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  ICRANet Newsletter
ICRANet Newsletter
December 2024 - January 2025
SUMMARY
1. ICRANet recent paper accepted for publication in Physical Review Letters 2. Prof. Ruffini participation in “How dreams come true. A workshop honoring the contribution of Enrico Costa to Science”, December 10-12, Rome (Italy) 3. Prof. Ruffini participation in the “26thRAGtime workshop”, December 9-13, Opava (Czech Republic) and online 4. Prof. Ruffini participation in the conference “High energy astrophysics today and tomorrow 2024 (HEA-2024)”, December 23-26, Moscow (Russia) and online 5.Visit of Prof. Gregory Vereshchagin to the Astronomical Observatory of Belgrade in Serbia, December 8-12, 2024 6.New cooperation agreement between ICRANet and the Astronomical Observatory of Belgrade (AOB), December 10, 2024 7.New cooperation agreement between ICRANet and Universidad Federal do Cariri (UFCA), January 15, 2025 8. Renewal of the cooperation protocol between ICRANet and the University of Sharjah (UoS), December 9, 2024 9. Renewal of the framework agreement between ICRANet and the University Campus Bio-Medicoof Rome, December 17, 2024 10.Renewal of the cooperation protocol between ICRANet and the Silesian University in Opava, December 18, 2024 11. Renewal of the cooperation protocol between ICRANet and Universidade Federal do Rio Grande do Sul (UFRGS – IFUFRGS), January 8, 2025 12.Prof. Costantino Sigismondi awarded by the National Academy of Lincei, December 10, 2024 13. Behzad Eslampanah awarded as one of the best researchers in Mazandaran Province for 2024, December 22, 2024 14.Scientific visits to ICRANet 15.Recent publications
1.ICRANet recent paper accepted for publication in Physical Review Letters
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.
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 T. 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, Thorne \& Wheeler (hereafter MTW73). 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 paper, accounting for the existence of the BH irreducible mass, introduces a non-linear approach that avoids violating energy conservation and leads to a new energy extraction process.
2.Prof. Ruffini participation in “How dreams come true. A workshop honoring the contribution of Enrico Costa to Science”, December 10-12, Rome (Italy)
From December 10 to 12, 2024, Prof. Ruffini (Director of ICRANet) has been invited to participate as a speaker in the workshop“How dreams come true. A workshop honoring the contribution of Enrico Costa to Science”. This meeting has been organized by INAF IAPS in Rome in celebration of Prof. Enrico Costa 80th birthday. It wanted to highlight only the most important contributions so far to the development of experiments in physics and astronomy: this includes the era of balloon flights until the end of the '80s with FIGARO (French- Italian Gamma Ray Observatory), LAPEX, the precursor of BeppoSAX PDS, and SUGAR (Supernova Gamma-Ray), then the Stellar X-ray Polarimeter (SXRP), which was built and calibrated but unfortunately never flown. Then BeppoSAX came with its discovery of the X-ray afterglow and extragalactic origin of Gamma-Ray Bursts, JEM-X onboard INTEGRAL, the design of SuperAGILE onboard AGILE, and now IXPE (the Imaging X-ray Polarimetry Experiment), that brought the third Bruno Rossi Prize to Enrico, after BeppoSAX and AGILE. Besides his participation at all levels in these experiments and missions, Enrico Costa is now continuing to push for new experiments and missions such as HERMES, eXTP, CUSP, Protosphera and R&D in X-ray polarimeters for future experiments. On that occasion, Prof. Ruffini presented a talk titled “Relevant episodes in Beppo-SAX and IXPE”.
The announcement of the meeting:http://ixpe.iaps.inaf.it/ECindex.html
3.Prof. Ruffini participation in the “26thRAGtime workshop”, December 9-13, Opava (Czech Republic) and online
The announcement of the meeting: https://indico.slu.cz/event/27/
4.Prof. Ruffini participation in the conference “High energy astrophysics today and tomorrow 2024 (HEA-2024)”, December 23-26, Moscow (Russia) and online
This conference continues the tradition of annual conferences organized by the High energy astrophysics department at IKI RAS since 2001. 2024 was special year both for the Russian Academy of Sciences, which celebrates its 300th anniversary as well as for the Department of High Energy Astrophysics of IKI RAS, founded 50 years ago. This year, the conference was attended by 200 scientists from Russia and other countries, such as Armenia, Germany, Italy, China, USA, and Finland. It covered a wide range of topics, including the most relevant results from current space and ground-based observatories, along with updates on future missions and their scientific objectives. The main topics of the conference were Cosmology and physics of the early Universe, Galaxy clusters, Galaxies, active galactic nuclei, Compact objects, accretion, X-ray binaries, Supernovae, supernova remnants, gamma-ray bursts, Cosmic rays and neutrinos, Ongoing and future space projects. The emphasis was on the results of the Spektr-RG observatory, but the conference program included also reviews of the results of other modern astrophysical observatories in operation, such as IXPE, HXMT-Insight, Einstein Probe, etc., as well as ground-based telescopes; reports on future projects, both from Russia (MVN, Spektr-UV, Spektr-M) and other countries, were also presented. The website of the meeting: https://heaconf.cosmos.ru/ The video of Prof. Ruffini speech: https://www.youtube.com/watch?v=BJmnocNwN2A
5.Visit of Prof. Gregory Vereshchagin to the Astronomical Observatory of Belgrade in Serbia, December 8-12, 2024
From December 8 to 12, 2024, Prof. Gregory Vereshchagin visited the Astronomical Observatory of Belgrade in Serbia by the invitation of Dr. Mile Karlica. With the Director, Prof. Luca Popovic, he discussed joint collaboration plans in view of the new cooperation agreement signed by the Observatory and ICRANet.
