Pub Date : 2025-09-25DOI: 10.1016/j.jheap.2025.100472
Athira M. Bharathan , C.S. Stalin , Sunder Sahayanathan , Blesson Mathew
X-ray polarization measurable with the imaging X-ray Polarimetry Explorer (IXPE) could constrain the long debated leptonic versus hadronic origin for the high energy component in the broad band spectral energy distribution (SED) of blazars. We report here the results from IXPE and SED modeling of PKS 2155−304 and 3C 454.3, a high and low synchrotron peaked blazar. For PKS 2155−304, from model-independent analysis, we found polarization angle = (130 ± 2.5) deg and polarization degree = (20.9 ± 1.8)% in the 2−8 keV band in agreement with spectro-polarimetric analysis. We found to vary with time and indications of it to vary between energies, suggesting that the emission regions are stratified. For 3C 454.3, we did not detect X-ray polarization in the June 2023 observation, analyzed here for the first time. The detection of X-ray polarization in PKS 2155−304 and its non-detection in 3C 454.3 is in accordance with the X-ray emission from synchrotron and inverse Compton process, respectively, operating in these sources. Further, our division of the dataset into finer time bins allows a more granular view of polarization variability. Additionally, we modeled the broadband SEDs of both the sources using data acquired quasi-simultaneously with IXPE, in the optical, UV and X-rays from Swift, AstroSat and γ-rays from Fermi. In PKS 2155−304, the observed X-ray is found to lie in the high energy tail of the synchrotron component of the SED, while in 3C 454.3 the observed X-ray lies in the rising part of the inverse Compton component of the SED. Our SED modeling along with X-ray polarization observations favor a leptonic scenario for the observed X-ray emission in PKS 2155−304. The SED modeling for these specific IXPE epochs has not been presented before, allowing us to place additional constraints on the physical conditions in the jet. These results strengthen the case for a structured jet model where X-ray emission originates from a compact acceleration zone near the shock front, while lower-energy optical emission is produced in a broader, more turbulent region.
{"title":"Clues on the X-ray emission mechanism of blazars PKS 2155−304 and 3C 454.3 through polarization studies","authors":"Athira M. Bharathan , C.S. Stalin , Sunder Sahayanathan , Blesson Mathew","doi":"10.1016/j.jheap.2025.100472","DOIUrl":"10.1016/j.jheap.2025.100472","url":null,"abstract":"<div><div>X-ray polarization measurable with the imaging X-ray Polarimetry Explorer (<em>IXPE</em>) could constrain the long debated leptonic versus hadronic origin for the high energy component in the broad band spectral energy distribution (SED) of blazars. We report here the results from <em>IXPE</em> and SED modeling of PKS 2155−304 and 3C 454.3, a high and low synchrotron peaked blazar. For PKS 2155−304, from model-independent analysis, we found polarization angle <span><math><msub><mrow><mi>Ψ</mi></mrow><mrow><mi>X</mi></mrow></msub></math></span> = (130 ± 2.5) deg and polarization degree <span><math><msub><mrow><mi>Π</mi></mrow><mrow><mi>X</mi></mrow></msub></math></span> = (20.9 ± 1.8)% in the 2−8 keV band in agreement with spectro-polarimetric analysis. We found <span><math><msub><mrow><mi>Π</mi></mrow><mrow><mi>X</mi></mrow></msub></math></span> to vary with time and indications of it to vary between energies, suggesting that the emission regions are stratified. For 3C 454.3, we did not detect X-ray polarization in the June 2023 observation, analyzed here for the first time. The detection of X-ray polarization in PKS 2155−304 and its non-detection in 3C 454.3 is in accordance with the X-ray emission from synchrotron and inverse Compton process, respectively, operating in these sources. Further, our division of the dataset into finer time bins allows a more granular view of polarization variability. Additionally, we modeled the broadband SEDs of both the sources using data acquired quasi-simultaneously with <em>IXPE</em>, in the optical, UV and X-rays from <em>Swift</em>, <em>AstroSat</em> and <em>γ</em>-rays from <em>Fermi</em>. In PKS 2155−304, the observed X-ray is found to lie in the high energy tail of the synchrotron component of the SED, while in 3C 454.3 the observed X-ray lies in the rising part of the inverse Compton component of the SED. Our SED modeling along with X-ray polarization observations favor a leptonic scenario for the observed X-ray emission in PKS 2155−304. The SED modeling for these specific <em>IXPE</em> epochs has not been presented before, allowing us to place additional constraints on the physical conditions in the jet. These results strengthen the case for a structured jet model where X-ray emission originates from a compact acceleration zone near the shock front, while lower-energy optical emission is produced in a broader, more turbulent region.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100472"},"PeriodicalIF":10.5,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222607","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 : 2025-09-24DOI: 10.1016/j.jheap.2025.100483
Rahul Bhagat, B. Mishra
We have performed the dynamical system analysis to obtain the critical point in which, the value of the geometric and dynamical parameters satisfy the late-time cosmic behavior of the Universe. At the outset, the modified Friedmann equations have been reformulated into a system of coupled differential equations to ensure that the minimal set of equations required for a second-order gravity. Then these equations are solved numerically to constrain the parameters with Markov Chain Monte Carlo (MCMC) techniques. Cosmic Chronometers (CC) and high-precision Pantheon+ Type Ia Supernovae datasets are used to constrain the parameters. The evolution of key cosmological parameters indicates that the model exhibits quintessence-like behavior at present, with a tendency to converge towards the ΛCDM model at late-times. The dynamic system analysis provided the critical points that correspond to different phases of the Universe, which are analyzed in detail. The existence of a stable de Sitter attractor confirms the accelerating behavior of the model.
