/-1' Eastward rotated, corresponding to a maximum of 6 mm of deviation over 2 meters.This value reflects the astrometric theory and technology available at that time, in Rome, for an educated Jesuit, during the period (1773-1814) in which the Jesuits were suppressed and the members put in prison or clandestine.
The author built this instrument in summer, extrapolating short shadows, while in winter he could have achieved a better precision. Moreover, the noon reference timing available to André Febres was also probably slightly in delay as the one of S. Maria degli Angeli.
10.“Marco Polo and the New Cosmography”: exhibition and conference for the 700th anniversary of his death, October 23-25, 2024, National Academy of Lincei
From October 23 to 25, 2024, Prof. Costantino Sigismondi (ICRANet Adjunct Professor), attended the event “Marco Polo and the New Cosmography” at the National Academy of Lincei, filtering the multidisciplinary information that was dispensed at this prestigious event with the eye of the historian of astronomy.
The figure of Marco Polo was also placed in parallel with the other great Italian discoverer, Christopher Columbus, who based many of his insights on the text of Polo.Merchandise, mineralogy, zoology, botany, anthropology, history of religions, ethnology, geography, cosmography, history, history of customs, coining of new words, dissemination of the text in manuscript and then in print (Devisementdou Monde, the first Franco-Italian version, and Milione, also in 14th-century Tuscan... ) epigones (from Odorico da Pordenone to Antonio Pigafetta) and predecessors (the Franciscans, as well as his father and uncle)... The fact that ‘travel notes’ did not exist at the time, while commodity fees were realized in Venice itself... a series of news, very difficult to find all together except in this three-day conference.
Geography and cosmography experienced a revolution after Marco Polo's travel; the study of Fra Mauro's world map, edited by Prof. Cosimo Palagiano, Linceo, is carried out by means of a life-size copy of the map owned by CNR.In 1430, Fra Mauro, which gained a crater on the moon visited by the Apollo 17 astronauts in 1972, studied at the Camaldolese monastery in Venice all the data provided by Marco Polo with which he integrated and overtook the Ptolemaic Ecumène.His goal, which was largely shared by the Serenissima Republic of Venice, was to find the shortest and safest route for trade with the Far East. The creation of a map where the mirabilia added by the pen of Rustichello da Pisa (who shared a year's imprisonment in Genoa with Marco Polo during the writing of Il Milione) were expunged, but the useful information were kept, was a challenge whichupdated cartography up to 1200 years after Ptolemy.
Martellus's work in Florence (1490) took up everything between Mauro and Marco Polo, moving the boundaries of the Ecumène up to 270° from the meridian of the Isle of Iron, i.e. only 70° from the Azores... transforming -conceptually- the Atlantic Ocean into a new ‘Mediterranean’. Christopher Columbus' enterprise, through the -still debated- astronomer Toscanelli, fits into this new vision of the World, which has its roots in Marco Polo's travel.
The wealth of documentation on display during this exhibition reflects the structure of the conference, which closes the celebrations for the 700th anniversary of the death of Marco Polo.The context of the Library of the National Academy of Lincei, with its astronomical relics, makes the exhibition a must for anyone wanting to understand this part of the history of our civilization.
The exhibition will be open until January 26, 2025.
Photos of the inauguration day are available at the following link:https://1drv.ms/f/s!AtuZJVIfwaPjk-tGV_3g8l712-rrQg
11.Solar Astrophysics and Relativity School, October – November 2024
On October and November 2024, Prof. Costantino Sigismondi has co-organized with ICRANet a special school on Solar Flares for the student of the High School Galileo Galilei of Pescara.
The first meeting has been held at ICRANet center in Pescara on September 27, 2024, with solar observations in white light. The following meetings have been held online on October 29 on “Flares Math and Energy”, on November 7 on “Sympathetic Flares”, on November 14 on “Flares Precursors” and on November 21 on “Flares Energy Scaling”. Here below the videos of the lessons:
These meetings have been entirely dedicated to the study of solar flares in H-alpha and X-ray, through satellite data and telescopes' network.
This school, directed by Prof. Sigismondi and hold in collaboration with the Asiago Astrophysical Observatory of Padova University and the AGOSTO (Asiago Group Of Solar Transient Observers) washeld during the 11-year maximum of solar activity of the cycle XXV, occurring now on 2024-2025.The solar activity consists in a very high number of sunspots, a large area of plages and a large number of flares, many of them being sympathetic, many prominences and filaments, and some Coronal Mass Ejections.The consequences of these CME investing the Earth's magnetosphere are the boreal aurorae, that have been visible down to our Mediterranean latitudes (May 11 and October 11, 2024).Between October and November 2024, the Sun released several X-class flares, showed some days with sunspot number SSN>200 and produced a potent geomagnetic storm around October 11, experiencing some days of intense flaring activity with all the solar active surface causally connected.
