ICRANet Newsletter
ICRANet Newsletter
February – March 2025
February – March 2025
SUMMARY
1. Scientific highlights: ICRANet papers published in PRL and PRR
2. ICRA – ICRANet press release “New Research Unveils the Role of Irreducible Mass in Energy Extraction from Kerr Black Holes”, March 13, 2025
3. ICRA – ICRANet press release “New Study Sheds Light on the Penrose Process and Energy Extraction from Kerr Black Holes”, March 13, 2025
4. ICRANet GCN
5.ICRANet participation at the “Planetarium day 2025”, March 23, 2025, Ortona (Italy)
6.Stellæ Laetatae Sunt. Exhibition “The meridian ellipses of the Jubilees”, from March 20, 2025, Cathedral S. Maria degli Angeli e dei Martiri, Rome (Italy)
7.Partial Solar Eclipse. Measure of the Solar Diameter during Solar Maximum, March 29, 2025
8. New cooperation agreement between ICRANet and University of Tartu (UT), November 30, 2024
9. New cooperation agreement between ICRANet and Univesidad Mayor, December 10, 2024
10.New cooperation agreement between ICRANet and the Catholic Institute of Technology (CatholicTech), February 4, 2025
11. Renewal of the cooperation agreement between ICRANet and Universidad Industrial de Santander, December 2, 2024
12.Renewal of the cooperation agreement between ICRANet and Universidad Del Valle, March 21, 2025
13. Renewal of the cooperation agreement between ICRANet and the LEPL-IvaneJavakhishvili Tbilisi State University (TSU), February 6, 2025
14.Scientific visits to ICRANet
15.Recent publications
1. Scientific highlights: ICRANet papers published in PRL and PRR
2. ICRA – ICRANet press release “New Research Unveils the Role of Irreducible Mass in Energy Extraction from Kerr Black Holes”, March 13, 2025
3. ICRA – ICRANet press release “New Study Sheds Light on the Penrose Process and Energy Extraction from Kerr Black Holes”, March 13, 2025
4. ICRANet GCN
5.ICRANet participation at the “Planetarium day 2025”, March 23, 2025, Ortona (Italy)
6.Stellæ Laetatae Sunt. Exhibition “The meridian ellipses of the Jubilees”, from March 20, 2025, Cathedral S. Maria degli Angeli e dei Martiri, Rome (Italy)
7.Partial Solar Eclipse. Measure of the Solar Diameter during Solar Maximum, March 29, 2025
8. New cooperation agreement between ICRANet and University of Tartu (UT), November 30, 2024
9. New cooperation agreement between ICRANet and Univesidad Mayor, December 10, 2024
10.New cooperation agreement between ICRANet and the Catholic Institute of Technology (CatholicTech), February 4, 2025
11. Renewal of the cooperation agreement between ICRANet and Universidad Industrial de Santander, December 2, 2024
12.Renewal of the cooperation agreement between ICRANet and Universidad Del Valle, March 21, 2025
13. Renewal of the cooperation agreement between ICRANet and the LEPL-IvaneJavakhishvili Tbilisi State University (TSU), February 6, 2025
14.Scientific visits to ICRANet
15.Recent publications
1.Scientific highlights: ICRANet papers published in PRL and PRR
Remo Ruffini, MikalaiPrakapenia, Hernando Quevedo, and Shurui Zhang, Single versus the Repetitive Penrose Process in a Kerr Black Hole, Phys.
Extracting the rotational energy from a Kerr black hole (BH) is one of the crucial topics in relativistic astrophysics. Here, we give special attention to the Penrose ballistic process based on the fission of a massive particle 𝜇0 into two particles 𝜇1 and 𝜇2, occurring in the ergosphere of a Kerr BH. Bardeen et al. indicated that for the process to occur, some additional “hydrodynamical forces or superstrong radiation reactions” were needed. Wald and Chandrasekhar further expanded this idea. This animosity convinced Piran and collaborators to move from a simple three-body system characterizing the original Penrose process to a many-body system. This many-body approach was further largely expanded by others, some questionable in their validity. Here, we return to the simplest original Penrose process and show that the solution of the equations of motion, imposing the turning point condition on their trajectories, leads to the rotational energy extraction from the BH expected by Penrose. The efficiency of energy extraction by a single process is quantified for three different single decay processes occurring, respectively, at 𝑟 =1.2𝑀, 𝑟 =1.5𝑀, and 𝑟 =1.9𝑀. An interesting repetitive model has been proposed by Misner et al. [Gravitation (W. H. Freeman, San Francisco, 1973)]. Indeed, it would appear that a repetitive sequence of 246 decays of the above injection process at 𝑟 =1.2𝑀 and the corresponding ones at 𝑟 =1.5𝑀 and 𝑟 =1.9𝑀 could extract 100% of the rotational energy of the BH, so violating energy conservation. The accompanying article, accounting for the existence of the BH irreducible mass, introduces a nonlinear approach that avoids violating energy conservation and leads to a new energy extraction process.
DOI: https://doi.org/10.1103/PhysRevLett.134.081403
R. Ruffini, C. L. Bianco, M. Prakapenia, H. Quevedo, J. A. Rueda, and S. Zhang, Role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole, Phys. Rev. Research 7, 013203 (2025).
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 nonrotating 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.
DOI:https://doi.org/10.1103/PhysRevResearch.7.013203
Extracting the rotational energy from a Kerr black hole (BH) is one of the crucial topics in relativistic astrophysics. Here, we give special attention to the Penrose ballistic process based on the fission of a massive particle 𝜇0 into two particles 𝜇1 and 𝜇2, occurring in the ergosphere of a Kerr BH. Bardeen et al. indicated that for the process to occur, some additional “hydrodynamical forces or superstrong radiation reactions” were needed. Wald and Chandrasekhar further expanded this idea. This animosity convinced Piran and collaborators to move from a simple three-body system characterizing the original Penrose process to a many-body system. This many-body approach was further largely expanded by others, some questionable in their validity. Here, we return to the simplest original Penrose process and show that the solution of the equations of motion, imposing the turning point condition on their trajectories, leads to the rotational energy extraction from the BH expected by Penrose. The efficiency of energy extraction by a single process is quantified for three different single decay processes occurring, respectively, at 𝑟 =1.2𝑀, 𝑟 =1.5𝑀, and 𝑟 =1.9𝑀. An interesting repetitive model has been proposed by Misner et al. [Gravitation (W. H. Freeman, San Francisco, 1973)]. Indeed, it would appear that a repetitive sequence of 246 decays of the above injection process at 𝑟 =1.2𝑀 and the corresponding ones at 𝑟 =1.5𝑀 and 𝑟 =1.9𝑀 could extract 100% of the rotational energy of the BH, so violating energy conservation. The accompanying article, accounting for the existence of the BH irreducible mass, introduces a nonlinear approach that avoids violating energy conservation and leads to a new energy extraction process.
DOI: https://doi.org/10.1103/PhysRevLett.134.081403
R. Ruffini, C. L. Bianco, M. Prakapenia, H. Quevedo, J. A. Rueda, and S. Zhang, Role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole, Phys. Rev. Research 7, 013203 (2025).
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 nonrotating 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.
DOI:https://doi.org/10.1103/PhysRevResearch.7.013203
2.ICRA – ICRANet press release “New Research Unveils the Role of Irreducible Mass in Energy Extraction from Kerr Black Holes”, March 13, 2025
Pescara, Italy – March 13.03.2025
A new study published in Physical Review Research offers a major breakthrough in our understanding of the Penrose process, refining our knowledge of energy extraction from Kerr black holes. Building on a previous study in Physical Review Letters, this work clarifies the limitations of the repetitive Penrose process and establishes the central role of irreducible mass in black hole dynamics. The study, titled “Role of the Irreducible Mass in Repetitive Penrose Energy Extraction Processes in a Kerr Black Hole,” highlights the highly nonlinear nature of energy extraction from a rotating black hole. The research team, led by scientists from ICRANet and global institutions, demonstrates that the increase in a black hole’s irreducible mass significantly limits the efficiency of repetitive Penrose processes, debunking prior assumptions about the feasibility of extracting the entirety of a black hole’s rotational energy.
“Our findings show that, contrary to previous expectations, the Penrose process is far from a linear, scale-invariant mechanism,” said Professor Remo Ruffini, one of the study’s lead authors. “Instead, the irreducible mass increases much more than the extracted energy, ultimately halting the process after a finite number of iterations.”
Key results of the study include:
Nonlinear limitations: The research demonstrates that each successive decay event in the ergosphere of a Kerr black hole leads to an increase in irreducible mass, which quickly outweighs the extracted energy.