{"title":"Accelerating behavior from dynamical system analysis parameters","authors":"Rahul Bhagat, B. Mishra","doi":"10.1016/j.jheap.2025.100483","DOIUrl":"10.1016/j.jheap.2025.100483","url":null,"abstract":"<div><div>We have performed the dynamical system analysis to obtain the critical point in which, the value of the geometric and dynamical parameters satisfy the late-time cosmic behavior of the Universe. At the outset, the modified Friedmann equations have been reformulated into a system of coupled differential equations to ensure that the minimal set of equations required for a second-order <span><math><mi>f</mi><mo>(</mo><mi>Q</mi><mo>)</mo></math></span> gravity. Then these equations are solved numerically to constrain the parameters with Markov Chain Monte Carlo (MCMC) techniques. Cosmic Chronometers (CC) and high-precision Pantheon<sup>+</sup> Type Ia Supernovae datasets are used to constrain the parameters. The evolution of key cosmological parameters indicates that the model exhibits quintessence-like behavior at present, with a tendency to converge towards the ΛCDM model at late-times. The dynamic system analysis provided the critical points that correspond to different phases of the Universe, which are analyzed in detail. The existence of a stable de Sitter attractor confirms the accelerating behavior of the model.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100483"},"PeriodicalIF":10.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159778","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 Nuclear Stellar Disk (NSD), together with the Nuclear Stellar Cluster and the supermassive black hole Sgr A*, forms the central region of the Milky Way. Galactic X-ray background emission is known to be associated with the old stellar population, predominantly produced by accreting white dwarfs. In this work we characterize the X-ray emission of the Galactic Center (GC) region using wide-field observations with the ART-XC telescope on-board the SRG observatory in the 4−12 keV energy band. Our analysis demonstrates that the X-ray emission of the GC at a spatial scale of a few hundred parsecs is dominated by the regularly-shaped NSD aligned in the Galactic plane, and characterized by latitudinal and longitudinal scale heights of ∼20 pc and ∼100 pc, respectively. The measured flux erg s−1 cm−2 in the 4−12 keV band corresponds to a luminosity of erg s−1, assuming the GC distance of 8.178 kpc. The average mass-normalized X-ray emissivity of the NSD, erg s−1 M, exceeds the corresponding value for the Galactic ridge by a factor of , confirming other studies. We also perform a deprojection of the observed NSD surface brightness distribution in order to construct a three-dimensional X-ray luminosity density model, which can be directly compared to the existing 3D stellar mass models. Finally, we conclude that the spatial distribution of the X-ray emission from the NSD is consistent with the most recent stellar mass density distribution model within 30%, which suggests that this emission is dominated by unresolved point X-ray sources rather than by diffuse X-ray emission.