6.New cooperation agreement between ICRANet and the Astronomical Observatory of Belgrade (AOB), December 10, 2024
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1546
7.New cooperation agreement between ICRANet and Universidade Federal do Cariri (UFCA), January 15, 2025
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1547
8.Renewal of the cooperation protocol between ICRANet and the University of Sharjah (UoS), December 9, 2024
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1274
9.Renewal of the framework agreement between ICRANet and the University Campus Bio-Medico of Rome, December 17, 2024
On December 17, 2024, the Cooperation Agreement between ICRANet and the University Campus Bio-Medico of Rome (Italy) has been tacitly renewed. The renewal was signed by Prof. Eugenio Guglielmelli (Rector of the University Campus Bio-Medico) and by Prof. Remo Ruffini (Director of ICRANet). This agreement will be valid for 2 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/index.php?option=com_content&task=view&id=1220
10.Renewal of the cooperation protocol between ICRANet and the Silesian University in Opava, December 18, 2024
The text of the agreement:https://www.icranet.org/documents/renewal_university_opava.pdf
11.Renewal of the cooperation protocol between ICRANet and Universidade Federal do Rio Grande do Sul (UFRGS – IFUFRGS), January 8, 2025
The text of the agreement:https://www.icranet.org/index.php?option=com_content&task=view&id=1016
12.Prof. Costantino Sigismondi awarded by the National Academy of Lincei, December 10, 2024
We are pleased to announce that Prof. Costantino Sigismondi, ICRANet Adjunct Professor and collaborator, was awarded the first prize by the National Academy of Lincei - Fondazione I Lincei per la Scuola - for the best educational project on General Relativity for the year 2023-2024.The official ceremony has been held in Rome at the Academy's headquarters in Palazzo Corsini on December 10, 2024.
The lesson was also attended by students and Professors from the Galileo Galilei High School in Pescara, who are attending the Special School on Solar Flares with ICRANet, organized by Prof. Sigismondi for the current school year (https://www.icranet.org/index.php?option=com_content&task=view&id=1540). The announcement of the ceremony (including the presentation of the lectiomagistralis and the poster): https://www.linceiscuola.it/notizie/premiazione-elaborati-corso-di-scienze-roma-a-a-2023-2024/
13.Behzad Eslampanah awarded as one of the best researchers in Mazandaran Province for 2024, December 22, 2024
It is our great pleasure to announce that Prof. Behzad Eslampanah (ICRANet center in Mazandaran and University of Mazandaran) has been awarded as one of the best researchers in Mazandaran Province for 2024. The official award ceremony has been held on December 22, 2024 at the University of Mazandaran, at the presence of eminent Iranian representatives and scientists.
Fig. 1. Prof. Behzad Eslampanah receiving the award on December 22, 2024 at the University of Mazandaran.
14.Scientific visits to ICRANet
15.Recent publications
Stanislav Komarov, Gregory Vereshchagin, Electromagnetic Field and Radiation of Charged Particles in the Vicinity of Schwarzschild Black Hole, published in Particles, 2025, 8, 1 on December 30, 2024.
We provide a concise review of the problem of calculating the electromagnetic field and radiation of a charged particle in the vicinity of a black hole. The interest in this problem has been revived due to recent progress in multimessenger observations. Many astrophysical models of energy extraction from a black hole involve consideration of such motion and radiation. Our main goal is to highlight the basic assumptions and limitations of various techniques and point out the main conclusions of these studies.
Liang Li and Soroush Shakeri, Time-averaging Polarimetric and Spectral Properties of Gamma-Ray Bursts, published in The Astrophysical Journal Supplement Series, Volume 276, Number 1 on December 24, 2024.
