Pub Date : 2026-02-01Epub Date: 2025-09-15DOI: 10.1016/j.jheap.2025.100464
J.A. Rueda , R. Ruffini , Yu Wang
We model the short gamma-ray bursts (GRB) 090510 as the product of a magnetized neutron star (NS) binary merger. Accounting for the NS critical mass constraint given by the mass of PSR J0952–0607, we infer that GRB 090510 was a highly-magnetized NS-NS merger that left as remnant a Kerr black hole (BH) of with a low-mass accretion disk. The gamma-ray precursor is powered by the magnetic energy released during the merger of the NSs. The prompt emission originates at the transparency of an ultra-relativistic pair-plasma produced by the overcritical electric field induced by the rotating strong magnetic field around the merged object before it reaches the critical mass, the GeV emission by the extractable energy of the newborn BH, and the X-ray afterglow by accretion onto it. We derive the masses of the merging NSs, their magnetic fields, the BH mass, spin, and irreducible mass, the strength of the magnetic field, the disk mass, and obtain an estimate of the gravitational-wave emission during the merger phase preceding the prompt short GRB emission. The inferred parameters agree with up-to-date numerical relativity simulations, confirming that strong magnetic fields above 1014 G develop in NS-NS mergers and that mergers leading to a central BH remnant have low-mass disks of . We also advance the possibility that quasi-period oscillations of tens of Hz of frequency due to Lense-Thirring precession of the matter surrounding the merged object before BH formation can explain the successive spikes following the prompt emission peak.
{"title":"Short GRB 090510: A magnetized neutron star binary merger leading to a black hole","authors":"J.A. Rueda , R. Ruffini , Yu Wang","doi":"10.1016/j.jheap.2025.100464","DOIUrl":"10.1016/j.jheap.2025.100464","url":null,"abstract":"<div><div>We model the short gamma-ray bursts (GRB) 090510 as the product of a magnetized neutron star (NS) binary merger. Accounting for the NS critical mass constraint given by the mass of PSR J0952–0607, we infer that GRB 090510 was a highly-magnetized NS-NS merger that left as remnant a Kerr black hole (BH) of <span><math><mn>2.4</mn><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span> with a low-mass accretion disk. The gamma-ray precursor is powered by the magnetic energy released during the merger of the NSs. The prompt emission originates at the transparency of an ultra-relativistic <span><math><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></math></span> pair-plasma produced by the overcritical electric field induced by the rotating strong magnetic field around the merged object before it reaches the critical mass, the GeV emission by the extractable energy of the newborn BH, and the X-ray afterglow by accretion onto it. We derive the masses of the merging NSs, their magnetic fields, the BH mass, spin, and irreducible mass, the strength of the magnetic field, the disk mass, and obtain an estimate of the gravitational-wave emission during the merger phase preceding the prompt short GRB emission. The inferred parameters agree with up-to-date numerical relativity simulations, confirming that strong magnetic fields above 10<sup>14</sup> G develop in NS-NS mergers and that mergers leading to a central BH remnant have low-mass disks of <span><math><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>. We also advance the possibility that quasi-period oscillations of tens of Hz of frequency due to Lense-Thirring precession of the matter surrounding the merged object before BH formation can explain the successive spikes following the prompt emission peak.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100464"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-10-03DOI: 10.1016/j.jheap.2025.100491
L.M. Becerra , F. Cipolletta , A. Drago , M. Guerrini , A. Lavagno , G. Pagliara , J.A. Rueda
Strange quark stars (SQSs), namely compact stars entirely composed of deconfined quark matter, are characterized by similar masses and compactness to neutron stars (NSs) and have been theoretically proposed to exist in the Universe since the 1970s. However, multiwavelength observations of compact stars in the last 50 years have not yet led to an unambiguous SQS identification. This article explores whether SQSs could form in the supernova (SN) explosion of an evolved star (e.g., carbon-oxygen, or Wolf-Rayet) occurring in a binary with the companion being a neutron star (NS). The collapse of the iron core of the evolved star generates a newborn NS and the SN explosion. Part of the ejected matter accretes onto the NS companion as well as onto the newborn NS via matter fallback. The accretion occurs at hypercritical (highly super-Eddington) rates, transferring mass and angular momentum to the stars. We present numerical simulations of this scenario and demonstrate that the density increase in the NS interiors during the accretion process may induce quark matter deconfinement, suggesting the possibility of SQS formation. We discuss the astrophysical conditions under which such a transition may occur and possible consequences.