Finite energy extraction: The iterative Penrose process stops well before a black hole can be fully stripped of its rotational energy. The latter amounts to a maximum of 29% of the black hole mass if it is at maximal rotation. For selected decay radii inside the black hole’s ergosphere and a decaying particle mass of 1% of the mass of a maximally rotating black hole, the paper shows that energy extraction ceases after as few as 8 or as many as 34 iterations, extracting at most 1% and 0.4% of the black hole’s mass, while reducing the rotational energy by 17% and 50%. Breakdown of naive repetition models: The above implies that the work corrects prior assumptions that a sufficiently large number of iterations could extract 100% of a black hole’s rotational energy. Instead, the process is self-limiting, as rotational energy in the process is primarily converted into black hole’s irreducible mass rather than released to infinity.
An animation showing an example of repetitive Penrose process in a maximally rotating black hole examined in the paper, can be found in the videosof the repetitive Penrose process:
http://www.icranet.org/documents/video_dot1.mp4
http://www.icranet.org/documents/video_dot2.mp4
http://www.icranet.org/documents/video_dot3.mp4
These findings have profound implications for astrophysical models involving black hole energy extraction well identified in gamma-ray bursts GRB's and other high-energy cosmic events. This study serves as a complementary extension to the team’s previous work, “Single versus the Repetitive Penrose Process in a Kerr Black Hole”, published in Physical Review Letters. Together, these studies provide a comprehensive revision of the Penrose process and its constraints, implying the need for alternative processes to extract the black hole’s energy keeping the irreducible mass increase as small as possible. In this line, electro dynamical processes appear as a promising path as shown by recent works of the team.
The publication of the original results goes back fifty years and has been followed for many decades of thinking and progress reaching the final form in these days: it is fortunate that the main contributors : Roger Penrose and Remo Ruffini) have enjoyed sharing and discussing these results and indicate further developments (see Enclosure 1 "Roger Penrose to Remo Ruffini, February 23, 2025" and Enclosure 2 "Remo Ruffini to Roger Penrose, February 26, 2025"). An essential point to address is the objective scientific urgency of addressing these results: since the first discovery of a BH in Cygnus X1 in a binary X-ray source (Ruffini , N.Y. Texas Meeting 1972), the largest observational effort in developing observatories from the ground and from space have reached the scope: "Identify BHs all over the Universe" : from inside our galaxy to extragalactic sources all the way to the highest cosmological redshift at Z= 10 and higher prior to the decoupling era. The BHs, typically of 2-10 Solar Masses, originate from the collapse of "baryonic matter". The great novelty is the current discovery of BHs much larger masses, at 4.6 106 all the way to 1010 solar masses originating from Dark Matter and manifesting themselves from cosmological Z=10 in supermassive BHs, all the way to Z=2 under the form of Quasars.
Precisely this topic has been indicated as a high priority in the Penrose-Ruffini exchange. Progress has been made daily in ICRANetby Arguelles, Rueda , Ruffini (January 11, 2024); Ruffini -Vereshchagin March 2025, and Ruffini, Della Valle - Wang Yu (March 2025). They examine BH composed of both Dark Matter and Baryonic matter and determine their evolution. Of great relevance for this new paradigm are the observations of the Red-Dots by the James Webb Space Telescope of NASA: “Red-Dots messenger of CDMB, a Cosmic Dark-Matter Background” coeval to the better known “CMB Cosmic Microwave Background”.
The paper published in Physical Review Research can be accessed here:
https://doi.org/10.1103/PhysRevResearch.7.013203
The accompanying paper published in Physical Review Letters can be accessed here:
https://doi.org/10.1103/PhysRevLett.134.081403
About the Research Team This study was conducted by researchers from ICRANet, ICRA, INAF, University of Ferrara, University of Science and Technology of China, the Universidad Nacional Autónoma de México, Al-Farabi Kazakh National University. Their work advances our theoretical understanding of black hole energetics, merging general relativity with high-energy astrophysics.
For the press release on ICRANet website, both in English and Chinese:
https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
A new study published in Physical Review Research offers a major breakthrough in our understanding of the Penrose process, refining our knowledge of energy extraction from Kerr black holes. Building on a previous study in Physical Review Letters, this work clarifies the limitations of the repetitive Penrose process and establishes the central role of irreducible mass in black hole dynamics. The study, titled “Role of the Irreducible Mass in Repetitive Penrose Energy Extraction Processes in a Kerr Black Hole,” highlights the highly nonlinear nature of energy extraction from a rotating black hole. The research team, led by scientists from ICRANet and global institutions, demonstrates that the increase in a black hole’s irreducible mass significantly limits the efficiency of repetitive Penrose processes, debunking prior assumptions about the feasibility of extracting the entirety of a black hole’s rotational energy.
“Our findings show that, contrary to previous expectations, the Penrose process is far from a linear, scale-invariant mechanism,” said Professor Remo Ruffini, one of the study’s lead authors. “Instead, the irreducible mass increases much more than the extracted energy, ultimately halting the process after a finite number of iterations.”
Key results of the study include:
Nonlinear limitations: The research demonstrates that each successive decay event in the ergosphere of a Kerr black hole leads to an increase in irreducible mass, which quickly outweighs the extracted energy.
Finite energy extraction: The iterative Penrose process stops well before a black hole can be fully stripped of its rotational energy. The latter amounts to a maximum of 29% of the black hole mass if it is at maximal rotation. For selected decay radii inside the black hole’s ergosphere and a decaying particle mass of 1% of the mass of a maximally rotating black hole, the paper shows that energy extraction ceases after as few as 8 or as many as 34 iterations, extracting at most 1% and 0.4% of the black hole’s mass, while reducing the rotational energy by 17% and 50%. Breakdown of naive repetition models: The above implies that the work corrects prior assumptions that a sufficiently large number of iterations could extract 100% of a black hole’s rotational energy. Instead, the process is self-limiting, as rotational energy in the process is primarily converted into black hole’s irreducible mass rather than released to infinity.
An animation showing an example of repetitive Penrose process in a maximally rotating black hole examined in the paper, can be found in the videosof the repetitive Penrose process:
http://www.icranet.org/documents/video_dot1.mp4
http://www.icranet.org/documents/video_dot2.mp4
http://www.icranet.org/documents/video_dot3.mp4
These findings have profound implications for astrophysical models involving black hole energy extraction well identified in gamma-ray bursts GRB's and other high-energy cosmic events. This study serves as a complementary extension to the team’s previous work, “Single versus the Repetitive Penrose Process in a Kerr Black Hole”, published in Physical Review Letters. Together, these studies provide a comprehensive revision of the Penrose process and its constraints, implying the need for alternative processes to extract the black hole’s energy keeping the irreducible mass increase as small as possible. In this line, electro dynamical processes appear as a promising path as shown by recent works of the team.
The publication of the original results goes back fifty years and has been followed for many decades of thinking and progress reaching the final form in these days: it is fortunate that the main contributors : Roger Penrose and Remo Ruffini) have enjoyed sharing and discussing these results and indicate further developments (see Enclosure 1 "Roger Penrose to Remo Ruffini, February 23, 2025" and Enclosure 2 "Remo Ruffini to Roger Penrose, February 26, 2025"). An essential point to address is the objective scientific urgency of addressing these results: since the first discovery of a BH in Cygnus X1 in a binary X-ray source (Ruffini , N.Y. Texas Meeting 1972), the largest observational effort in developing observatories from the ground and from space have reached the scope: "Identify BHs all over the Universe" : from inside our galaxy to extragalactic sources all the way to the highest cosmological redshift at Z= 10 and higher prior to the decoupling era. The BHs, typically of 2-10 Solar Masses, originate from the collapse of "baryonic matter". The great novelty is the current discovery of BHs much larger masses, at 4.6 106 all the way to 1010 solar masses originating from Dark Matter and manifesting themselves from cosmological Z=10 in supermassive BHs, all the way to Z=2 under the form of Quasars.
Precisely this topic has been indicated as a high priority in the Penrose-Ruffini exchange. Progress has been made daily in ICRANetby Arguelles, Rueda , Ruffini (January 11, 2024); Ruffini -Vereshchagin March 2025, and Ruffini, Della Valle - Wang Yu (March 2025). They examine BH composed of both Dark Matter and Baryonic matter and determine their evolution. Of great relevance for this new paradigm are the observations of the Red-Dots by the James Webb Space Telescope of NASA: “Red-Dots messenger of CDMB, a Cosmic Dark-Matter Background” coeval to the better known “CMB Cosmic Microwave Background”.