The composition and radiation mechanism of gamma-ray bursts (GRBs) within jets continue to be hotly debated. Investigating the joint polarimetric and spectral properties is crucial for understanding the composition and radiation mechanism of GRBs. Various jet properties, such as "kinetic-energy-dominated" (KED), "Poynting-flux-dominated" (PFD), and "hybrid-dominated" (HD) relativistic outflows, have been inferred from observed GRB spectra, with expectations of differing polarization levels among them. In this study, we analyzed a sample of 27 GRBs detected by the Gamma-ray Burst Monitor on board the NASA Fermi Gamma-ray Space Telescope, focusing on 26 bursts with significant polarization measurements. Our analysis revealed that 16 bursts (62%) were predominantly associated with the "PFD" jet type, while 10 bursts (38%) were classified as HD, implying that photosphere emission may also be a possible mechanism powering the high levels of polarization. Notably, no bursts were identified as KED type. We found distinct polarization properties, with HD-type bursts exhibiting consistently higher polarization levels than PFD-type bursts. We proposed models incorporating ordered and random magnetic field configurations specific to hybrid jets.
MAGIC collaboration, Broadband multi-wavelength properties of M87 during the 2018 EHT campaign including a very high energy flaring episode, published in Astronomy & Astrophysics, Volume 692 on December 2024.
Context. The nearby elliptical galaxy M87 contains one of only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to γ-ray energies) took part in the second M87 EHT campaign. Aims. The goal of this extensive MWL campaign was to better understand the physics of the accreting black hole M87*, the relationship between the inflow and inner jets, and the high-energy particle acceleration. Understanding the complex astrophysics is also a necessary first step towards performing further tests of general relativity. Methods. The MWL campaign took place in April 2018, overlapping with the EHT M87* observations. We present a new, contemporaneous spectral energy distribution (SED) ranging from radio to very high-energy (VHE) γ-rays as well as details of the individual observations and light curves. We also conducted phenomenological modelling to investigate the basic source properties. Results. We present the first VHE γ-ray flare from M87 detected since 2010. The flux above 350 GeV more than doubled within a period of ≈36 hours. We find that the X-ray flux is enhanced by about a factor of two compared to 2017, while the radio and millimetre core fluxes are consistent between 2017 and 2018. We detect evidence for a monotonically increasing jet position angle that corresponds to variations in the bright spot of the EHT image. Conclusions. Our results show the value of continued MWL monitoring together with precision imaging for addressing the origins of high-energy particle acceleration. While we cannot currently pinpoint the precise location where such acceleration takes place, the new VHE γ-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and it emphasises the need for combined image and spectral modelling.
Sahakyan, N.; Vardanyan, V.; Giommi, P.; Bégué, D.; Israyelyan, D.; Harutyunyan, G.; Manvelyan, M.; Khachatryan, M.; Dereli-Bégué, H.; Gasparyan, S., Markarian Multiwavelength Data Center (MMDC): A Tool for Retrieving and Modeling Multitemporal, Multiwavelength, and Multimessenger Data from Blazar Observations, published in The Astronomical Journal, Volume 168 on December 2024.
The Markarian Multiwavelength Data Center (MMDC) is a web-based tool designed for accessing and retrieving multiwavelength and multimessenger data from blazar observations. MMDC facilitates the construction and interactive visualization of time-resolved multiband spectral energy distributions of blazars by integrating (i) archival data from over 80 catalogs and databases, (ii) optical data from all-sky survey facilities such as the All-Sky Automated Survey for Supernovae, Zwicky Transient Facility, and Panoramic Survey Telescope and Rapid Response System, and (iii) newly analyzed data sets in the optical/UV band from Swift-UVOT, in the X-ray band from Swift-X-Ray Telescope and NuSTAR observations, and the high-energy γ-ray band from Fermi-Large Area Telescope observations. MMDC distinguishes itself from other online platforms by the large quantity of available data. For instance, it includes data from all blazar observations by Swift and NuSTAR, as well as the results of detailed spectral analysis in the γ-ray band during different emission states, covering the period from 2008 to 2023. Another important distinguishing feature of MMDC is its ability to enable precise, self-consistent theoretical modeling of the observed data using machine learning algorithms trained on leptonic and lepto-hadronic models, which consider the injection of particles and all relevant cooling processes. MMDC is an innovative tool that significantly enhances blazar research by providing a comprehensive framework for data accessibility, analysis, and theoretical interpretation, thereby advancing our understanding of blazar emissions and the underlying astrophysical processes.