{"title":"On the formation of strange quark stars from supernova in compact binaries","authors":"L.M. Becerra , F. Cipolletta , A. Drago , M. Guerrini , A. Lavagno , G. Pagliara , J.A. Rueda","doi":"10.1016/j.jheap.2025.100491","DOIUrl":"10.1016/j.jheap.2025.100491","url":null,"abstract":"<div><div>Strange quark stars (SQSs), namely compact stars entirely composed of deconfined quark matter, are characterized by similar masses and compactness to neutron stars (NSs) and have been theoretically proposed to exist in the Universe since the 1970s. However, multiwavelength observations of compact stars in the last 50 years have not yet led to an unambiguous SQS identification. This article explores whether SQSs could form in the supernova (SN) explosion of an evolved star (e.g., carbon-oxygen, or Wolf-Rayet) occurring in a binary with the companion being a neutron star (NS). The collapse of the iron core of the evolved star generates a newborn NS and the SN explosion. Part of the ejected matter accretes onto the NS companion as well as onto the newborn NS via matter fallback. The accretion occurs at hypercritical (highly super-Eddington) rates, transferring mass and angular momentum to the stars. We present numerical simulations of this scenario and demonstrate that the density increase in the NS interiors during the accretion process may induce quark matter deconfinement, suggesting the possibility of SQS formation. We discuss the astrophysical conditions under which such a transition may occur and possible consequences.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100491"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The corrections due to perturbative quantum chromodynamics and the colour superconductivity indicate that, under the extreme conditions, strongly interacting matter can manifest unique physical behaviours. Motivated by this notion, we investigate the interior structure and properties of quark stars composed of interacting quark matter, which provides a comprehensive avenue to explore the strong interaction effects, within the framework of gravity. A unified equation of state is formulated to describe various phases of quark matter, including up-down quark matter , strange quark matter , and the Colour-Flavor Locked phase. Employing a systematic reparametrisation and rescaling, the number of degrees of freedom in the equation of state is significantly reduced. Utilising the Buchdahl-I metric ansatz and a linear functional form, , we obtain the exact solutions of the Einstein field equations in presence of the unified interacting quark matter equation of state. For the phase, we examine the properties of quark stars composed of up-down quark matter. For the and CFL phases, we incorporate the effects of a finite strange quark mass . The TOV equations are solved to determine the maximum mass-radius relations for each phase. Our results indicate that the model satisfies key physical criteria, including causality, energy conditions, and stability requirements, ensuring the viability of the configurations. Furthermore, the predicted radii for different compact stars align well with observational data. The study highlights that quark stars composed of interacting quark matter within the gravity framework provide a robust and physically consistent stellar model across all considered phases.
{"title":"Interacting quark matter and extended Symmetric Teleparallel Equivalent of General Relativity: A new paradigm in exploring the properties of quark stars","authors":"Debadri Bhattacharjee, Koushik Ballav Goswami, Pradip Kumar Chattopadhyay","doi":"10.1016/j.jheap.2025.100509","DOIUrl":"10.1016/j.jheap.2025.100509","url":null,"abstract":"<div><div>The corrections due to perturbative quantum chromodynamics and the colour superconductivity indicate that, under the extreme conditions, strongly interacting matter can manifest unique physical behaviours. Motivated by this notion, we investigate the interior structure and properties of quark stars composed of interacting quark matter, which provides a comprehensive avenue to explore the strong interaction effects, within the framework of <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity. A unified equation of state is formulated