The paper published in Physical Review Research can be accessed here:
https://doi.org/10.1103/PhysRevResearch.7.013203
The accompanying paper published in Physical Review Letters can be accessed here:
https://doi.org/10.1103/PhysRevLett.134.081403
About the Research Team This study was conducted by researchers from ICRANet, ICRA, INAF, University of Ferrara, University of Science and Technology of China, the Universidad Nacional Autónoma de México, Al-Farabi Kazakh National University. Their work advances our theoretical understanding of black hole energetics, merging general relativity with high-energy astrophysics.
For the press release on ICRANet website, both in English and Chinese:
https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
3.ICRA – ICRANet press release “New Study Sheds Light on the Penrose Process and Energy Extraction from Kerr Black Holes”, March 13, 2025
Pescara, Italy – March 13, 2025
A groundbreaking study published in Physical Review Letters explores the long-debated Penrose process, shedding new light on the extraction of rotational energy from Kerr black holes. Led by a team of international researchers from ICRANet and other global institutions, the study provides novel insights into the fundamental physics of energy extraction of astrophysical black holes. The research, titled “Single versus the Repetitive Penrose Process in a Kerr Black Hole,” revisits the original Penrose process, a theoretical model proposed by Roger Penrose in 1969. The study examines how a single decay event of a massive particle into two particles inside the ergosphere of a rotating black hole can result in energy extraction. The team successfully demonstrated that, contrary to earlier criticisms, the single-event Penrose process is indeed capable of extracting significant energy efficiently, with an upper efficiency of 14.5% for a maximally rotating Kerr black hole.
A key aspect of the study also explores the possibility of a repetitive Penrose process, first suggested by Misner, Thorne, and Wheeler in Gravitation (1973). The researchers theoretically analyzed an iterative sequence of decay processes, which, if naively implemented, would appear to extract 100% of the rotational energy of a black hole. However, their findings highlight a crucial limitation: such a linear repetitive process would violate energy conservation laws. The team highlights that this inconsistency can be solved by properly incorporating the nonlinearity introduced by the increase of the irreducible mass of the black hole during the process, which is the subject of an accompanying publication in Physical Review Research. These results laid the groundwork for a revised energy extraction mechanism that obeys fundamental conservation principles.
“Our study clarifies the feasibility of the Penrose process as a mechanism for energy extraction from Kerr black holes,” said Professor Remo Ruffini, first author of the paper. “We have demonstrated that a single Penrose process is indeed effective, no modifications are needed as previously assumed. The authors have also uncovered the key limitations of a naive repetitive approach and, in the specific examples provided, evidenced significant mass defect constraints. This research provides a necessary step toward a more complete understanding of black hole energetics.”
These findings have broad implications for astrophysics, including the study of high-energy cosmic phenomena such as gamma-ray bursts and active galactic nuclei, where black hole rotational energy may play a critical role. Future research will aim to expand on these results, further refining our understanding of black hole dynamics and potential astrophysical applications. The paper published in Physical Review Letters can be accessed here:
https://doi.org/10.1103/PhysRevLett.134.081403
The accompanying paper published in Physical Review Research can be accessed here:
https://doi.org/10.1103/PhysRevResearch.7.013203
About the Research Team This study was conducted by researchers from ICRANet, ICRA, INAF, Al-Farab Kazakh National University, the University of Science and Technology of China, the Universidad Nacional Autónoma de México, and other institutions. Their work builds on decades of theoretical advancements in black hole physics, combining classical general relativity with modern astrophysical insights.
For the press release on ICRANet website, both in English and Chinese:
https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
A groundbreaking study published in Physical Review Letters explores the long-debated Penrose process, shedding new light on the extraction of rotational energy from Kerr black holes. Led by a team of international researchers from ICRANet and other global institutions, the study provides novel insights into the fundamental physics of energy extraction of astrophysical black holes. The research, titled “Single versus the Repetitive Penrose Process in a Kerr Black Hole,” revisits the original Penrose process, a theoretical model proposed by Roger Penrose in 1969. The study examines how a single decay event of a massive particle into two particles inside the ergosphere of a rotating black hole can result in energy extraction. The team successfully demonstrated that, contrary to earlier criticisms, the single-event Penrose process is indeed capable of extracting significant energy efficiently, with an upper efficiency of 14.5% for a maximally rotating Kerr black hole.
A key aspect of the study also explores the possibility of a repetitive Penrose process, first suggested by Misner, Thorne, and Wheeler in Gravitation (1973). The researchers theoretically analyzed an iterative sequence of decay processes, which, if naively implemented, would appear to extract 100% of the rotational energy of a black hole. However, their findings highlight a crucial limitation: such a linear repetitive process would violate energy conservation laws. The team highlights that this inconsistency can be solved by properly incorporating the nonlinearity introduced by the increase of the irreducible mass of the black hole during the process, which is the subject of an accompanying publication in Physical Review Research. These results laid the groundwork for a revised energy extraction mechanism that obeys fundamental conservation principles.
“Our study clarifies the feasibility of the Penrose process as a mechanism for energy extraction from Kerr black holes,” said Professor Remo Ruffini, first author of the paper. “We have demonstrated that a single Penrose process is indeed effective, no modifications are needed as previously assumed. The authors have also uncovered the key limitations of a naive repetitive approach and, in the specific examples provided, evidenced significant mass defect constraints. This research provides a necessary step toward a more complete understanding of black hole energetics.”
These findings have broad implications for astrophysics, including the study of high-energy cosmic phenomena such as gamma-ray bursts and active galactic nuclei, where black hole rotational energy may play a critical role. Future research will aim to expand on these results, further refining our understanding of black hole dynamics and potential astrophysical applications. The paper published in Physical Review Letters can be accessed here:
https://doi.org/10.1103/PhysRevLett.134.081403
The accompanying paper published in Physical Review Research can be accessed here:
https://doi.org/10.1103/PhysRevResearch.7.013203
About the Research Team This study was conducted by researchers from ICRANet, ICRA, INAF, Al-Farab Kazakh National University, the University of Science and Technology of China, the Universidad Nacional Autónoma de México, and other institutions. Their work builds on decades of theoretical advancements in black hole physics, combining classical general relativity with modern astrophysical insights.
For the press release on ICRANet website, both in English and Chinese:
https://www.icranet.org/index.php?option=com_content&task=view&id=1032&Itemid=920
4.ICRANet GCN
TITLE: GCN CIRCULAR
NUMBER: 39366
SUBJECT: GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
DATE: 25/02/18 17:28:03 GMT
FROM: Remo Ruffini at ICRA ruffini@icra.it
R. Ruffini, D. Berkimbayev, G. Vereshchagin, R. F. Mohideen Malik, N. Shynggyskhan, M.T. Mirtorabi, J.A. Rueda, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:
GRB 250215A / EP250215A was detected by Fermi (GCN 39327), Einstein Probe (GCN 39329), and SVOM (GCN 39333) at a redshift of z = 4.61 (GCN 39343). The burst duration is 2.3 s in the rest frame, corresponding to T_{90} = 13.4 s in the observer's frame (GCN 39342). The isotropic energy release is 3 \times 10^{53} erg, consistent with a BdHN I classification. This event shares similarities with GRB 220101A (GCN 37964), GRB 221009A (GCN 32828), and GRB 240825A (GCN 37536). Extended follow-up multi-wavelength observations are encouraged to fully characterize the BdHN I episodes: optical data for pulsar identification, X-ray observations to track the afterglow evolution, and GeV measurements to constrain the black hole energy.
NUMBER: 39366
SUBJECT: GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
DATE: 25/02/18 17:28:03 GMT
FROM: Remo Ruffini at ICRA ruffini@icra.it
R. Ruffini, D. Berkimbayev, G. Vereshchagin, R. F. Mohideen Malik, N. Shynggyskhan, M.T. Mirtorabi, J.A. Rueda, Y. Wang, S.S. Xue, on behalf of the ICRANet team, report:
GRB 250215A / EP250215A was detected by Fermi (GCN 39327), Einstein Probe (GCN 39329), and SVOM (GCN 39333) at a redshift of z = 4.61 (GCN 39343). The burst duration is 2.3 s in the rest frame, corresponding to T_{90} = 13.4 s in the observer's frame (GCN 39342). The isotropic energy release is 3 \times 10^{53} erg, consistent with a BdHN I classification. This event shares similarities with GRB 220101A (GCN 37964), GRB 221009A (GCN 32828), and GRB 240825A (GCN 37536). Extended follow-up multi-wavelength observations are encouraged to fully characterize the BdHN I episodes: optical data for pulsar identification, X-ray observations to track the afterglow evolution, and GeV measurements to constrain the black hole energy.