Moradi, R.; Wang, C. W.; Zhang, B.; Wang, Y.; Xiong, S. -L.; Yi, S. -X.; Tan, W. -J.; Karlica, M.; Zhang, S. -N., Temporal and Spectral Analysis of the Unique and Second-brightest Gamma-Ray Burst GRB 230307A: Insights from GECAM and Fermi/GBM Observations, published in The Astrophysical Journal, Volume 977, Issue 2 on December 2024.
In this study, we present the pulse profile of the unique and the second-brightest gamma-ray burst GRB 230307A, and analyze its temporal behavior using a joint GECAM–Fermi Gamma-ray Burst Monitor (GBM) time-resolved spectral analysis. The utilization of GECAM data is advantageous as it successfully captured significant data during the pileup period of the Fermi/GBM. We investigate the evolution of its flux, photon fluence, photon flux, peak energy, and the corresponding hardness–intensity and hardness–flux correlations. The findings within the first 27 s exhibit consistent patterns reported previously, providing valuable insights for comparing observations with predictions from the synchrotron radiation model invoking an expanding shell. Beyond the initial 27 s, we observe a notable transition in the emitted radiation, attributed to high-latitude emission, influenced by the geometric properties of the shells and the relativistic Doppler effects. By modeling the data within the framework of the large-radius internal shock model, we discuss the required parameters as well as the limitations of the model. We conclude that a more complicated synchrotron emission model is needed to fully describe the observational data of GRB 230307A.
Sigismondi, Costantino, Misurare l'altezza del Sole con una camera oscura in casa, published in BALMER, vol. 2 on December 2024.
The measurement of the solar altitude with a precision of an arcminute is possible by using a pinhole camera at home, and recovering exactly the pinhole's height and the position of the pinhole's image on the floor. The accuracy achievable with a 2.5 m pinhole's height camera is enough to obtain the Cassini correction to the atmospheric refraction.
Zen Vasconcellos, César A.; Hess, Peter O.; de Freitas Pacheco, José; Weber, Fridolin; Bodmann, Benno; Hadjimichef, Dimiter; Naysinger, Geovane; Netz-Marzola, Marcelo; Razeira, Moisés, The accelerating universe in a noncommutative analytically continued foliated quantum gravity, published in Classical and Quantum Gravity, Volume 41, Issue 24 on December 2024.
Based on an analytically continued Riemannian foliated quantum gravity super-Hamiltonian, known as branch cut quantum gravity (BCQG) we propose a novel approach to investigating the effects of noncommutative geometry on a minisuperspace of variables, influencing the acceleration behavior of the Universe's wave function and the cosmic scale factor. Noncommutativity is introduced through a deformation of the conventional Poisson algebra, enhanced with a symplectic metric. The resulting symplectic manifold provides a natural setting that enables an isomorphism between canonically conjugate dual vector spaces, spanning the BCQG cosmic scale factor and its complementary quantum counterpart. Using this formulation, we describe the dynamic evolution of the Universe's wave function, the cosmic scale factor, and its complementary quantum image. Our results strongly suggest that the noncommutative algebra induces late-time accelerated growth of the wave function, the Universe's scale factor, and its complementary quantum counterpart, offering a new perspective on explaining the accelerating cosmic expansion rate and the inflationary period. In contrast to the inflationary model, where inflation requires a remarkably fine-tuned set of initial conditions in a patch of the Universe, analytically continued non-commutative foliated quantum gravity captures short and long scales, driving the evolutionary dynamics of the Universe through a reconfiguration of the primordial cosmic content of matter and energy. This reconfiguration is encapsulated into a quantum field potential, which leads to the generation of relic gravitational waves, a topic for future investigation. Graphical representations and contour plots indicate a characteristic torsion (or twist) deformation of spacetime geometry. This result introduces new speculative elements regarding the reconfiguration of matter and energy as a driver of spacetime torsion deformation, generating relic gravitational waves and serving as an alternative topological mechanism for the Universe's acceleration. However, these assumptions require further investigation.
Alfano, Anna Chiara; Luongo, Orlando; Muccino, Marco, Cosmological constraints from calibrated Ep - E iso gamma-ray burst correlation by using DESI 2024 data release, published in Journal of Cosmology and Astroparticle Physics, Volume 2024, Issue 12 on December 2024.