to describe various phases of quark matter, including up-down quark matter <span><math><mo>(</mo><mn>2</mn><mi>S</mi><mi>C</mi><mo>)</mo></math></span>, strange quark matter <span><math><mo>(</mo><mn>2</mn><mi>S</mi><mi>C</mi><mo>+</mo><mi>s</mi><mo>)</mo></math></span>, and the Colour-Flavor Locked <span><math><mo>(</mo><mi>C</mi><mi>F</mi><mi>L</mi><mo>)</mo></math></span> phase. Employing a systematic reparametrisation and rescaling, the number of degrees of freedom in the equation of state is significantly reduced. Utilising the Buchdahl-I metric ansatz and a linear <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> functional form, <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo><mo>=</mo><msub><mrow><mi>α</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><msub><mrow><mi>α</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>Q</mi></math></span>, we obtain the exact solutions of the Einstein field equations in presence of the unified interacting quark matter equation of state. For the <span><math><mn>2</mn><mi>S</mi><mi>C</mi></math></span> phase, we examine the properties of quark stars composed of up-down quark matter. For the <span><math><mo>(</mo><mn>2</mn><mi>S</mi><mi>C</mi><mo>+</mo><mi>s</mi><mo>)</mo></math></span> and <em>CFL</em> phases, we incorporate the effects of a finite strange quark mass <span><math><mo>(</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>≠</mo><mn>0</mn><mo>)</mo></math></span>. The TOV equations are solved to determine the maximum mass-radius relations for each phase. Our results indicate that the model satisfies key physical criteria, including causality, energy conditions, and stability requirements, ensuring the viability of the configurations. Furthermore, the predicted radii for different compact stars align well with observational data. The study highlights that quark stars composed of interacting quark matter within the <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity framework provide a robust and physically consistent stellar model across all considered phases.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100509"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-17DOI: 10.1016/j.jheap.2025.100511
Khawaja T. Tasneem , M. Umair Shahzad , Nusrat Perveen , Kamal M. Othman , Abdulfattah Noorwali , Esam Y.O. Zafar
Blue straggler stars (BSSs) are intriguing anomalies in Globular Clusters (GCs) that challenge conventional stellar evolution models by appearing both younger and more luminous than their cluster counterparts. Accurately estimating their populations is crucial for understanding their formation mechanisms and the dynamic evolution of GCs. However, traditional photometric and spectroscopic methods are constrained by observational biases and computational limitations. In this study, we propose a machine learning (ML) framework to predict BSS populations in GCs using simulated data from the Monte Carlo Cluster simulator (MOCCA) Survey Database 1, which models 12 Gyr of GC evolution. We train three ML algorithms: XGBoost, Gradient Boosting, and Random Forest Regression on 12 dynamical and structural cluster properties to estimate BSS numbers. Model performance is assessed by utilizing normalized root mean square error (nRMSE), normalized mean absolute error (nMAE), and coefficient of determination (). Among the tested models, XGBoost exhibits the most accurate model (, , ), outperforming Gradient Boosting (, , ) and Random Forest Regression (, , ). Our results demonstrate that ML models can accurately predict BSS populations in real GCs, offering a robust alternative to traditional observational methods. This approach enables efficient, high-precision BSS estimation while mitigating the challenges posed by observational constraints, thereby advancing our understanding of GC stellar populations and their evolutionary pathways. Additionally, we compare our findings with literature and discover that ML outperforms conventional observational techniques by detecting noticeably more BSS in the majority of, especially in packed settings. This implies that ML is eeficient technique for examining star development and cluster dynamics and that earlier research may have understated BSS populations.