5.ICRANet participation at the “Planetarium day 2025”, March 23, 2025, Ortona (Italy)
In the afternoon, he met Prof. Pietro Di Pasquale, who informed him about the progresses of the meteorology laboratory, from which they daily follow the launches of the air force’s METAR sounding balloons. They also compared methods and data for weather station calibration, as well as their inclusion in the Italian network with which Prof. Sigismondi collaborates since 2017 with the rainfall data from Rome. The afternoon program went on with a lecture by Dr. Antonio Ricchi (University of L'Aquila) on meteorology and artificial intelligence. Prof. Sigismondi exchanged with him some ideason the weather data of the October 2023 annular eclipse, thatDrRicchi measured in Ohio.
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.
For the website of the meeting: https://www.iisacciaiuolieinaudi.it/xxxv-giornata-dei-planetari/
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On Sunday March 23, 2025, Prof. Costantino Sigismondi, ICRANet Adjunct Professor, has been invited to present a lecture on the occasion of the “Planetarium day 2025”, organized by the Nautical High School IIS Acciaiuoli – Einaudi of Ortona (Abruzzo, Italy). Prof. Sigismondi presented a lecture titled “Solar maximum, eclipse and Maunder minimum”.
After the conference, Prof. Sigismondi visited the School and its telescopes and discussed with the Dean of the School, Prof. Angela Potenza, as well as with the teachers about the observation of the upcoming solar eclipse and the concluding phases of the solar maximum. |
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.
For the website of the meeting: https://www.iisacciaiuolieinaudi.it/xxxv-giornata-dei-planetari/
6.Stellæ Laetatæ Sunt. Exhibition “The meridian ellipses of the Jubilees”, from March 20, 2025, Cathedral S. Maria degli Angeli e dei Martiri, Rome (Italy)
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| Fig. 1: Pope Benedict XVI visiting the Basilica of St. Maria degli Angeli e dei Martiri on the Meridian Line (April 11, 2011). | |
The ellipses of the Polaris, calculated for the series of the Jubilee years, starting from 1700 to 2500, are a unique masterpiece of science, history and art. The baricenter of the ellipses is the Celestial North Pole, and its altitude above the Northern horizon is the local latitude.
This exhibition has been prepared for the 2025 Jubilee and has been opened from March 20, 2025, thanks to the precious help of prof. Costantino Sigismondi (ICRANet adjunct Professor).In parallel are shown the stages of the History of Astronomy in Rome.
The website of the event:https://www.icranet.org/index.php?option=com_content&task=view&id=1573
The website of the event:https://www.icranet.org/index.php?option=com_content&task=view&id=1573
7.Partial Solar Eclipse. Measure of the Solar Diameter during Solar Maximum, March 29, 2025
Measuring the solar diameter during total eclipses is favored by the "on-off" signal of the Baily's beads formed by the lunar valleys on the solar limbs' photosphere.
During partial eclipses it is more difficult: the lunar profile's contacts timing are obtained from extrapolating video images of the first and last "bites" of Moon at the solar limb. The ability of skilled solar observers united with the UTC synchronized timing familiarity -especially by the IOTA fellows- can permit to get useful data.
This eclipse will be compared with 2006 total one, and it occurs after a Methon cycle of 19 years with interesting proprties of "conservation" of the lunar limbs profiles (the lunar nodes revolve in 18.6 years and the saros is 18.03 years). The solar activity can also influence the solar diameter, as envisaged by Secchi and Rosa at Collegio Romano in XIX century, for details see:https://www.worldscientific.com/doi/10.1142/9789811258251_0266?srsltid=AfmBOoow8RVrOsEty93i0DcuAPWeVAWyTwZ-sikkmlBVL1c6NDPh6rr5 From March 28 to April 1, 2025 Prof. Sigismondi visited the IRSOL (Istituto RicercheSolari Observatory) in Locarno to use the largest solar telescope on European soil, in order to measure the diameter of the Sun with the eclipse. He has been in this Swiss centre of excellence and acquired numerous images of the event, as reported in the news of the University of Italian Switzerland to which IRSOL belongs and to which he contributed with the high-resolution H-alpha image of the eclipsed Sun.
On the same day of the eclipse, March 29, Prof. Sigismondi participated in the Ticino Astronomical Society's conference describing the importance of observing the partial eclipse. Also fruitful has been the visit to the Specola Solare Ticinese.
During partial eclipses it is more difficult: the lunar profile's contacts timing are obtained from extrapolating video images of the first and last "bites" of Moon at the solar limb. The ability of skilled solar observers united with the UTC synchronized timing familiarity -especially by the IOTA fellows- can permit to get useful data.
This eclipse will be compared with 2006 total one, and it occurs after a Methon cycle of 19 years with interesting proprties of "conservation" of the lunar limbs profiles (the lunar nodes revolve in 18.6 years and the saros is 18.03 years). The solar activity can also influence the solar diameter, as envisaged by Secchi and Rosa at Collegio Romano in XIX century, for details see:https://www.worldscientific.com/doi/10.1142/9789811258251_0266?srsltid=AfmBOoow8RVrOsEty93i0DcuAPWeVAWyTwZ-sikkmlBVL1c6NDPh6rr5 From March 28 to April 1, 2025 Prof. Sigismondi visited the IRSOL (Istituto RicercheSolari Observatory) in Locarno to use the largest solar telescope on European soil, in order to measure the diameter of the Sun with the eclipse. He has been in this Swiss centre of excellence and acquired numerous images of the event, as reported in the news of the University of Italian Switzerland to which IRSOL belongs and to which he contributed with the high-resolution H-alpha image of the eclipsed Sun.
On the same day of the eclipse, March 29, Prof. Sigismondi participated in the Ticino Astronomical Society's conference describing the importance of observing the partial eclipse. Also fruitful has been the visit to the Specola Solare Ticinese.
8.New cooperation agreement between ICRANet and University of Tartu (UT), November 30, 2024
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On February 3, 2025, we received the news that a new Cooperation agreement between ICRANet and the University of Tartu – UT (Estonia) has been signed on November 30, 2024. The Cooperation Protocol has been signed by Prof. Toomas Asser (Rector of UT)and Prof. Remo Ruffini (Director of ICRANet).
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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/tartu
The text of the agreement:https://www.icranet.org/tartu
9.New cooperation agreement between ICRANet and Univesidad Mayor, December 10, 2024
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On March 13, 2025 we received the news that a new Cooperation agreement between ICRANet and the Universidad Mayor in Santiago de Chile has been signed on December 10, 2024. The Cooperation Protocol has been signed by Prof. Patricio Manque(Rector of Universidad Mayor), Prof. Laura Marcela Becerra Bayona (Universidad Mayor), Prof. Remo Ruffini (Director of ICRANet)and Prof. Jorge A. Rueda H. (ICRANet Faculty Professor).
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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=1575
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1575
10.New cooperation agreement between ICRANet and the Catholic Institute of Technology (CatholicTech), February 4, 2025
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On February 4, 2025, ICRANet has signed a new Cooperation protocol with the Catholic Institute of Technology (CatholicTech) in Castel Gandolfo (Italy). The Cooperation Protocol has been signed by Prof. Alexis Haughey (VP of Research of CatholicTech), Prof. Rodrigo Negreiros (CatholicTech), Prof. Remo Ruffini (Director of ICRANet) and Prof. Jorge A. Rueda H. (ICRANet Faculty Professor).
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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=1550
The text of the agreement: https://www.icranet.org/index.php?option=com_content&task=view&id=1550
11.Renewal of the cooperation agreement between ICRANet and Universidad Industrial de Santander, December 2, 2024
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On March 17, 2025 we received the news that the Cooperation agreement between ICRANet and the Universidad Industrial de Santander (UIS) has been renewed on December 2, 2024. The renewal was signed by Prof. Hernan Porras Diaz (Rector of UIS) and by Prof. Remo Ruffini (Director of ICRANet).
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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: https://www.icranet.org/UIS
The text of the agreement: https://www.icranet.org/UIS
12.Renewal of the cooperation agreement between ICRANet and Universidad Del Valle, March 21, 2025
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On March 21, 2025, the Cooperation Agreement between ICRANet and the Universidad Del Valle (Colombia) has been renewed. The renewal was signed by Dr. Guillermo Murillo Vargas, Cesar Alonso Velanzuela Toledo, Vicerrectora Académica, Vicerrector de Investigaciones, Direccion de Relaciones Internacionales, Oficina Juridica (for Universidad Del Valle) and by Prof. Remo Ruffini (Director of ICRANet).