{"title":"X-ray emission of the Nuclear Stellar Disk as seen by SRG/ART-XC","authors":"Valentin Nezabudkin , Roman Krivonos , Sergey Sazonov , Rodion Burenin , Alexander Lutovinov , Ekaterina Filippova , Alexey Tkachenko , Mikhail Pavlinsky","doi":"10.1016/j.jheap.2025.100473","DOIUrl":"10.1016/j.jheap.2025.100473","url":null,"abstract":"<div><div>The Nuclear Stellar Disk (NSD), together with the Nuclear Stellar Cluster and the supermassive black hole Sgr A*, forms the central region of the Milky Way. Galactic X-ray background emission is known to be associated with the old stellar population, predominantly produced by accreting white dwarfs. In this work we characterize the X-ray emission of the Galactic Center (GC) region using wide-field observations with the ART-XC telescope on-board the <em>SRG</em> observatory in the 4−12 keV energy band. Our analysis demonstrates that the X-ray emission of the GC at a spatial scale of a few hundred parsecs is dominated by the regularly-shaped NSD aligned in the Galactic plane, and characterized by latitudinal and longitudinal scale heights of ∼20 pc and ∼100 pc, respectively. The measured flux <span><math><mo>(</mo><msubsup><mrow><mn>6.8</mn></mrow><mrow><mo>−</mo><mn>0.3</mn></mrow><mrow><mo>+</mo><mn>0.1</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup></math></span>erg s<sup>−1</sup> cm<sup>−2</sup> in the 4−12 keV band corresponds to a luminosity of <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>4</mn><mtext>–</mtext><mn>12</mn><mspace></mspace><mrow><mi>keV</mi></mrow></mrow></msub><mo>=</mo><mo>(</mo><msubsup><mrow><mn>5.9</mn></mrow><mrow><mo>−</mo><mn>0.3</mn></mrow><mrow><mo>+</mo><mn>0.1</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>36</mn></mrow></msup></math></span>erg s<sup>−1</sup>, assuming the GC distance of 8.178 kpc. The average mass-normalized X-ray emissivity of the NSD, <span><math><mo>〈</mo><mi>L</mi><mo>/</mo><mi>M</mi><mo>〉</mo><mo>=</mo><mo>(</mo><msubsup><mrow><mn>5.6</mn></mrow><mrow><mo>−</mo><mn>0.7</mn></mrow><mrow><mo>+</mo><mn>0.5</mn></mrow></msubsup><mo>)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>27</mn></mrow></msup></math></span>erg s<sup>−1</sup> M<span><math><msubsup><mrow></mrow><mrow><mo>⊙</mo></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span>, exceeds the corresponding value for the Galactic ridge by a factor of <span><math><msubsup><mrow><mn>3.3</mn></mrow><mrow><mo>−</mo><mn>0.5</mn></mrow><mrow><mo>+</mo><mn>0.4</mn></mrow></msubsup></math></span>, confirming other studies. We also perform a deprojection of the observed NSD surface brightness distribution in order to construct a three-dimensional X-ray luminosity density model, which can be directly compared to the existing 3D stellar mass models. Finally, we conclude that the spatial distribution of the X-ray emission from the NSD is consistent with the most recent stellar mass density distribution model within 30%, which suggests that this emission is dominated by unresolved point X-ray sources rather than by diffuse X-ray emission.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100473"},"PeriodicalIF":10.5,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159861","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 : 2025-09-22DOI: 10.1016/j.jheap.2025.100471
S.D. Odintsov , V.K. Oikonomou , G.S. Sharov
A class of viable gravity models which can provide a unified description of inflation with the dark energy era is confronted with the latest observational data on the dark energy era. These models have the unique characteristic that the de Sitter scalaron mass in the Einstein frame counterpart theory is a monotonic function of the curvature, which renders them viable descriptions for both the inflationary and the late-time acceleration eras. We also compare these models with other well-known viable gravity models and with the Λ-Cold-Dark-Matter model. As we show, the most phenomenologically successful models are those which deviate significantly from the Λ-Cold-Dark-Matter model. Also some of the models presented, provide a statistically favorable description of the dark energy eras, compared with the exponential gravity model and of course compared with the Λ-Cold-Dark-Matter model. All the models we present in this article are confronted with the observational data from the Planck collaboration, the Pantheon plus data from Type Ia supernovae, the two rounds of observations of the Dark Energy Spectroscopic Instrument, data from baryon acoustic oscillations and the Hubble constant measurements. As we show, two of the models are statistically favorable by the data.