{"title":"Machine learning-based prediction of blue straggler star populations in stellar clusters","authors":"Khawaja T. Tasneem , M. Umair Shahzad , Nusrat Perveen , Kamal M. Othman , Abdulfattah Noorwali , Esam Y.O. Zafar","doi":"10.1016/j.jheap.2025.100511","DOIUrl":"10.1016/j.jheap.2025.100511","url":null,"abstract":"<div><div>Blue straggler stars (BSSs) are intriguing anomalies in Globular Clusters (GCs) that challenge conventional stellar evolution models by appearing both younger and more luminous than their cluster counterparts. Accurately estimating their populations is crucial for understanding their formation mechanisms and the dynamic evolution of GCs. However, traditional photometric and spectroscopic methods are constrained by observational biases and computational limitations. In this study, we propose a machine learning (ML) framework to predict BSS populations in GCs using simulated data from the Monte Carlo Cluster simulator (MOCCA) Survey Database 1, which models 12 Gyr of GC evolution. We train three ML algorithms: XGBoost, Gradient Boosting, and Random Forest Regression on 12 dynamical and structural cluster properties to estimate BSS numbers. Model performance is assessed by utilizing normalized root mean square error (nRMSE), normalized mean absolute error (nMAE), and coefficient of determination (<span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>). Among the tested models, XGBoost exhibits the most accurate model (<span><math><mi>n</mi><mi>R</mi><mi>M</mi><mi>S</mi><mi>E</mi><mo>=</mo><mn>0.037</mn></math></span>, <span><math><mi>n</mi><mi>M</mi><mi>A</mi><mi>E</mi><mo>=</mo><mn>0.024</mn></math></span>, <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>0.933</mn></math></span>), outperforming Gradient Boosting (<span><math><mi>n</mi><mi>R</mi><mi>M</mi><mi>S</mi><mi>E</mi><mo>=</mo><mn>0.041</mn></math></span>, <span><math><mi>n</mi><mi>M</mi><mi>A</mi><mi>E</mi><mo>=</mo><mn>0.027</mn></math></span>, <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>0.926</mn></math></span>) and Random Forest Regression (<span><math><mi>n</mi><mi>R</mi><mi>M</mi><mi>S</mi><mi>E</mi><mo>=</mo><mn>0.041</mn></math></span>, <span><math><mi>n</mi><mi>M</mi><mi>A</mi><mi>E</mi><mo>=</mo><mn>0.026</mn></math></span>, <span><math><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>0.927</mn></math></span>). Our results demonstrate that ML models can accurately predict BSS populations in real GCs, offering a robust alternative to traditional observational methods. This approach enables efficient, high-precision BSS estimation while mitigating the challenges posed by observational constraints, thereby advancing our understanding of GC stellar populations and their evolutionary pathways. Additionally, we compare our findings with literature and discover that ML outperforms conventional observational techniques by detecting noticeably more BSS in the majority of, especially in packed settings. This implies that ML is eeficient technique for examining star development and cluster dynamics and that earlier research may have understated BSS populations.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100511"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-04DOI: 10.1016/j.jheap.2025.100505
Sílvia P. Nunes , José D.V. Arbañil , Juan M.Z. Pretel , Sérgio B. Duarte
White Dwarfs (WDs), the final evolutionary stage of most stars, are frequently modeled considering only a dense plasma matter. However, their potential interaction with dark matter (DM), especially in galactic halos where DM is expected to be prevalent, may lead to significant consequences. This work proposes a novel EoS (EoS) that consistently incorporates both hot dense plasma and cold dark matter (CDM) contributions in hot WDs. The hot dense plasma EoS is extended to include thermal and radiative contributions. At the same time, the CDM component is modeled as a linear fluid, with the coupling constant α determined self-consistently within the star. A smooth phase transition between hot dense plasma and CDM regimes is introduced via a hyperbolic mixing function that depends on local energy density and stellar temperature. Our results show that the inclusion of CDM leads to an increase in the WD radius by approximately 12% and a total mass enhancement of 0.7%, compared to standard hot WD models without lattice effects. These results highlight the importance of considering CDM in stellar modeling and suggest that WDs may serve as indirect probes for the astrophysical properties of dark matter.
{"title":"Dark matter in White Dwarfs: Implications for their structure","authors":"Sílvia P. Nunes , José D.V. Arbañil , Juan M.Z. Pretel , Sérgio B. Duarte","doi":"10.1016/j.jheap.2025.100505","DOIUrl":"10.1016/j.jheap.2025.100505","url":null,"abstract":"<div><div>White Dwarfs (WDs), the final evolutionary stage of most stars, are frequently modeled considering only a dense plasma matter. However, their potential interaction with dark matter (DM), especially in galactic halos where DM is expected to be prevalent, may lead to significant consequences. This work proposes a novel EoS (EoS) that consistently incorporates both hot dense plasma and cold dark matter (CDM) contributions in hot WDs. The hot dense plasma EoS is extended to include thermal and radiative contributions. At the same time, the CDM component is modeled as a linear fluid, with the coupling constant <em>α</em> determined self-consistently within the star. A smooth phase transition between hot dense plasma and CDM regimes is introduced via a hyperbolic mixing function that depends on local energy density and stellar temperature. Our results show that the inclusion of CDM leads to an increase in the WD radius by approximately 12% and a total mass enhancement of 0.7%, compared to standard hot WD models without lattice effects. These results highlight the importance of considering CDM in stellar modeling and suggest that WDs may serve as indirect probes for the astrophysical properties of dark matter.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100505"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145466543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-10-24DOI: 10.1016/j.jheap.2025.100500
This study presents a search for magnetic monopoles using the full ANTARES dataset collected over 14 years (2008–2022). The interaction of monopoles with matter was modeled according to the Kazama, Yang and Goldhaber cross-section, and dedicated reconstruction strategies were applied to probe velocities both above and below the Cherenkov threshold. No signal consistent with monopoles was found. We derive 90% C.L. upper limits on the flux of relativistic monopoles at the level of , improving upon previous ANTARES results and confirming those obtained by IceCube and other neutrino telescopes. These results constitute the final contribution of ANTARES to the search for magnetic monopoles.