Recent outcomes by the DESI Collaboration have shed light on a possible slightly evolving dark energy, challenging the standard ΛCDM paradigm. To better understand dark energy nature, high-redshift observations like gamma-ray burst data become essential for mapping the universe expansion history, provided they are calibrated with other probes. To this aim, we calibrate the Ep - Eiso (or Amati) correlation through model-independent Bézier interpolations of the updated Hubble rate and the novel DESI data sets. More precisely, we provide two Bézier calibrations: i) handling the entire DESI sample, and ii) excluding the point at zeff = 0.51, criticized by the recent literature. In both the two options, we let the comoving sound horizon at the drag epoch, rd, vary in the range rd∈ [138, 156] Mpc. The Planck value is also explored for comparison. By means of the so-calibrated gamma-ray bursts, we thus constrain three dark energy frameworks, namely the standard ΛCDM, the ω 0CDM and the ω 0 ω 1CDM models, in both spatially flat and non-flat universes. To do so, we worked out Monte Carlo Markov chain analyses, making use of the Metropolis-Hastings algorithm. Further, we adopt model selection criteria to check the statistically preferred cosmological model finding a preference towards the concordance paradigm with a zero curvature parameter. Nonetheless, the criteria also show a weak preference towards the non-flat ΛCDM and the flat ω 0CDM scenario, leaving open to the possibility of such models as alternatives to the flat concordance paradigm. Finally, we compared the constraints got from the prompt emission Ep - E iso correlation with those from the prompt-afterglow emission LX - TX - Lp correlation.
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 December 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 ( ≥ 5 σ) 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, Multi-wavelength study of OT 081: broadband modelling of a transitional blazar, published in Monthly Notices of the Royal Astronomical Society on December 2024.
OT 081 is a well-known, luminous blazar that is remarkably variable in many energy bands. We present the first broadband study of the source which includes very-high-energy (VHE, E >100 GeV) γ-ray data taken by the MAGIC and H.E.S.S. imaging Cherenkov telescopes. The discovery of VHE γ-ray emission happened during a high state of γ-ray activity in July 2016, observed by many instruments from radio to VHE γ-rays. We identify four states of activity of the source, one of which includes VHE γ-ray emission. Variability in the VHE domain is found on daily timescales. The intrinsic VHE spectrum can be described by a power-law with index 3.27 ± 0.44stat ± 0.15sys (MAGIC) and 3.39 ± 0.58stat ± 0.64sys (H.E.S.S.) in the energy range of 55-300 GeV and 120-500 GeV, respectively. The broadband emission cannot be sucessfully reproduced by a simple one-zone synchrotron self-Compton model. Instead, an additional external Compton component is required. We test a lepto-hadronic model that reproduces the dataset well and a proton-synchrotron dominated model that requires an extreme proton luminosity. Emission models that are able to successfully represent the data place the emitting region well outside of the Broad Line Region (BLR) to a location at which the radiative environment is dominated by the infrared thermal radiation field of the dusty torus. In the scenario described by this flaring activity, the source appears to be an FSRQ, in contrast with past categorizations. This suggests that the source can be considered to be a transitional blazar, intermediate between BL Lac and FSRQ objects.
Vasini, A.; Spitoni, E.; Matteucci, F.; Cescutti, G.; Della Valle, M., Tracing the Milky Way spiral arms with 26Al: The role of nova systems in the 2D distribution of 26Al, published in Astronomy & Astrophysics, Volume 693 on January 2025.
Context. Massive stars are one of the most important and investigated astrophysical production sites of 26Al, a short-lived radioisotope with an ~1 Myr half-life. Its short lifetime prevents us from observing its complete chemical history, and only the 26Al that was recently produced by massive stars can be observed. Hence, it is considered a tracer of star formation rate (SFR). However, important contributions to 26Al come from nova systems that pollute the interstellar medium with a large delay, thus partly erasing the correlation between 26Al and SFR. Aims. In this work, we aim to describe the 2D distribution of the mass of 26Al as well as that of massive stars and nova systems in the Milky Way (MW), to investigate their relative contributions to the production of 26Al. Methods. We used a detailed 2D chemical evolution model where the SFR is azimuthally dependent and is required to reproduce the spiral arm pattern observed in the MW. We tested two different models, one where the 26Al comes from massive stars and novae, and one with massive stars only. We then compared the predictions to the ~2 M⊙ of 26Al mass observed by the surveys of the Compton Telescope (COMPTEL) and International Gamma-Ray Laboratory (INTEGRAI). Results. The results show that novae do not trace SFR and, in the solar vicinity, they concentrate in its minima. The effect of novae on the map of the 26Al mass consists in damping the spiral pattern by a factor of five. Regarding the nucleosynthesis, we find that ~75% of the 26Al is produced by novae and the ~25% by massive stars. Conclusions. We conclude that novae cannot be neglected as 26Al producers since the observations can only be reproduced by including their contribution. Moreover, we suggest that bulge novae should eject around six times more material than the disc ones to well reproduce the observed mass of 26Al.
Zhang, S. R.; Rueda Hernandez, J. A.; Negreiros, R., Can the Central Compact Object in HESS J1731–347 Be Indeed the Lightest Neutron Star Observed?, published in The Astrophysical Journal, Volume 978, Issue 1, on January 2025.