{"title":"Dynamical dark energy from F(R) gravity models unifying inflation with dark energy: Confronting the latest observational data","authors":"S.D. Odintsov , V.K. Oikonomou , G.S. Sharov","doi":"10.1016/j.jheap.2025.100471","DOIUrl":"10.1016/j.jheap.2025.100471","url":null,"abstract":"<div><div>A class of viable <span><math><mi>F</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> gravity models which can provide a unified description of inflation with the dark energy era is confronted with the latest observational data on the dark energy era. These models have the unique characteristic that the de Sitter scalaron mass in the Einstein frame counterpart theory is a monotonic function of the curvature, which renders them viable descriptions for both the inflationary and the late-time acceleration eras. We also compare these models with other well-known viable <span><math><mi>F</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> gravity models and with the Λ-Cold-Dark-Matter model. As we show, the most phenomenologically successful models are those which deviate significantly from the Λ-Cold-Dark-Matter model. Also some of the models presented, provide a statistically favorable description of the dark energy eras, compared with the exponential <span><math><mi>F</mi><mo>(</mo><mi>R</mi><mo>)</mo></math></span> gravity model and of course compared with the Λ-Cold-Dark-Matter model. All the models we present in this article are confronted with the observational data from the Planck collaboration, the Pantheon plus data from Type Ia supernovae, the two rounds of observations of the Dark Energy Spectroscopic Instrument, data from baryon acoustic oscillations and the Hubble constant measurements. As we show, two of the models are statistically favorable by the data.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100471"},"PeriodicalIF":10.5,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159859","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}
Electron-capture supernovae (ECSNe) have emerged as a compelling formation channel for low-mass neutron stars, bolstered by decades of theoretical work and increasingly supported by observational evidence, including the recent identification of SN 2018zd. Motivated by this, we investigate the influence of fermionic asymmetric dark matter (ADM) on the equilibrium structure of progenitor cores and the formation of their neutron star remnants. Using a general relativistic two-fluid formalism, we model the coupled evolution of ordinary matter (OM) and ADM, treated as separately conserved fluids interacting solely through gravity. Our analysis focuses on neon-rich white dwarfs (Ne WDs), which are typical progenitor cores for ECSNe. We assume conservation of both baryon number () and DM particle number () during collapse, allowing for a consistent mapping between progenitor and remnant configurations. We find that ADM significantly enhances the central density of the WD progenitor. This lowers the threshold gravitational mass required to initiate electron capture, enabling ECSNe from lower-mass progenitors. The resulting remnants are stable, DM-admixed neutron stars with gravitational masses potentially well below current observational bounds. Moreover, we find that the conversion energy during the WD-to-NS conversion is also significantly reduced for higher ADM particle masses and fractions, suggesting that unusually low-energy ECSNe may serve as potential indicators of ADM involvement in stellar collapse.
{"title":"Triggering electron capture supernovae: Dark matter effects in degenerate white-dwarf-like cores of super-asymptotic giant branch stars","authors":"Vishal Parmar , Domenico Scordino , Ignazio Bombaci","doi":"10.1016/j.jheap.2025.100470","DOIUrl":"10.1016/j.jheap.2025.100470","url":null,"abstract":"<div><div>Electron-capture supernovae (ECSNe) have emerged as a compelling formation channel for low-mass neutron stars, bolstered by decades of theoretical work and increasingly supported by observational evidence, including the recent identification of SN 2018zd. Motivated by this, we investigate the influence of fermionic asymmetric dark matter (ADM) on the equilibrium structure of progenitor cores and the formation of their neutron star remnants. Using a general relativistic two-fluid formalism, we model the coupled evolution of ordinary matter (OM) and ADM, treated as separately conserved fluids interacting solely through gravity. Our analysis focuses on neon-rich white dwarfs (Ne WDs), which are typical progenitor cores for ECSNe. We assume conservation of both baryon number (<span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>B</mi></mrow></msub></math></span>) and DM particle number (<span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>D</mi></mrow></msub></math></span>) during collapse, allowing for a consistent mapping between progenitor and remnant configurations. We find that ADM significantly enhances the central density of the WD progenitor. This lowers the threshold gravitational mass <span><math><msup><mrow><mi>M</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> required to initiate electron capture, enabling ECSNe from lower-mass progenitors. The resulting remnants are stable, DM-admixed neutron stars with gravitational masses potentially well below current observational bounds. Moreover, we find that the conversion energy during the WD-to-NS conversion is also significantly reduced for higher ADM particle masses and fractions, suggesting that unusually low-energy ECSNe may serve as potential indicators of ADM involvement in stellar collapse.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100470"},"PeriodicalIF":10.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145110181","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 : 2025-09-17DOI: 10.1016/j.jheap.2025.100469
Shubhrangshu Ghosh , Sudip Bhattacharyya