{"title":"Search for magnetic monopoles with the complete ANTARES dataset","authors":"","doi":"10.1016/j.jheap.2025.100500","DOIUrl":"10.1016/j.jheap.2025.100500","url":null,"abstract":"<div><div>This study presents a search for magnetic monopoles using the full ANTARES dataset collected over 14 years (2008–2022). The interaction of monopoles with matter was modeled according to the Kazama, Yang and Goldhaber cross-section, and dedicated reconstruction strategies were applied to probe velocities both above and below the Cherenkov threshold. No signal consistent with monopoles was found. We derive 90% C.L. upper limits on the flux of relativistic monopoles at the level of <span><math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>18</mn></mrow></msup><mspace></mspace><mrow><mi>c</mi><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace></mspace><mi>s</mi><msup><mrow><mi>r</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, improving upon previous ANTARES results and confirming those obtained by IceCube and other neutrino telescopes. These results constitute the final contribution of ANTARES to the search for magnetic monopoles.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100500"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-09-16DOI: 10.1016/j.jheap.2025.100465
A. Bonollo , P. Esposito , A. Giuliani , P. Caraveo , G. Galanti , S. Crestan , M. Rigoselli , S. Mereghetti
The term PeVatron designates astrophysical objects capable of accelerating particles to PeV energies (1 PeV = 1015 eV). Their nature and particle acceleration mechanisms are uncertain, but ultra-high-energy gamma rays (>100 TeV) are produced when particles accelerated by either leptonic and hadronic PeVatrons interact with the surrounding medium or radiation fields. The atmospheric air shower observatory LHAASO detected photons with energies above 100 TeV from 43 sources in the Galactic Plane, proving the existence of PeVatrons within the Milky Way. In particular, one of the detections was a 1.4 PeV photon in spatial correspondence with Cygnus OB2, providing a strong hint that young massive stellar clusters (YMSCs) can act as PeVatrons.
The next-generation ground-based Cherenkov telescopes will have unprecedented energy and angular resolution. Therefore, they will be able to resolve spatially YMSCs better than LHAASO. We focused on a sample of 5 YMSCs and their environments visible from either hemisphere with the CTAO or ASTRI Mini-Array. We modelled the secondary gamma-ray emission above 1 TeV and simulated observations of all sources. We devised methods for classifying YMSCs that could be detected as unidentified extended TeV sources and estimate the observational time needed to distinguish the morphology of different classes of sources.
We study the morphology of the sources in our sample in order to identify their main features. We simulated observations of all sources with the instrument response function (IRF) of CTAO or ASTRI Mini-Array. We compare their emission distribution to the one of the TeV halos observed by HAWC. We parametrize their radial profiles in order to develop methodologies to classify them and to distinguish YMSCs from TeV halos based on their morphology. We expect some feature, such as the emission peak, to be key in differentiating between the two classes of objects. We then test them on a sample of sources of the first LHAASO catalogue.