The exceptionally low mass of for the central compact object (CCO) XMMU J173203.3–344518 (XMMU J1732) in the supernova remnant (SNR) HESS J1731–347 challenges standard neutron star (NS) formation models. The nearby post–asymptotic giant branch star IRAS 17287–3443 (≈0.6M⊙), also within the SNR, enriches the scenario. To address this puzzle, we advance the possibility that the gravitational collapse of a rotating presupernova (SN) iron core (≈1.2M⊙) could result in a low-mass NS. We show that angular momentum conservation during the collapse of an iron core rotating at ≈45% of the Keplerian limit results in a mass loss of ≈0.3M⊙, producing a stable newborn NS of ≈0.9M⊙. Considering the possible spin-down, this indicates that the NS is now slowly rotating, thus fulfilling the observed mass–radius relation. Additionally, the NS's surface temperature (≈2 × 106 K) aligns with canonical thermal evolution for its ≈4.5 kyr age. We propose the pre-SN star, likely an ultrastripped core of ≈4.2M⊙, formed a tidally locked binary with IRAS 17287–3443, with a 1.43 day orbital period. The SN led to a ≈3M⊙ mass loss, imparting a kick velocity ≲670 km s‑1, which disrupted the binary. This scenario explains the observed 0.3 pc offset between XMMU J1732 and IRAS 17287–3443 and supports the possibility of CCOs forming in binaries, with rotation playing a key role in core collapse, and the CCO XMMU J1732 being the lightest NS ever observed.
Li, Jie; Lv, Hongkui; Liu, Yang; Huang, Jiajun; Wang, Yu; Lin, Wenbin, Application of Machine Learning to Background Rejection in Very-high-energy Gamma-Ray Observation, published in The Astrophysical Journal Supplement Series, Volume 276, Issue 1 on January 2025.
Identifying gamma rays and rejecting the background of cosmic-ray hadrons are crucial for very-high-energy gamma-ray observations and relevant scientific research. Based on the simulated data from the square kilometer array (KM2A) of LHAASO, eight high-level features were extracted for the gamma/hadron classification. Machine learning (ML) models, including logistic regression, support vector machines, decision trees, random forests, XGBoost, CatBoost, and deep neural networks (DNN) were constructed and trained using data sets of four energy bands ranging from 1012 to 1016 eV, and finally fused using the stacking ensemble algorithm. To comprehensively assess the classification ability of each model, the accuracy, F1 score, precision, recall, and area under the curve value of the receiver operating characteristic curve were used. The results show that the ML methods have a significant improvement on particle classification in LHAASO-KM2A, particularly in the low-energy range. Among these methods, XGBoost, CatBoost, and DNN demonstrate stronger classification capabilities than decision trees and random forests, while the fusion model exhibits the best discriminatory ability. The ML methods provide a useful and alternative method for gamma/hadron identification. The codes used in this paper are available at Zenodo at doi:10.5281/zenodo.13623261.
Carloni, Youri; Luongo, Orlando; Muccino, Marco, Does dark energy really revive using DESI 2024 data?,Physical Review D, Volume 111, Issue 2 on January 2025.
We investigate the impact of the Dark Energy Spectroscopic Instrument (DESI) 2024 data on dark energy scenarios. We thus analyze three typologies of models, the first in which the cosmic speedup is related to thermodynamics and the second associated with Taylor expansions of the barotropic factor, whereas the third is based on ad hoc dark energy parametrizations. In this respect, we first work at the background, inferring a posteriori kinematic quantities associated with each model. Afterward, we obtain early-time predictions, computing departures on the growth evolution with respect to the model that better fits DESI data. We find that—depending on the combination of catalogs hereby considered, but independently from whether a debated data point placed at z=0.51 is removed or not—the best model to fit data is not the Chevallier-Polarski-Linder (CPL) parametrization but rather a more complicated log-corrected dark energy contribution or the ΛCDM model, indicating that the possible tension between the concordance paradigm and the CPL model can be severely alleviated. We conclude that future data points will be essential to clarify whether dynamical dark energy is really in tension with the ΛCDM model.
Pace, C. M., The Gravitational Potential and the Gravitational Force According to the Correct Reissner-Nordstrøm, Kerr and Kerr-Newman Metrics, published in Journal of Modern Physics, Vol.16 No.1 on January 2025.
In a recent article, we have corrected the traditional derivation of the Schwarzschild metric, thus obtaining the formulation of the correct Schwarzschild metric, which is different from the traditional Schwarzschild metric. In this article, by starting from this correct Schwarzschild metric, we obtain the formulas of the correct gravitational potential and of the correct gravitational force in the case described by this metric. 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.