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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/univDelValle
The text of the agreement:http://www.icranet.org/univDelValle
13.Renewal of the cooperation agreement between ICRANet and the LEPL-Ivane Javakhishvili Tbilisi State University (TSU), February 6, 2025
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On February 6, 2025, the Cooperation Agreement between ICRANet and the LEPL-Ivane Javakhishvili Tbilisi State University – TSU (Georgia) has been renewed. The renewal was signed by Prof. Jaba Samushia (Rector of TSU) and by Prof. Remo Ruffini (Director of ICRANet).
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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/tsu
The text of the agreement:http://www.icranet.org/tsu
14.Scientific visits to ICRANet
- Massimo Della Valle (INAF), February 2 - 4, March 1-2, 2025;
- Ridha Fathima Mohideen Malik (University of Ferrara), February 4 - 6, 2025;
- Nurkamal Shynggyskhan (Al-Farabi Kazakh National University), February 5–March 8, 2025;
- Berkimbayev Daulet (Al-Farabi Kazakh National University), February 5 – March 10, 2025;
- Guldana Rabigulova (Al-Farabi Kazakh National University), March 20 -26, 2025;
- Mikalai Prakapenia (Belarusian State University), March 22-28, 2025.
15.Scientific visits to ICRANet
MAGIC collaboration, Characterization of Markarian 421 during its most violent year: Multiwavelength variability and correlations, published in Astronomy & Astrophysics, Volume 694 on February 2025.
Aims.Mrk 421 was in its most active state around early 2010, which led to the highest TeV gamma-ray flux ever recorded from any active galactic nuclei (AGN). We aim to characterize the multiwavelength behavior during this exceptional year for Mrk 421, and evaluate whether it is consistent with the picture derived with data from other less exceptional years. Methods. We investigated the period from November 5, 2009, (MJD 55140) until July 3, 2010, (MJD 55380) with extensive coverage from very-high-energy (VHE; E > 100 GeV) gamma rays to radio with MAGIC, VERITAS, Fermi-LAT, RXTE, Swift, GASP-WEBT, VLBA, and a variety of additional optical and radio telescopes. We characterized the variability by deriving fractional variabilities as well as power spectral densities (PSDs). In addition, we investigated images of the jet taken with VLBA and the correlation behavior among different energy bands. Results.Mrk 421 was in widely different states of activity throughout the campaign, ranging from a low-emission state to its highest VHE flux ever recorded. We find the strongest variability in X-rays and VHE gamma rays, and PSDs compatible with power-law functions with indices around 1.5. We observe strong correlations between X-rays and VHE gamma rays at zero time lag with varying characteristics depending on the exact energy band. We also report a marginally significant (∼3σ) positive correlation between high-energy (HE; E > 100 MeV) gamma rays and the ultraviolet band. We detected marginally significant (∼3σ) correlations between the HE and VHE gamma rays, and between HE gamma rays and the X-ray, that disappear when the large flare in February 2010 is excluded from the correlation study, hence indicating the exceptionality of this flaring event in comparison with the rest of the campaign. The 2010 violent activity of Mrk 421 also yielded the first ejection of features in the VLBA images of the jet of Mrk 421. Yet the large uncertainties in the ejection times of these unprecedented radio features prevent us from firmly associating them to the specific flares recorded during the 2010 campaign. We also show that the collected multi-instrument data are consistent with a scenario where the emission is dominated by two regions, a compact and extended zone, which could be considered as a simplified implementation of an energy-stratified jet as suggested by recent IXPE observations.
DOI: https://doi.org/10.1051/0004-6361/202451624
MAGIC collaboration, Time-dependent modelling of short-term variability in the TeV-blazar VER J0521+211 during the major flare in 2020, published in Astronomy & Astrophysics, Volume 694 on February 2025.
The BL Lacertaeobject VER J0521+211 underwent a notable flaring episode in February 2020. A short-term monitoring campaign, led by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) collaboration, covering a wide energy range from radio to very high-energy (VHE, 100 GeV < E < 100 TeV) gamma rays was organised to study its evolution. These observations resulted in a consistent detection of the source over six consecutive nights in the VHE gamma-ray domain. Combining these nightly observations with an extensive set of multi-wavelength data made modelling of the blazar's spectral energy distribution (SED) possible during the flare. This modelling was performed with a focus on two plausible emission mechanisms: (i) a leptonic two-zone synchrotron-self-Compton scenario, and (ii) a lepto-hadronic one-zone scenario. Both models effectively replicated the observed SED from radio to the VHE gamma-ray band. Furthermore, by introducing a set of evolving parameters, both models were successful in reproducing the evolution of the fluxes measured in different bands throughout the observing campaign. Notably, the lepto-hadronic model predicts enhanced photon and neutrino fluxes at ultra-high energies (E > 100 TeV). While the photon component, generated via decay of neutral pions, is not directly observable as it is subject to intense pair production (and therefore extinction) through interactions with the cosmic microwave background photons, neutrino detectors (e.g. IceCube) can probe the predicted neutrino component. Finally, the analysis of the gamma-ray spectra, observed by MAGIC and the Fermi-LAT telescopes, yielded a conservative 95% confidence upper limit of z ≤ 0.244 for the redshift of this blazar.
DOI: https://doi.org/10.1051/0004-6361/202451378
Liu, Yang; Li, Jie; Gao, Linqing; Zhang, Haotong; Xu, Zhenghua; Wang, Yu; Lin, Wenbin, Deep Learning for Identification and Characterization of Ca II Absorption Lines: A Multitask Convolutional Neural Network Approach, published in The Astrophysical Journal Supplement Series, Volume 276, Issue 2 on February 2025.
Quasar absorption lines are a powerful tool for studying the Universe, enabling us to probe distant gas, dust, and galaxy formation and evolution. However, detecting these lines, particularly Ca II absorption lines, is a time-consuming and laborious process. Existing deep learning methods are prone to false positives and still require extensive manual verification and parameter measurement. This work presents three multitask convolutional neural network models and identifies the ResNet-CBAM model, which incorporates residual learning and an attention mechanism as the most effective. The results show that the ResNet-CBAM model achieves an accuracy of 99.7% in detecting Ca II absorbers and excels in predicting critical parameters such as equivalent width and full width at half-maximum, with average correlation coefficients of 0.98 and 0.85, respectively. Furthermore, its remarkable generalization ability significantly improves detection precision on unseen data, rising from 20.3% of the cutting-edge model to 92.6%. In addition, with our numerous optimizations, our method can directly search for nonnormalized data, still achieving an accuracy of 98.6%. This translates to a dramatic reduction in manual inspection workload, paving the way for efficient and automated Ca II absorber identification. In real-world applications on the Sloan Digital Sky Survey DR7 and DR12, our model successfully rediscovered 321 known Ca II absorbers while identifying potential candidates in an additional 381 spectra. The codes used in this paper are available on Zenodo at doi:10.5281/zenodo.13953656.
DOI: https://doi.org/10.3847/1538-4365/ad9250
Prakapenia, Mikalai; Vereshchagin, Gregory, Pair creation from radial electromagnetic perturbation of a compact astrophysical object, published in Physical Review D, Volume 111, Issue 4 on February 2025.
Recently Usov's mechanism of pair creation on the surface of compact astrophysical objects has been revisited with a conclusion that the pair creation rate was previously underestimated in the literature by nearly two orders of magnitude. Here we consider an alternative hypothesis of pair creation due to a perturbation of the surface of a compact object. Radial perturbation is induced in hydrodynamic velocity resulting in a microscopic displacement of the negatively charged component with respect to the positively charged one. The result depends on the ratio between the spatial scale of the perturbation λ and the mean free path l. When λ∼l the perturbation energy is converted into a burst of electron-positron pairs that are created in collisionless plasma oscillations at the surface; after energy excess is dissipated, the electrosphere returns to its electrostatic configuration. When instead λ≫l, the perturbation is thermalized, its energy is transformed into heat, and pairs are created continuously by the heated electrosphere. We discuss the relevant astrophysical scenarios.
DOI: https://doi.org/10.1103/PhysRevD.111.043023
Ruffini, Remo; Prakapenia, Mikalai; Quevedo, Hernando; Zhang, Shurui, Single versus the Repetitive Penrose Process in a Kerr Black Hole, published in Physical Review Letters, Volume 134, Issue 8 on February 2025.