12.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.
13.Recent publications
Pereira, Jonas P.; Ottoni, Tulio; Coelho, Jaziel G.; Rueda, Jorge A.; de Lima, Rafael C. R., Impact of stratified rotation on the moment of inertia of neutron stars, accepted for publication in Physical Review D.
Rigid (Uniform) rotation is usually assumed when investigating the properties of mature neutron stars (NSs). Although it simplifies their description, it is an assumption because we cannot observe the NS's innermost parts. Here, we analyze the structure of NSs in the simple case of ''almost rigidity,'' where the innermost and outermost parts rotate with different angular velocities. This is motivated by the possibility of NSs having superfluid interiors, phase transitions, and angular momentum transfer during accretion processes. We show that, in general relativity, the relative difference in angular velocity between different parts of an NS induces a change in the moment of inertia compared to that of rigid rotation. The relative change depends nonlinearly on where the angular velocity jump occurs inside the NS. For the same observed angular velocity in both configurations, if the jump location is close to the star's surface-which is possible in central compact objects (CCOs) and accreting stars-the relative change in the moment of inertia is close to that of the angular velocity (which is expected due to total angular momentum aspects). If the jump occurs deep within the NS, for instance, due to phase transitions or superfluidity, smaller relative changes in the moment of inertia are observed; we found that if it is at a radial distance smaller than approximately 40% of the star's radius, the relative changes are negligible. Additionally, we outline the relevance of systematic uncertainties that nonrigidity could have on some NS observables, such as radius, ellipticity, and the rotational energy budget of pulsars, which could explain the X-ray luminosity of some sources. Finally, we also show that non-rigidity weakens the universal I-Love-Q relations.
Rueda, J. A.; Ruffini, R., Kerr black hole energy extraction, irreducible mass feedback, and the effect of captured particles charge, accepted for publication in The European Physical Journal C.
We analyze the extraction of the rotational energy of a Kerr black hole (BH) endowed with a test charge and surrounded by an external test magnetic field and ionized low-density matter. For a magnetic field parallel to the BH spin, electrons move outward (inward) and protons inward (outward) in a region around the BH poles (equator). For zero charge, the polar region comprises spherical polar angles −60∘≲θ≲60∘ and the equatorial region 60∘≲θ≲120∘. The polar region shrinks for positive charge, and the equatorial region enlarges. For an isotropic particle density, we argue the BH could experience a cyclic behavior: starting from a zero charge, it accretes more polar protons than equatorial electrons, gaining net positive charge, energy, and angular momentum. Then, the shrinking(enlarging) of the polar(equatorial) region makes it accrete more equatorial electrons than polar protons, gaining net negative charge, energy, and angular momentum. In this phase, the BH rotational energy is extracted. The extraction process continues until the new enlargement of the polar region reverses the situation, and the cycle repeats. We show that this electrodynamical process produces a relatively limited increase of the BH irreducible mass compared to gravitational mechanisms like the Penrose process, hence being a more efficient and promising mechanism for extracting the BH rotational energy.
Becerra, L. M.; Cipolletta, F.; Fryer, C. L.; Menezes, Débora P.; Providência, Constança; Rueda, J. A.; Ruffini, R., Occurrence of gravitational collapse in the accreting neutron stars of binary-driven hypernovae, published in The Astrophysical Journal, Volume 976, Number 1 on November 14, 2024.
The binary-driven hypernova (BdHN) model proposes long gamma-ray bursts (GRBs) originate in binaries composed of a carbon–oxygen (CO) star and a neutron star (NS) companion. The CO core collapse generates a newborn NS and a supernova that triggers the GRB by accreting onto the NSs, rapidly transferring mass and angular momentum to them. This article aims to determine the conditions under which a black hole (BH) forms from NS collapse induced by the accretion and the impact on the GRB's observational properties and taxonomy. We perform three-dimensional, smoothed particle hydrodynamics simulations of BdHNe using up-to-date NS nuclear equations of state, with and without hyperons, and calculate the structure evolution in full general relativity. We assess the binary parameters leading either NS in the binary to the critical mass for gravitational collapse into a BH and its occurrence time, tcol. We include a nonzero angular momentum of the NSs and find that tcol ranges from a few tens of seconds to hours for decreasing NS initial angular momentum values. BdHNe I are the most compact (about 5 minute orbital period), promptly form a BH, and release ≳1052 erg of energy. They form NS–BH binaries with tens of kiloyears merger timescales by gravitational-wave emission. BdHNe II and III do not form BHs, and release ∼1050–1052 erg and ≲1050 erg of energy, respectively. They form NS–NS binaries with a range of merger timescales larger than for NS–BH binaries. In some compact BdHNe II, either NS can become supramassive, i.e., above the critical mass of a nonrotating NS. Magnetic braking by a 1013 G field can delay BH formation, leading to BH–BH or NS–BH with tens of kiloyears merger timescales.