We investigate the global energetics of the magnetized accretion-induced outflow in the context of a two-temperature accreting plasma around black holes (BHs), explicitly incorporating the effect of the ‘Ohmic heating’. We obtain substantially high electron temperature, with even reaching in the inner regions of the flow. The radiative cooling is primarily determined by the synchrotron loss which mostly dominates the inner accretion region, more so, in the context of flows towards super massive BHs (SMBHs). However, at a relatively high , bremsstrahlung emission dominates most of the accretion region. For stellar mass BHs, on the other hand, synchrotron dominates the cooling for a considerable portion of the inner and middle accretion region, with emission cooling rates significantly higher. Electron heating is primarily governed by turbulent Ohmic dissipation, with primarily determined by the balance between Ohmic heating and synchrotron cooling. We obtain relatively high values of luminosity reaching and surpassing , from the inner accretion region, corresponding to , respectively, for moderately advective flows. Based on the estimates of the ratio of ‘mass flow rate into the jet’ to ‘mass inflow rate’ , and comparing our theoretical finding with the ratio of radio-to-X-ray luminosities for several BH X-ray binaries (BHXRBs), we tentatively suggest that both steady and transient jets in BHXRBs could primarily be accretion powered, indicating a
{"title":"Energetics of magnetized accretion-induced outflows around black holes: Description of a unified disk-jet connection","authors":"Shubhrangshu Ghosh , Sudip Bhattacharyya","doi":"10.1016/j.jheap.2025.100469","DOIUrl":"10.1016/j.jheap.2025.100469","url":null,"abstract":"<div><div>We investigate the global energetics of the magnetized accretion-induced outflow in the context of a two-temperature accreting plasma around black holes (BHs), explicitly incorporating the effect of the ‘Ohmic heating’. We obtain substantially high electron temperature, with <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> even reaching <span><math><mo>∼</mo><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>10</mn></mrow></msup><mi>K</mi></math></span> in the inner regions of the flow. The radiative cooling is primarily determined by the synchrotron loss which mostly dominates the inner accretion region, more so, in the context of flows towards super massive BHs (SMBHs). However, at a relatively high <span><math><mover><mrow><mi>M</mi></mrow><mrow><mo>˙</mo></mrow></mover><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup><msub><mrow><mover><mrow><mi>M</mi></mrow><mrow><mo>˙</mo></mrow></mover></mrow><mrow><mi>Edd</mi></mrow></msub></math></span>, bremsstrahlung emission dominates most of the accretion region. For stellar mass BHs, on the other hand, synchrotron dominates the cooling for a considerable portion of the inner and middle accretion region, with emission cooling rates significantly higher. Electron heating is primarily governed by turbulent Ohmic dissipation, with <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span> primarily determined by the balance between Ohmic heating and synchrotron cooling. We obtain relatively high values of luminosity reaching <span><math><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>42</mn></mrow></msup><mspace></mspace><mrow><mi>erg</mi><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> and surpassing <span><math><msup><mrow><mn>10</mn></mrow><mrow><mn>35</mn></mrow></msup><mspace></mspace><mrow><mi>erg</mi><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>, from the inner accretion region, corresponding to <span><math><msub><mrow><mi>M</mi></mrow><mrow><mi>BH</mi></mrow></msub><mo>=</mo><mo>(</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup><mo>,</mo><mn>10</mn><mo>)</mo><mspace></mspace><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>, respectively, for moderately advective flows. Based on the estimates of the ratio of ‘mass flow rate into the jet’ to ‘mass inflow rate’ <span><math><mo>(</mo><msub><mrow><mover><mrow><mi>M</mi></mrow><mrow><mo>˙</mo></mrow></mover></mrow><mrow><mi>j</mi></mrow></msub><mo>/</mo><mover><mrow><mi>M</mi></mrow><mrow><mo>˙</mo></mrow></mover><mo>)</mo></math></span>, and comparing our theoretical finding with the ratio of radio-to-X-ray luminosities for several BH X-ray binaries (BHXRBs), we tentatively suggest that both steady and transient jets in BHXRBs could primarily be accretion powered, indicating a ","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100469"},"PeriodicalIF":10.5,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099039","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 : 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":"2025-09-16","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}
A comprehensive analysis of quasi-periodic oscillations (QPOs) in the multi-wavelength observations of blazars has been carried out. Utilizing 15 years of Fermi-LAT observations of seven blazars in our sample, we identify both long-term and transient QPOs in the gamma-ray light curves, with timescales ranging from a few months to years. These periodicities were detected using the Lomb-Scargle periodogram (LSP) and REDFIT techniques. To robustly evaluate the statistical significance of the quasi-periodic signals observed in the LSPs, 2 synthetic γ-ray light curves were generated for each source using a stochastic model known as the Damped Random Walk (DRW). These gamma-ray QPOs are further supported by the detection of optical QPOs exhibiting similar timescales. A cross-correlation analysis between γ-rays and optical emissions reveals a significant peak () at or close to zero-lag. To investigate the physical origin of the observed gamma-ray QPOs with different timescales, we explore several plausible scenarios, with particular emphasis on a relativistic jet hosted by one of the black holes in a supermassive binary black hole (SMBBH) system, accretion disc model, and helical motion of magnetized plasma blob within the jet. The transient gamma-ray QPOs of month-like timescales are interpreted within the framework of the helical motion of plasma blob in jet, while the long-duration QPOs with multi-year timescales are explained using the SMBBH scenario. The gamma-ray light curves were modeled by employing a Markov Chain Monte Carlo (MCMC) approach, allowing us to constrain key physical parameters such as the jet Lorentz factor (Γ) and the viewing angle between the observer's line of sight (ψ) relative to the spin axis of SMBH.