Extracting the rotational energy from a Kerr black hole (BH) is one of the crucial topics in relativistic astrophysics. Here, we give special attention to the Penrose ballistic process based on the fission of a massive particle μ0 into two particles μ1 and μ2, occurring in the ergosphere of a Kerr BH. Bardeen et al. indicated that for the process to occur, some additional "hydrodynamical forces or superstrong radiation reactions" were needed. Wald and Chandrasekhar further expanded this idea. This animosity convinced Piran and collaborators to move from a simple three-body system characterizing the original Penrose process to a many-body system. This many-body approach was further largely expanded by others, some questionable in their validity. Here, we return to the simplest original Penrose process and show that the solution of the equations of motion, imposing the turning point condition on their trajectories, leads to the rotational energy extraction from the BH expected by Penrose. The efficiency of energy extraction by a single process is quantified for three different single decay processes occurring, respectively, at r=1.2M, r=1.5M, and r=1.9M. An interesting repetitive model has been proposed by Misner et al. [Gravitation (W. H. Freeman, San Francisco, 1973)]. Indeed, it would appear that a repetitive sequence of 246 decays of the above injection process at r=1.2M and the corresponding ones at r=1.5M and r=1.9M could extract 100% of the rotational energy of the BH, so violating energy conservation. The accompanying article, accounting for the existence of the BH irreducible mass, introduces a nonlinear approach that avoids violating energy conservation and leads to a new energy extraction process.
DOI: https://doi.org/10.1103/PhysRevLett.134.081403
Ruffini, R.; Bianco, C. L.; Prakapenia, M.; Quevedo, H.; Rueda, J. A.; Zhang, S., Role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole, published in Physical Review Research, Volume 7, Issue 1 on February 2025. 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=16πMirr2. 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 nonrotating 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.
DOI: https://doi.org/10.1103/PhysRevResearch.7.013203
Valerin, G.; Pastorello, A.; Reguitti, A.; Benetti, S.; Cai, Y. -Z.; Chen, T. -W.; Eappachen, D.; Elias-Rosa, N.; Fraser, M.; Gangopadhyay, A.; Hsiao, E. Y.; Howell, D. A.; Inserra, C.; Izzo, L.; Jencson, J.; Kankare, E.; Kotak, R.; Mazzali, P. A.; Misra, K.; Pignata, G.; Prentice, S. J.; Sand, D. J.; Smartt, S. J.; Stritzinger, M. D.; Tartaglia, L.; Valenti, S.; Anderson, J. P.; Andrews, J. E.; Amaro, R. C.; Brennan, S.; Bufano, F.; Callis, E.; Cappellaro, E.; Dastidar, R.; Della Valle, M.; Fiore, A.; Fulton, M. D.; Galbany, L.; Heikkilä, T.; Hiramatsu, D.; Karamehmetoglu, E.; Kuncarayakti, H.; Leloudas, G.; Lundquist, M.; McCully, C.; Müller-Bravo, T. E.; Nicholl, M.; Ochner, P.; Padilla Gonzalez, E.; Paraskeva, E.; Pellegrino, C.; Rau, A.; Reichart, D. E.; Reynolds, T. M.; Roy, R.; Salmaso, I.; Singh, M.; Turatto, M.; Tomasella, L.; Wyatt, S.; Young, D. R., A study in scarlet: I. Photometric properties of a sample of intermediate-luminosity red transients, Astronomy & Astrophysics, 695, A42 (2025).
Aims. We investigate the photometric characteristics of a sample of intermediate-luminosity red transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. Our goal is to provide a stepping stone in the path to reveal the physical origin of such events, thanks to the analysis of the datasets collected. Methods. We present the multi-wavelength photometric follow-up of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd, and AT 2019udc. Through the analysis and modelling of their spectral energy distribution and bolometric light curves, we inferred the physical parameters associated with these transients. Results. All four objects display a single-peaked light curve which ends in a linear decline in magnitudes at late phases. A flux excess with respect to a single blackbody emission is detected in the infrared domain for three objects in our sample, a few months after maximum. This feature, commonly found in ILRTs, is interpreted as a sign of dust formation. Mid-infrared monitoring of NGC 300 2008OT-1 761 days after maximum allowed us to infer the presence of ∼10−3–10−5 M⊙ of dust, depending on the chemical composition and the grain size adopted. The late-time decline of the bolometric light curves of the considered ILRTs is shallower than expected for 56Ni decay, hence requiring an additional powering mechanism. James Webb Space Telescope observations of AT 2019abn prove that the object has faded below its progenitor luminosity in the mid-infrared domain, five years after its peak. Together with the disappearance of NGC 300 2008OT-1 in Spitzer images seven years after its discovery, this supports the terminal explosion scenario for ILRTs. With a simple semi-analytical model we tried to reproduce the observed bolometric light curves in the context of a few solar masses ejected at few 103 km s−1 and enshrouded in an optically thick circumstellar medium.
DOI: https://doi.org/10.1051/0004-6361/202451733
Sigismondi, Costantino, FomahantAquarii, CorScorpii Antares e ilprincipe Federico Cristiano di Sassonia a S. Maria degliAngeli, published in BALMER, vol. 3 pp. 1-10 on March 2025.
A celebrative plaque nearly canceled is located near the 205 position of the Clementine Gnomon in Rome: the prince Friedrich Christian of Poland and Saxony observed the culmination of Fomahant (former transliteration of Fomalhaut) on 6 december 1738 at 11:22:38. The historical circumstances of this event are presented: the young prince, 16 years old, was heading to Naples, in order to find a cure for his back, touching all the most important cities of Italy. In Rome he met the Pope and he was guest of the Cardinal AnnibaleAlbani, nefew of Clement XI, the financer of the meridian line. Albani played also a major role in the conversion to Catholicism of the King Augustus III, father of Friedrich Christian. The daily observation of a stellar transit, slightly before the solar meridian transit, was a veritable cameo in this Grand Tour of the prince. The astronomical circumstances and the astrometric data suggest that the star observed was rather Antares, and a telescope at least 2 m high was necessary to spot the star from the Capricorn side of the meridian line. An astronomer, very expert of the observations of that gigantic meridian line, had to be present in the Basilica to show to the prince that phenomenon so difficult to be observed. Father Roger Boscovich, who 12 years later calibrated accurately the gnomon could have been the astronomer. The history of Fomalhaut which passed from Aquarius to the Southern Fish is also drafted.
MAGIC collaboration, Combined search in dwarf spheroidal galaxies for branon dark matter annihilation signatures with the MAGIC telescopes, published in Journal of Cosmology and Astroparticle Physics, Volume 2025, on March 2025.
Massive brane fluctuations, called branons, behave as weakly interacting massive particles, which is one of the most favored class of candidates to fulfill the role of the dark matter (DM), an elusive kind of matter beyond the Standard Model. We present a multi-target search in dwarf spheroidal galaxies for branon DM annihilation signatures with a total exposure of 354 hours with the ground-based gamma-ray telescope system MAGIC. This search led to the most constraining limits on branon DM in the sub-TeV and multi-TeV DM mass range. Our most stringent limit on the thermally-averaged annihilation cross-section (at 95% confidence level) corresponds to ⟨σv⟩≃ 1.9 × 10-24 cm3s-1 at a branon mass of ∼ 1.5 TeV.
DOI: https://doi.org/10.1088/1475-7516/2025/03/020
Pace, C. M., The Correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman Metrics When the Cosmological Constant Is Greater than Zero, published in Journal of Modern Physics, 16, 441-482 on March 27, 2025.
In a recent article we have corrected the traditional derivation of the Schwarzschild metric when the cosmological constant is equal to zero, thus obtaining the formulation of the correct Schwarzschild metric when the cosmological constant is equal to zero, which formulation is different from that of the traditional Schwarzschild metric when the cosmological constant is equal to zero. Then, in another article by starting from this correct Schwarzschild metric when the cosmological constant is equal to zero, we have corrected also the Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is equal to zero. In this article, by starting from these correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is equal to zero, we obtain the formulations of the correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is greater than zero. Moreover, we analyse these correct results and their consequences. Finally, we propose some possible crucial experiments between the commonly accepted theory and the same theory corrected according to this article.
DOI: https://doi.org/10.4236/jmp.2025.163024
She-Sheng Xue, Particle-antiparticle oscillation modes crossing horizon: Baryogenesis and dark-matter waves, Nucl. Phys. B 1014 (2025) 116875.