Orlando Luongoand Marco Muccino, Model-independent cosmographic constraints from DESI 2024, published in Astronomy & Astrophysics, Volume 690, on October 2024.
Context. We explore model-independent constraints on the Universe kinematics up to the snap and jerk hierarchical terms, considering the latest baryon acoustic oscillation (BAO) release provided by the DESI collaboration.
Aims. We intend to place novel and more stringent constraints on the cosmographic series, incorporating three combinations of data catalogs: the first made by BAO and observational cosmic chronometers, the second made by BAO and type Ia supernovae, and the last including all the cited data sets.
Methods. Considering the latest BAO data provided by the DESI collaboration and tackling the rd parameter to span within the range [144,152] Mpc, with a fixed step of δrd = 2 Mpc, we employed Monte Carlo Markov chain analyses based on the Metropolis algorithm to fix novel bounds on the cosmographic series, fixing the deceleration, q0, the jerk, j0, and the snap, s0, parameters, up to the 2σ level. A comparison between the results of the Planck satellite with those obtained by the DESI collaboration is also reported.
Results. Our findings showcase a significant departure in terms of j0 even at the 1σ confidence level, albeit compatible with the ACDM paradigm in regard to q0 and s0 at the 2σ level. Analogously, the h0 tension appears alleviated in the second hierarchy when including snap.
Conclusions. Our method excludes models that significantly depart from the standard cosmological model. Particularly, direct comparisons with the ACDM and wCDM models and the Chevallier-Polarski-Linder parameterisation are explored, which definitively favour the wCDM scenario over other approaches, contradicting the findings of the original DESI collaboration.
Wang, Yu; Moradi, Rahim; Li, Liang, Multipolar Electromagnetic Emission of Newborn Magnetars, published in The Astrophysical Journal, Volume 974, Number 1 on October 7, 2024.
It is generally recognized that the electromagnetic multipolar emission from magnetars can be used to explain radiation from soft gamma repeaters or anomalous X-ray pulsars, but they have little impact on the spin-down of magnetars. We here present an analytical solution for the neutron star multipolar electromagnetic fields and their associated expected luminosities. We find that for newborn millisecond magnetars, the spin-down luminosity from higher multipolar components can match or even exceed that from the dipole component. Such high-intensity radiation will undoubtedly affect related astrophysical phenomena at the birth of a magnetar. We show that the spin-down luminosity from multipoles can well explain the majority of gamma-ray burst (GRB) afterglows, from the plateau starting at several hundred seconds until the normal decay phase lasting for many years. The fitted magnetar parameters for GRB afterglows are all typical values, with spins in the millisecond range and magnetic field strengths on the order of 1014–1015 G. Our results, in turn, provide support for the hypothesis that GRBs originate from the birth of magnetars with a period of a few milliseconds, thus deepening our understanding of the complex magnetic field structure and the equation of state of magnetars.
J Pelle, C R Argüelles, F L Vieyro, V Crespi, C Millauro, M F Mestre, O Reula, F Carrasco, Imaging fermionic dark matter cores at the centre of galaxies, published in Monthly Notices of the Royal Astronomical Society, Volume 534, Issue 2 on October 2024.
Current images of the supermassive black hole (SMBH) candidates at the centre of our Galaxy and M87 have opened an unprecedented era for studying strong gravity and the nature of relativistic sources. Very-long-baseline interferometry data show images consistent with a central SMBH within General Relativity (GR). However, it is essential to consider whether other well-motivated dark compact objects within GR could produce similar images. Recent studies have shown that dark matter (DM) haloes modelled as self-gravitating systems of neutral fermions can harbour very dense fermionic cores at their centres, which can mimic the space-time features of a black hole (BH). Such dense, horizonless DM cores can satisfy the observational constraints: they can be supermassive and compact and lack a hard surface. We investigate whether such cores can produce similar observational signatures to those of BHs when illuminated by an accretion disc. We compute images and spectra of the fermion cores with a general-relativistic ray tracing technique, assuming the radiation originates from standard αdiscs, which are self-consistently solved within the current DM framework. Our simulated images possess a central brightness depression surrounded by a ring-like feature, resembling what is expected in the BH scenario. For Milky Way-like haloes, the central brightness depressions have diameters down to ∼35μasas measured from a distance of approximately 8 kpc. Finally, we show that the DM cores do not possess photon rings, a key difference from the BH paradigm, which could help discriminate between the models.