Pace, C. M., The Gravitational Potential and the Gravitational Force According to the Correct Schwarzschild Metric, published in Journal of Modern Physics, Vol.15, No.12 on November 2024.
In a recent article, we have corrected the traditional derivation of the Schwarzschild metric, thus obtaining the formulation of the correct Schwarzschild metric, which is different from the traditional Schwarzschild metric. In this article, by starting from this correct Schwarzschild metric, we obtain the formulas of the correct gravitational potential and of the correct gravitational force in the case described by this metric. 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.
B. Eslam Panah, Super-entropy bumblebee AdS black holes, to be published in Physics Letters B, Volume 861 on February 2025.
Motivated by the effect of the bumblebee field on thermodynamic instability in (non)extended phase space, we study the thermodynamic instability for the bumblebee AdS black holes. For this purpose, first, we evaluate the effect of the bumblebee field (or Lorentz-violating parameter) on the event horizon for AdS black holes. Then, in non-extended phase space, we study the effect of the bumblebee field on the heat capacity and the Helmholtz free energy to investigate the local and global thermal stability areas, respectively. Next, we extend our study on the extended phase space by seeking on stable area by using the heat capacity at constant pressure (Cp). Finally, we evaluate the super-entropy black hole condition and indicate that the bumblebee AdS black holes are super-entropy black holes when l > 0, which is consistent with the condition Cp > 0.
B. Eslam Panah, and N. Heidari, Some aspects of ModMax (A)dS black holes: Thermodynamics properties, heat engine, shadow, null geodesic and light trajectory, to be published in Journal of High Energy Astrophysics, Volume 45 on March 2025.
In this paper, we focus on the extraction of electrically charged black holes in the presence of modified Maxwell nonlinear electrodynamics and the cosmological constant, known as ModMax-(A)dS black holes. These black holes are of particular interest due to the substantial influence of the nonlinear Maxwell field (ModMax) and the cosmological constant on their properties. After obtaining exact ModMax-(A)dS black hole solutions, we proceed to study their thermodynamic properties, including conserved and thermodynamic quantities, as well as the first law of thermodynamics in a non-extended phase space. The local and global stabilities of these black holes are then assessed. Local stability is evaluated by examining the heat capacity while determining global stability involves calculating the Helmholtz free energy. Then, we investigate the heat engine of ModMax (A)dS black holes, considering the effects of the ModMax parameter and the cosmological constant on all quantities. Moreover, we explore the imprint of ModMax (A)dS black hole parameters on the critical orbits and shadow radius size, the results are compared with EHT observational data of the Sagittarius A* black holes. Lastly, the null geodesics and light trajectory are discussed in the presence of the ModMax theory.
Ottoni, Tulio; Coelho, Jaziel, G.; de Lima, Rafael C. R.; Pereira, Jonas P.; Rueda, Jorge A., X-ray pulsed light curves of highly compact neutron stars as probes of scalar–tensor theories of gravity, published in The European Physical Journal C, Volume 84, Issue 12 on December 2024.
The strong gravitational potential of neutron stars (NSs) makes them ideal astrophysical objects for testing extreme gravity phenomena. We explore the potential of NS X-ray pulsed light curve observations to probe deviations from general relativity (GR) within the scalar–tensor theory (STT) of gravity framework. We compute the flux from a single, circular, finite-size hot spot, accounting for light bending, Shapiro time delay, and Doppler effect. We focus on the high-compactness regime, i.e., close to the critical GR value GM/(c2R)=0.284, over which multiple images of the spot appear and impact crucially the light curves. Our investigation is motivated by the increased sensitivity of the pulse to the scalar charge of the spacetime in such high compactness regimes, making these systems exceptionally suitable for scrutinizing deviations from GR, notably phenomena such as spontaneous scalarization, as predicted by STT. We find significant differences in NS observables, e.g., the flux of a single spot can differ up to 80% with respect to GR. Additionally, reasonable choices for the STT parameters that satisfy astrophysical constraints lead to changes in the NS radius relative to GR of up to approximately 10%. Consequently, scalar parameters might be better constrained when uncertainties in NS radii decrease, where this could occur with the advent of next-generation gravitational wave detectors, such as the Einstein Telescope and LISA, as well as future electromagnetic missions like eXTP and ATHENA. Thus, our findings suggest that accurate X-ray data of the NS surface emission, jointly with refined theoretical models, could constrain STTs.
Luongo, Orlando; Muccino, Marco; Dark energy reconstructions combining baryonic acoustic oscillation data with galaxy clusters and intermediate-redshift catalogs, published in Astronomy & Astrophysics, Volume 693 on January 2025.