{"title":"Morphology of young massive stellar clusters with next-generation IACTs","authors":"A. Bonollo , P. Esposito , A. Giuliani , P. Caraveo , G. Galanti , S. Crestan , M. Rigoselli , S. Mereghetti","doi":"10.1016/j.jheap.2025.100465","DOIUrl":"10.1016/j.jheap.2025.100465","url":null,"abstract":"<div><div>The term PeVatron designates astrophysical objects capable of accelerating particles to PeV energies (1 PeV = 10<sup>15</sup> eV). Their nature and particle acceleration mechanisms are uncertain, but ultra-high-energy gamma rays (>100 TeV) are produced when particles accelerated by either leptonic and hadronic PeVatrons interact with the surrounding medium or radiation fields. The atmospheric air shower observatory LHAASO detected photons with energies above 100 TeV from 43 sources in the Galactic Plane, proving the existence of PeVatrons within the Milky Way. In particular, one of the detections was a 1.4 PeV photon in spatial correspondence with Cygnus OB2, providing a strong hint that young massive stellar clusters (YMSCs) can act as PeVatrons.</div><div>The next-generation ground-based Cherenkov telescopes will have unprecedented energy and angular resolution. Therefore, they will be able to resolve spatially YMSCs better than LHAASO. We focused on a sample of 5 YMSCs and their environments visible from either hemisphere with the CTAO or ASTRI Mini-Array. We modelled the secondary gamma-ray emission above 1 TeV and simulated observations of all sources. We devised methods for classifying YMSCs that could be detected as unidentified extended TeV sources and estimate the observational time needed to distinguish the morphology of different classes of sources.</div><div>We study the morphology of the sources in our sample in order to identify their main features. We simulated observations of all sources with the instrument response function (IRF) of CTAO or ASTRI Mini-Array. We compare their emission distribution to the one of the TeV halos observed by HAWC. We parametrize their radial profiles in order to develop methodologies to classify them and to distinguish YMSCs from TeV halos based on their morphology. We expect some feature, such as the emission peak, to be key in differentiating between the two classes of objects. We then test them on a sample of sources of the first LHAASO catalogue.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100465"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-11DOI: 10.1016/j.jheap.2025.100507
Himanshu Chaudhary , Salvatore Capozziello , Subhrat Praharaj , Shibesh Kumar Jas Pacif , G. Mustafa
<div><div>We present strong evidences for dynamical dark energy challenging the ΛCDM model. Several dark energy models are explored, including <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM, logarithmic, Exponential, JBP, and BA, along with non-flat cosmological models accounting also for potential spatial curvature different from zero. Through our analysis, we find evidences supporting a flat Universe (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>≈</mo><mn>0</mn></math></span>). Using the Metropolis-Hastings Markov Chain Monte Carlo algorithm, we analyze observational data from Baryon Acoustic Oscillations of DESI DR2, Type Ia Supernovae, and Compressed CMB likelihood to constrain the parameters of these models. Our findings provide strong evidences that <span><math><mi>ω</mi><mo>≠</mo><mo>−</mo><mn>1</mn></math></span>, with deviations from the ΛCDM model favoring dynamical dark energy models characterized by the Quintom-B scenario (<span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>></mo><mo>−</mo><mn>1</mn></math></span>, <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub><mo><</mo><mn>0</mn></math></span>, and <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub><mo><</mo><mo>−</mo><mn>1</mn></math></span>). We also derive the upper bounds on <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub></math></span> using the combination of CMB and DESI DR2 data. For the ΛCDM model, we find <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.066</mn><mspace></mspace><mtext>eV</mtext></math></span>, while for <em>ω</em>CDM, it is <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.075</mn><mspace></mspace><mtext>eV</mtext></math></span>. In the oΛCDM and o<em>ω</em>CDM models, the limits are <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.263</mn><mspace></mspace><mtext>eV</mtext></math></span> and <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.520</mn><mspace></mspace><mtext>eV</mtext></math></span>, respectively. For other models, including <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM, Logarithmic, Exponential, JBP, BA, and GEDE, the upper limits range from <span><math><mo><</mo><mn>0.043</mn><mspace></mspace><mtext>eV</mtext></math></span> to <span><math><mo><</mo><mn>0.127</mn><mspace></mspace><mtext>eV</mtext></math></span>, depending on the model. Constraints on the effective number of relativistic species, <span><math><msub><mrow><mi>N</mi></mro