MAGIC collaboration, Constraints on VHE gamma-ray emission of flat spectrum radio quasars with the MAGIC telescopes, published in Monthly Notices of the Royal Astronomical Society, Volume 535, Issue 2 on October 8, 2024.
Flat spectrum radio quasars (FSRQs) constitute a class of jetted active galaxies characterized by a very luminous accretion disc, prominent and rapidly moving line-emitting cloud structures (broad-line region, BLR), and a surrounding dense dust structure known as dusty torus. The intense radiation field of the accretion disc strongly determines the observational properties of FSRQs. While hundreds of such sources have been detected at GeV energies, only a handful of them exhibit emission in the very-high-energy (VHE, E ≥ 100 GeV) range. This study presents the results and interpretation derived from a cumulative observation period of 174 h dedicated to nine FSRQs conducted with the Major Atmospheric Gamma-ray Imaging Cherenkov telescopes from 2008 to 2020. Our findings indicate no statistically significant (≥5σ) signal for any of the studied sources, resulting in upper limits on the emission within the VHE energy range. In two of the sources, we derived quite stringent constraints on the gamma-ray emission in the form of upper limits. Our analysis focuses on modelling the VHE emission of these two sources in search for hints of absorption signatures within the BLR radiation field. For these particular sources, constraints on the distance between the emission region and the central black hole are derived using a phenomenological model. Subsequently, these constraints are tested using a framework based on a leptonic model.
MAGIC collaboration, Standardised formats and open-source analysis tools for the MAGIC telescopes data, published in Journal of High Energy Astrophysics, Volume 44 on November 2024.
Instruments for gamma-ray astronomy at Very High Energies (E 100 GeV) have traditionally derived their scientific results through proprietary data and software. Data standardisation has become a prominent issue in this field both as a requirement for the dissemination of data from the next generation of gamma-ray observatories and as an effective solution to realise public data legacies of current-generation instruments. Specifications for a standardised gamma-ray data format have been proposed as a community effort and have already been successfully adopted by several instruments. We present the first production of standardised data from the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes. We converted 166 h of observations from different sources and validated their analysis with the open-source software Gammapy. We consider six data sets representing different scientific and technical analysis cases and compare the results obtained analysing the standardised data with open-source software against those produced with the MAGIC proprietary data and software. Aiming at a systematic production of MAGIC data in this standardised format, we also present the implementation of a database-driven pipeline automatically performing the MAGIC data reduction from the calibrated down to the standardised data level. In all the cases selected for the validation, we obtain results compatible with the MAGIC proprietary software, both for the manual and for the automatic data productions. Part of the validation data set is also made publicly available, thus representing the first large public release of MAGIC data. This effort and this first data release represent a technical milestone toward the realisation of a public MAGIC data legacy.
Martínez, Jhan N.; Rodríguez, José F.; Becerra, Laura M.; Rodríguez, Yeinzon; Gómez, Gabriel, Neutron stars in the generalized SU(2) Proca theory, published in Physical Review D, Volume 110, Issue 10 on November 2024.
The generalized SU(2) Proca theory is a vector-tensor modified gravity theory characterized by an action that remains invariant under both diffeomorphisms and global internal transformations of the SU(2) group. This study aims to further explore the physical properties of the theory within astrophysical contexts. Previous investigations have unveiled intriguing astrophysical solutions, including particlelike configurations and black holes. The purpose of this work is to constrain the theory's free parameters by modeling realistic neutron stars. To that end, we have assumed solutions that are static, spherically symmetric, and have adopted the 't Hooft-Polyakov magnetic monopole configuration for the vector fields. Employing both analytical techniques, such as asymptotic expansions, and numerical methods involving solving boundary value problems, we have obtained neutron star solutions whose baryonic matter is described by realistic equations of state for nuclear matter. Furthermore, we have constructed mass-radius relations which reveal that neutron stars exhibit greater compactness in comparison with general relativity predictions for most of the solutions we have found and for the employed equations of state. Finally, we have found out solutions where the mass of the star is greater than ∼2.5M⊙; this result poses an alternative in the exploration of the mass gap of compact stellar objects.
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