Context. Cosmological parameters and dark energy (DE) behavior are generally constrained assuming a priori models. Aims. We work out a model-independent reconstruction to bind the key cosmological quantities and the DE evolution. Methods. Through the model-independent Bézier interpolation method, we reconstructed the Hubble rate from the observational Hubble data and derived analytic expressions for the distances of galaxy clusters, type Ia supernovae, and uncorrelated baryonic acoustic oscillation (BAO) data. In view of the discrepancy between Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) BAO data, they were kept separate in two distinct analyses. Correlated BAO data were employed to break the baryonic–dark matter degeneracy. All these interpolations enable us to single out and reconstruct the DE behavior with the redshift z in a totally model-independent way. Results. In both analyses, with SDSS-BAO or DESI-BAO datasets, the constraints agree at a 1–σ confidence level (CL) with the flat ΛCDM model. The Hubble constant tension appears solved in favor of the Planck satellite value. The reconstructed DE behavior exhibits deviations at small z (> 1–σ CL), but agrees (< 1–σ CL) with the cosmological constant paradigm at larger z. Conclusions. Our method hints at a slowly evolving DE, consistent with a cosmological constant at early times.
MAGIC collaboration, Cosmic-ray acceleration and escape from supernova remnant W44 as probed by Fermi-LAT and MAGIC, Astronomy & Astrophysics, Volume 693, January 2025.
Context. The supernova remnant (SNR) W44 and its surroundings are a prime target for studying the acceleration of cosmic rays (CRs). Several previous studies established an extended gamma-ray emission that is set apart from the radio shell of W44. This emission is thought to originate from escaped high-energy CRs that interact with a surrounding dense molecular cloud complex. Aims. We present a detailed analysis of Fermi-LAT data with an emphasis on the spatial and spectral properties of W44 and its surroundings. We also report the results of the observations performed with the MAGIC telescopes of the northwestern region of W44. Finally, we present an interpretation model to explain the gamma-ray emission of the SNR and its surroundings. Methods. We first performed a detailed spatial analysis of 12 years of Fermi-LAT data at energies above 1 GeV, in order to exploit the better angular resolution, while we set a threshold of 100 MeV for the spectral analysis. We performed a likelihood analysis of 174 hours of MAGIC data above 130 GeV using the spatial information obtained with Fermi-LAT. Results. The combined spectra of Fermi-LAT and MAGIC, extending from 100 MeV to several TeV, were used to derive constraints on the escape of CRs. Using a time-dependent model to describe the particle acceleration and escape from the SNR, we show that the maximum energy of the accelerated particles has to be ≃40 GeV. However, our gamma-ray data suggest that a small number of lower-energy particles also needs to escape. We propose a novel model, the broken-shock scenario, to account for this effect and explain the gamma-ray emission.
Wang, Chen-Wei; Tan, Wen-Jun; Xiong, Shao-Lin; Yi, Shu-Xu; Moradi, Rahim; Li, Bing; Zhang, Zhen; Wang, Yu; Meng, Yan-Zhi; Wu, Bo-Bing; Liu, Jia-Cong; Wang, Yue; Xie, Sheng-Lun; Xue, Wang-Chen; Yu, Zheng-Hang; Zhang, Peng; Zhang, Wen-Long; Zhang, Yan-Qiu; Zheng, Chao, A Subclass of Gamma-Ray Burst Originating from Compact Binary Merger, published in The Astrophysical Journal, Volume 979, Issue 1 on January 2025.
Type I gamma-ray bursts (GRBs) are believed to originate from compact binary mergers usually with a duration of main emission less than 2 s. However, recent observations of GRB 211211A and GRB 230307A indicate that some merger-origin GRBs could last much longer. Since they show strikingly similar properties (indicating a common mechanism), which are different from the classic "long"-short burst (e.g., GRB 060614), we find they form an interesting subclass of type I GRBs, and we suggest to name them as type IL GRB. We find that the prompt emission of type IL GRB is composed of three episodes: (1) a precursor followed by a short quiescent (or weak emission) period, (2) a long-duration main emission, and (3) an extended emission. With this burst pattern, a good candidate, GRB 170228A, was found in the Fermi/Gamma-ray Burst Monitor archive data. Temporal and spectral analyses indeed show that GRB 170228A falls in the same group with GRB 211211A and GRB 230307A in many diagnostic figures. Thus, this burst pattern could be a good reference for rapidly identifying type IL GRBs and very helpful for conducting low-latency follow-up observation. We estimated the occurrence rate and discussed the physical origins and implications for the three emission episodes of type IL GRBs. Our analysis suggests the premerger precursor model, especially the magnetar super flare model, is more favored for type IL GRBs. More observations in multiwavelength and multimessenger are required to deepen our understanding of this subclass of GRB.
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.
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