{"title":"Is the ΛCDM model in crisis?","authors":"Himanshu Chaudhary , Salvatore Capozziello , Subhrat Praharaj , Shibesh Kumar Jas Pacif , G. Mustafa","doi":"10.1016/j.jheap.2025.100507","DOIUrl":"10.1016/j.jheap.2025.100507","url":null,"abstract":"<div><div>We present strong evidences for dynamical dark energy challenging the ΛCDM model. Several dark energy models are explored, including <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM, logarithmic, Exponential, JBP, and BA, along with non-flat cosmological models accounting also for potential spatial curvature different from zero. Through our analysis, we find evidences supporting a flat Universe (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>≈</mo><mn>0</mn></math></span>). Using the Metropolis-Hastings Markov Chain Monte Carlo algorithm, we analyze observational data from Baryon Acoustic Oscillations of DESI DR2, Type Ia Supernovae, and Compressed CMB likelihood to constrain the parameters of these models. Our findings provide strong evidences that <span><math><mi>ω</mi><mo>≠</mo><mo>−</mo><mn>1</mn></math></span>, with deviations from the ΛCDM model favoring dynamical dark energy models characterized by the Quintom-B scenario (<span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>></mo><mo>−</mo><mn>1</mn></math></span>, <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub><mo><</mo><mn>0</mn></math></span>, and <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>+</mo><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub><mo><</mo><mo>−</mo><mn>1</mn></math></span>). We also derive the upper bounds on <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub></math></span> using the combination of CMB and DESI DR2 data. For the ΛCDM model, we find <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.066</mn><mspace></mspace><mtext>eV</mtext></math></span>, while for <em>ω</em>CDM, it is <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.075</mn><mspace></mspace><mtext>eV</mtext></math></span>. In the oΛCDM and o<em>ω</em>CDM models, the limits are <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.263</mn><mspace></mspace><mtext>eV</mtext></math></span> and <span><math><mo>∑</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>ν</mi></mrow></msub><mo><</mo><mn>0.520</mn><mspace></mspace><mtext>eV</mtext></math></span>, respectively. For other models, including <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>ω</mi></mrow><mrow><mi>a</mi></mrow></msub></math></span>CDM, Logarithmic, Exponential, JBP, BA, and GEDE, the upper limits range from <span><math><mo><</mo><mn>0.043</mn><mspace></mspace><mtext>eV</mtext></math></span> to <span><math><mo><</mo><mn>0.127</mn><mspace></mspace><mtext>eV</mtext></math></span>, depending on the model. Constraints on the effective number of relativistic species, <span><math><msub><mrow><mi>N</mi></mro","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100507"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-17DOI: 10.1016/j.jheap.2025.100510
Ido Ben-Dayan , Utkarsh Kumar , Amresh Verma
We investigate whether an Early-Universe stochastic gravitational–wave background (SGWB) can account for the common-spectrum process reported by NANOGrav, while also being consistent with current and projected CMB measurements of extra radiation. We compute the contribution of effective number of relativistic species, , for a number of Early-Universe models proposed to explain the pulsar timing array (PTA) spectrum. We demonstrate that models predicting above the CMB limit would either be excluded or require a significant additional contribution from other sources to explain the NANOGrav signal while remaining consistent with the CMB constraints. We find that current NANOGrav 15-year dataset, sensitive up to 60 nHz, gives a negligible contribution to and remains well below the present and future CMB detection threshold. However, when we project future PTA capabilities reaching upto 1 μHz, even with our conservative estimate we find that Inflation, Scalar Induced Gravitational Waves (SIGW), and metastable cosmic strings can induce a large enough for detection by the Simons Observatory.