Quantum massive particle and antiparticle pair production and oscillation during reheating result in a holographic and massive pair plasma state. Perturbations in the densities of particles and antiparticles within this plasma form acoustic waves, characterized by symmetric and asymmetric density contrasts. By deriving the acoustic wave equations and identifying the frequencies of the lowest-lying perturbation modes (with zero wave number), the study shows that the wavelengths of these modes, when compared with the horizon size, suggest the possibility of superhorizon crossing during reheating. This crossing leads to particle-antiparticle asymmetry observable by an observer inside the horizon. The decay of massive particles and antiparticles into baryons generates a net baryon number, potentially explaining baryogenesis. The calculated baryon number-to-entropy ratio aligns with observational data. This crossing also accounts for dark matter particle-antiparticle asymmetry in the present Universe. The study also explores perturbation modes with nonzero wave numbers, representing dark-matter acoustic waves. These modes exited the horizon and re-entered after recombination, potentially imprinting on the matter power spectrum at large length scales and influencing the formation of large-scale structures and galaxies.
DOI: https://doi.org/10.1016/j.nuclphysb.2025.116875
Aims.Mrk 421 was in its most active state around early 2010, which led to the highest TeV gamma-ray flux ever recorded from any active galactic nuclei (AGN). We aim to characterize the multiwavelength behavior during this exceptional year for Mrk 421, and evaluate whether it is consistent with the picture derived with data from other less exceptional years. Methods. We investigated the period from November 5, 2009, (MJD 55140) until July 3, 2010, (MJD 55380) with extensive coverage from very-high-energy (VHE; E > 100 GeV) gamma rays to radio with MAGIC, VERITAS, Fermi-LAT, RXTE, Swift, GASP-WEBT, VLBA, and a variety of additional optical and radio telescopes. We characterized the variability by deriving fractional variabilities as well as power spectral densities (PSDs). In addition, we investigated images of the jet taken with VLBA and the correlation behavior among different energy bands. Results.Mrk 421 was in widely different states of activity throughout the campaign, ranging from a low-emission state to its highest VHE flux ever recorded. We find the strongest variability in X-rays and VHE gamma rays, and PSDs compatible with power-law functions with indices around 1.5. We observe strong correlations between X-rays and VHE gamma rays at zero time lag with varying characteristics depending on the exact energy band. We also report a marginally significant (∼3σ) positive correlation between high-energy (HE; E > 100 MeV) gamma rays and the ultraviolet band. We detected marginally significant (∼3σ) correlations between the HE and VHE gamma rays, and between HE gamma rays and the X-ray, that disappear when the large flare in February 2010 is excluded from the correlation study, hence indicating the exceptionality of this flaring event in comparison with the rest of the campaign. The 2010 violent activity of Mrk 421 also yielded the first ejection of features in the VLBA images of the jet of Mrk 421. Yet the large uncertainties in the ejection times of these unprecedented radio features prevent us from firmly associating them to the specific flares recorded during the 2010 campaign. We also show that the collected multi-instrument data are consistent with a scenario where the emission is dominated by two regions, a compact and extended zone, which could be considered as a simplified implementation of an energy-stratified jet as suggested by recent IXPE observations.
DOI: https://doi.org/10.1051/0004-6361/202451624
MAGIC collaboration, Time-dependent modelling of short-term variability in the TeV-blazar VER J0521+211 during the major flare in 2020, published in Astronomy & Astrophysics, Volume 694 on February 2025.
The BL Lacertaeobject VER J0521+211 underwent a notable flaring episode in February 2020. A short-term monitoring campaign, led by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) collaboration, covering a wide energy range from radio to very high-energy (VHE, 100 GeV < E < 100 TeV) gamma rays was organised to study its evolution. These observations resulted in a consistent detection of the source over six consecutive nights in the VHE gamma-ray domain. Combining these nightly observations with an extensive set of multi-wavelength data made modelling of the blazar's spectral energy distribution (SED) possible during the flare. This modelling was performed with a focus on two plausible emission mechanisms: (i) a leptonic two-zone synchrotron-self-Compton scenario, and (ii) a lepto-hadronic one-zone scenario. Both models effectively replicated the observed SED from radio to the VHE gamma-ray band. Furthermore, by introducing a set of evolving parameters, both models were successful in reproducing the evolution of the fluxes measured in different bands throughout the observing campaign. Notably, the lepto-hadronic model predicts enhanced photon and neutrino fluxes at ultra-high energies (E > 100 TeV). While the photon component, generated via decay of neutral pions, is not directly observable as it is subject to intense pair production (and therefore extinction) through interactions with the cosmic microwave background photons, neutrino detectors (e.g. IceCube) can probe the predicted neutrino component. Finally, the analysis of the gamma-ray spectra, observed by MAGIC and the Fermi-LAT telescopes, yielded a conservative 95% confidence upper limit of z ≤ 0.244 for the redshift of this blazar.
DOI: https://doi.org/10.1051/0004-6361/202451378
Liu, Yang; Li, Jie; Gao, Linqing; Zhang, Haotong; Xu, Zhenghua; Wang, Yu; Lin, Wenbin, Deep Learning for Identification and Characterization of Ca II Absorption Lines: A Multitask Convolutional Neural Network Approach, published in The Astrophysical Journal Supplement Series, Volume 276, Issue 2 on February 2025.
Quasar absorption lines are a powerful tool for studying the Universe, enabling us to probe distant gas, dust, and galaxy formation and evolution. However, detecting these lines, particularly Ca II absorption lines, is a time-consuming and laborious process. Existing deep learning methods are prone to false positives and still require extensive manual verification and parameter measurement. This work presents three multitask convolutional neural network models and identifies the ResNet-CBAM model, which incorporates residual learning and an attention mechanism as the most effective. The results show that the ResNet-CBAM model achieves an accuracy of 99.7% in detecting Ca II absorbers and excels in predicting critical parameters such as equivalent width and full width at half-maximum, with average correlation coefficients of 0.98 and 0.85, respectively. Furthermore, its remarkable generalization ability significantly improves detection precision on unseen data, rising from 20.3% of the cutting-edge model to 92.6%. In addition, with our numerous optimizations, our method can directly search for nonnormalized data, still achieving an accuracy of 98.6%. This translates to a dramatic reduction in manual inspection workload, paving the way for efficient and automated Ca II absorber identification. In real-world applications on the Sloan Digital Sky Survey DR7 and DR12, our model successfully rediscovered 321 known Ca II absorbers while identifying potential candidates in an additional 381 spectra. The codes used in this paper are available on Zenodo at doi:10.5281/zenodo.13953656.
DOI: https://doi.org/10.3847/1538-4365/ad9250
Prakapenia, Mikalai; Vereshchagin, Gregory, Pair creation from radial electromagnetic perturbation of a compact astrophysical object, published in Physical Review D, Volume 111, Issue 4 on February 2025.
Recently Usov's mechanism of pair creation on the surface of compact astrophysical objects has been revisited with a conclusion that the pair creation rate was previously underestimated in the literature by nearly two orders of magnitude. Here we consider an alternative hypothesis of pair creation due to a perturbation of the surface of a compact object. Radial perturbation is induced in hydrodynamic velocity resulting in a microscopic displacement of the negatively charged component with respect to the positively charged one. The result depends on the ratio between the spatial scale of the perturbation λ and the mean free path l. When λ∼l the perturbation energy is converted into a burst of electron-positron pairs that are created in collisionless plasma oscillations at the surface; after energy excess is dissipated, the electrosphere returns to its electrostatic configuration. When instead λ≫l, the perturbation is thermalized, its energy is transformed into heat, and pairs are created continuously by the heated electrosphere. We discuss the relevant astrophysical scenarios.
DOI: https://doi.org/10.1103/PhysRevD.111.043023
Ruffini, Remo; Prakapenia, Mikalai; Quevedo, Hernando; Zhang, Shurui, Single versus the Repetitive Penrose Process in a Kerr Black Hole, published in Physical Review Letters, Volume 134, Issue 8 on February 2025.
Extracting the rotational energy from a Kerr black hole (BH) is one of the crucial topics in relativistic astrophysics. Here, we give special attention to the Penrose ballistic process based on the fission of a massive particle μ0 into two particles μ1 and μ2, occurring in the ergosphere of a Kerr BH. Bardeen et al. indicated that for the process to occur, some additional "hydrodynamical forces or superstrong radiation reactions" were needed. Wald and Chandrasekhar further expanded this idea. This animosity convinced Piran and collaborators to move from a simple three-body system characterizing the original Penrose process to a many-body system. This many-body approach was further largely expanded by others, some questionable in their validity. Here, we return to the simplest original Penrose process and show that the solution of the equations of motion, imposing the turning point condition on their trajectories, leads to the rotational energy extraction from the BH expected by Penrose. The efficiency of energy extraction by a single process is quantified for three different single decay processes occurring, respectively, at r=1.2M, r=1.5M, and r=1.9M. An interesting repetitive model has been proposed by Misner et al. [Gravitation (W. H. Freeman, San Francisco, 1973)]. Indeed, it would appear that a repetitive sequence of 246 decays of the above injection process at r=1.2M and the corresponding ones at r=1.5M and r=1.9M could extract 100% of the rotational energy of the BH, so violating energy conservation. The accompanying article, accounting for the existence of the BH irreducible mass, introduces a nonlinear approach that avoids violating energy conservation and leads to a new energy extraction process.