{"title":"Disentangling the origins of the NANOGrav signal: Early Universe models and ΔNeff bounds","authors":"Ido Ben-Dayan , Utkarsh Kumar , Amresh Verma","doi":"10.1016/j.jheap.2025.100510","DOIUrl":"10.1016/j.jheap.2025.100510","url":null,"abstract":"<div><div>We investigate whether an Early-Universe stochastic gravitational–wave background (SGWB) can account for the common-spectrum process reported by NANOGrav, while also being consistent with current and projected CMB measurements of extra radiation. We compute the contribution of effective number of relativistic species, <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span>, for a number of Early-Universe models proposed to explain the pulsar timing array (PTA) spectrum. We demonstrate that models predicting <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> above the CMB limit would either be excluded or require a significant additional contribution from other sources to explain the NANOGrav signal while remaining consistent with the CMB constraints. We find that current NANOGrav 15-year dataset, sensitive up to 60 nHz, gives a negligible contribution to <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> and remains well below the present and future CMB detection threshold. However, when we project future PTA capabilities reaching upto 1 μHz, even with our conservative estimate we find that Inflation, Scalar Induced Gravitational Waves (SIGW), and metastable cosmic strings can induce a <span><math><mi>Δ</mi><msub><mrow><mi>N</mi></mrow><mrow><mi>eff</mi></mrow></msub></math></span> large enough for <span><math><mo>></mo><mn>3.5</mn><mi>σ</mi></math></span> detection by the Simons Observatory.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100510"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01Epub Date: 2025-11-17DOI: 10.1016/j.jheap.2025.100512
Mohsen Khodadi , Gaetano Lambiase , Javad T. Firouzjaee
Based on a comprehensive analysis of recent observational data—a combination of DESI DR1, Planck CMB, and Pantheon+ SN Ia—this study critically evaluates the two dark energy (DE) proposals within Harada's Conformal Killing Gravity (CKG) model. The model at question predicts either a dominant phantom-type effective DE component with EoS or a hybrid scenario combining a cosmological constant () with a subdominant fluid (around 5%) to address the Hubble tension (HT) and late-time acceleration. An analysis based on the Trans-Planckian Censorship Conjecture (TCC) demonstrates that the pure CKG fluid scenario is excluded, whereas the hybrid model remains only marginally compatible. Our Markov Chain Monte Carlo (MCMC) analysis constrains the effective DE density parameter to (68% CL), consistent with zero and ruling out the contribution required by Harada's CKG. The resulting Hubble expansion history and effective EoS are indistinguishable from those of ΛCDM. Bayesian model comparison via the Akaike Information Criterion (AIC) shows no statistical preference for CKG over ΛCDM (), disfavoring the additional complexity of the CKG model. The key output of this study is that both DE proposals in Harada's CKG are ruled out by current cosmological data, and HT remains unresolved.
{"title":"Confronting dark energy in Harada's Conformal Killing Gravity with observational data","authors":"Mohsen Khodadi , Gaetano Lambiase , Javad T. Firouzjaee","doi":"10.1016/j.jheap.2025.100512","DOIUrl":"10.1016/j.jheap.2025.100512","url":null,"abstract":"<div><div>Based on a comprehensive analysis of recent observational data—a combination of DESI DR1, Planck CMB, and Pantheon+ SN Ia—this study critically evaluates the two dark energy (DE) proposals within Harada's Conformal Killing Gravity (CKG) model. The model at question predicts either a dominant phantom-type effective DE component with EoS <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> or a hybrid scenario combining a cosmological constant (<span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>1</mn></math></span>) with a subdominant <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> fluid (around 5%) to address the Hubble tension (HT) and late-time acceleration. An analysis based on the Trans-Planckian Censorship Conjecture (TCC) demonstrates that the pure CKG fluid scenario <span><math><mi>ω</mi><mo>=</mo><mo>−</mo><mn>5</mn><mo>/</mo><mn>3</mn></math></span> is excluded, whereas the hybrid model remains only marginally compatible. Our Markov Chain Monte Carlo (MCMC) analysis constrains the effective DE density parameter to <span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>=</mo><msubsup><mrow><mn>0.009</mn></mrow><mrow><mo>−</mo><mn>0.007</mn></mrow><mrow><mo>+</mo><mn>0.006</mn></mrow></msubsup></math></span> (68% CL), consistent with zero and ruling out the <span><math><mo>∼</mo><mn>5</mn><mtext>%</mtext></math></span> contribution required by Harada's CKG. The resulting Hubble expansion history <span><math><mi>H</mi><mo>(</mo><mi>z</mi><mo>)</mo></math></span> and effective EoS <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mtext>eff</mtext></mrow></msub><mo>(</mo><mi>z</mi><mo>)</mo></math></span> are indistinguishable from those of ΛCDM. Bayesian model comparison via the Akaike Information Criterion (AIC) shows no statistical preference for CKG over ΛCDM (<span><math><mi>Δ</mi><mtext>AIC</mtext><mo>=</mo><mo>+</mo><mn>2.6</mn></math></span>), disfavoring the additional complexity of the CKG model. The key output of this study is that both DE proposals in Harada's CKG are ruled out by current cosmological data, and HT remains unresolved.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100512"},"PeriodicalIF":10.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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