DOI: https://doi.org/10.1103/PhysRevLett.134.081403
Ruffini, R.; Bianco, C. L.; Prakapenia, M.; Quevedo, H.; Rueda, J. A.; Zhang, S., Role of the irreducible mass in repetitive Penrose energy extraction processes in a Kerr black hole, published in Physical Review Research, Volume 7, Issue 1 on February 2025. 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=16πMirr2. 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 nonrotating 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.
DOI: https://doi.org/10.1103/PhysRevResearch.7.013203
Valerin, G.; Pastorello, A.; Reguitti, A.; Benetti, S.; Cai, Y. -Z.; Chen, T. -W.; Eappachen, D.; Elias-Rosa, N.; Fraser, M.; Gangopadhyay, A.; Hsiao, E. Y.; Howell, D. A.; Inserra, C.; Izzo, L.; Jencson, J.; Kankare, E.; Kotak, R.; Mazzali, P. A.; Misra, K.; Pignata, G.; Prentice, S. J.; Sand, D. J.; Smartt, S. J.; Stritzinger, M. D.; Tartaglia, L.; Valenti, S.; Anderson, J. P.; Andrews, J. E.; Amaro, R. C.; Brennan, S.; Bufano, F.; Callis, E.; Cappellaro, E.; Dastidar, R.; Della Valle, M.; Fiore, A.; Fulton, M. D.; Galbany, L.; Heikkilä, T.; Hiramatsu, D.; Karamehmetoglu, E.; Kuncarayakti, H.; Leloudas, G.; Lundquist, M.; McCully, C.; Müller-Bravo, T. E.; Nicholl, M.; Ochner, P.; Padilla Gonzalez, E.; Paraskeva, E.; Pellegrino, C.; Rau, A.; Reichart, D. E.; Reynolds, T. M.; Roy, R.; Salmaso, I.; Singh, M.; Turatto, M.; Tomasella, L.; Wyatt, S.; Young, D. R., A study in scarlet: I. Photometric properties of a sample of intermediate-luminosity red transients, Astronomy & Astrophysics, 695, A42 (2025).
Aims. We investigate the photometric characteristics of a sample of intermediate-luminosity red transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. Our goal is to provide a stepping stone in the path to reveal the physical origin of such events, thanks to the analysis of the datasets collected. Methods. We present the multi-wavelength photometric follow-up of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd, and AT 2019udc. Through the analysis and modelling of their spectral energy distribution and bolometric light curves, we inferred the physical parameters associated with these transients. Results. All four objects display a single-peaked light curve which ends in a linear decline in magnitudes at late phases. A flux excess with respect to a single blackbody emission is detected in the infrared domain for three objects in our sample, a few months after maximum. This feature, commonly found in ILRTs, is interpreted as a sign of dust formation. Mid-infrared monitoring of NGC 300 2008OT-1 761 days after maximum allowed us to infer the presence of ∼10−3–10−5 M⊙ of dust, depending on the chemical composition and the grain size adopted. The late-time decline of the bolometric light curves of the considered ILRTs is shallower than expected for 56Ni decay, hence requiring an additional powering mechanism. James Webb Space Telescope observations of AT 2019abn prove that the object has faded below its progenitor luminosity in the mid-infrared domain, five years after its peak. Together with the disappearance of NGC 300 2008OT-1 in Spitzer images seven years after its discovery, this supports the terminal explosion scenario for ILRTs. With a simple semi-analytical model we tried to reproduce the observed bolometric light curves in the context of a few solar masses ejected at few 103 km s−1 and enshrouded in an optically thick circumstellar medium.
DOI: https://doi.org/10.1051/0004-6361/202451733
Sigismondi, Costantino, FomahantAquarii, CorScorpii Antares e ilprincipe Federico Cristiano di Sassonia a S. Maria degliAngeli, published in BALMER, vol. 3 pp. 1-10 on March 2025.
A celebrative plaque nearly canceled is located near the 205 position of the Clementine Gnomon in Rome: the prince Friedrich Christian of Poland and Saxony observed the culmination of Fomahant (former transliteration of Fomalhaut) on 6 december 1738 at 11:22:38. The historical circumstances of this event are presented: the young prince, 16 years old, was heading to Naples, in order to find a cure for his back, touching all the most important cities of Italy. In Rome he met the Pope and he was guest of the Cardinal AnnibaleAlbani, nefew of Clement XI, the financer of the meridian line. Albani played also a major role in the conversion to Catholicism of the King Augustus III, father of Friedrich Christian. The daily observation of a stellar transit, slightly before the solar meridian transit, was a veritable cameo in this Grand Tour of the prince. The astronomical circumstances and the astrometric data suggest that the star observed was rather Antares, and a telescope at least 2 m high was necessary to spot the star from the Capricorn side of the meridian line. An astronomer, very expert of the observations of that gigantic meridian line, had to be present in the Basilica to show to the prince that phenomenon so difficult to be observed. Father Roger Boscovich, who 12 years later calibrated accurately the gnomon could have been the astronomer. The history of Fomalhaut which passed from Aquarius to the Southern Fish is also drafted.
MAGIC collaboration, Combined search in dwarf spheroidal galaxies for branon dark matter annihilation signatures with the MAGIC telescopes, published in Journal of Cosmology and Astroparticle Physics, Volume 2025, on March 2025.
Massive brane fluctuations, called branons, behave as weakly interacting massive particles, which is one of the most favored class of candidates to fulfill the role of the dark matter (DM), an elusive kind of matter beyond the Standard Model. We present a multi-target search in dwarf spheroidal galaxies for branon DM annihilation signatures with a total exposure of 354 hours with the ground-based gamma-ray telescope system MAGIC. This search led to the most constraining limits on branon DM in the sub-TeV and multi-TeV DM mass range. Our most stringent limit on the thermally-averaged annihilation cross-section (at 95% confidence level) corresponds to ⟨σv⟩≃ 1.9 × 10-24 cm3s-1 at a branon mass of ∼ 1.5 TeV.
DOI: https://doi.org/10.1088/1475-7516/2025/03/020
Pace, C. M., The Correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman Metrics When the Cosmological Constant Is Greater than Zero, published in Journal of Modern Physics, 16, 441-482 on March 27, 2025.
In a recent article we have corrected the traditional derivation of the Schwarzschild metric when the cosmological constant is equal to zero, thus obtaining the formulation of the correct Schwarzschild metric when the cosmological constant is equal to zero, which formulation is different from that of the traditional Schwarzschild metric when the cosmological constant is equal to zero. Then, in another article by starting from this correct Schwarzschild metric when the cosmological constant is equal to zero, we have corrected also the Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is equal to zero. In this article, by starting from these correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is equal to zero, we obtain the formulations of the correct Schwarzschild, Reissner-Nordstrøm, Kerr and Kerr-Newman metrics when the cosmological constant is greater than zero. Moreover, we analyse these correct results and their consequences. Finally, we propose some possible crucial experiments between the commonly accepted theory and the same theory corrected according to this article.
DOI: https://doi.org/10.4236/jmp.2025.163024
She-Sheng Xue, Particle-antiparticle oscillation modes crossing horizon: Baryogenesis and dark-matter waves, Nucl. Phys. B 1014 (2025) 116875.
Quantum massive particle and antiparticle pair production and oscillation during reheating result in a holographic and massive pair plasma state. Perturbations in the densities of particles and antiparticles within this plasma form acoustic waves, characterized by symmetric and asymmetric density contrasts. By deriving the acoustic wave equations and identifying the frequencies of the lowest-lying perturbation modes (with zero wave number), the study shows that the wavelengths of these modes, when compared with the horizon size, suggest the possibility of superhorizon crossing during reheating. This crossing leads to particle-antiparticle asymmetry observable by an observer inside the horizon. The decay of massive particles and antiparticles into baryons generates a net baryon number, potentially explaining baryogenesis. The calculated baryon number-to-entropy ratio aligns with observational data. This crossing also accounts for dark matter particle-antiparticle asymmetry in the present Universe. The study also explores perturbation modes with nonzero wave numbers, representing dark-matter acoustic waves. These modes exited the horizon and re-entered after recombination, potentially imprinting on the matter power spectrum at large length scales and influencing the formation of large-scale structures and galaxies.
DOI: https://doi.org/10.1016/j.nuclphysb.2025.116875