{"title":"Exploring year-timescale transient and long-term quasi-periodic oscillations in optical and gamma-ray light curves of blazars","authors":"Ajay Sharma , Sakshi Chaudhary , Aishwarya Sarath , Debanjan Bose","doi":"10.1016/j.jheap.2025.100466","DOIUrl":"10.1016/j.jheap.2025.100466","url":null,"abstract":"<div><div>A comprehensive analysis of quasi-periodic oscillations (QPOs) in the multi-wavelength observations of blazars has been carried out. Utilizing 15 years of Fermi-LAT observations of seven blazars in our sample, we identify both long-term and transient QPOs in the gamma-ray light curves, with timescales ranging from a few months to years. These periodicities were detected using the Lomb-Scargle periodogram (LSP) and REDFIT techniques. To robustly evaluate the statistical significance of the quasi-periodic signals observed in the LSPs, 2<span><math><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>5</mn></mrow></msup></math></span> synthetic <em>γ</em>-ray light curves were generated for each source using a stochastic model known as the Damped Random Walk (DRW). These gamma-ray QPOs are further supported by the detection of optical QPOs exhibiting similar timescales. A cross-correlation analysis between <em>γ</em>-rays and optical emissions reveals a significant peak (<span><math><mo>></mo><mn>3</mn><mi>σ</mi></math></span>) at or close to zero-lag. To investigate the physical origin of the observed gamma-ray QPOs with different timescales, we explore several plausible scenarios, with particular emphasis on a relativistic jet hosted by one of the black holes in a supermassive binary black hole (SMBBH) system, accretion disc model, and helical motion of magnetized plasma blob within the jet. The transient gamma-ray QPOs of month-like timescales are interpreted within the framework of the helical motion of plasma blob in jet, while the long-duration QPOs with multi-year timescales are explained using the SMBBH scenario. The gamma-ray light curves were modeled by employing a Markov Chain Monte Carlo (MCMC) approach, allowing us to constrain key physical parameters such as the jet Lorentz factor (Γ) and the viewing angle between the observer's line of sight (<em>ψ</em>) relative to the spin axis of SMBH.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100466"},"PeriodicalIF":10.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145098696","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 : 2025-09-16DOI: 10.1016/j.jheap.2025.100468
Pius Privatus , Umananda Dev Goswami
In this study, we use the luminous volume-limited samples obtained from the twelfth release of Sloan Digital Sky Survey data and mergers from Galaxy Zoo Project to investigate the influence of group richness in shaping galaxy properties' distributions and their relationships in the local Universe by comparison of mergers and non-mergers. The galaxies were restricted into mass-limited subsamples of low-mass, intermediate-mass and high-mass, assigned into groups from poor to rich group systems, where the distributions of star formation rate (SFR), specific SFR (SSFR), spectral index (4000) and colour properties between mergers and non-mergers for all subsamples and their relations with stellar mass of galaxies are compared. The study revealed a significant difference in the distributions between mergers' and non-mergers' properties for low-mass galaxies, while for high-mass galaxies the difference is very weak. For the low-mass sample, mergers possess higher SFR, SSFR than non-mergers when the group richness is kept constant, while for high-mass poor group galaxies have higher SFR, SSFR than rich group galaxies when merging status is kept constant. Mergers resemble young stellar populations and are bluer than non-mergers for low-mass, while for high-mass, mergers and non-mergers have comparable SFR, SSFR, (4000), and colour. The study concludes that group richness and stellar mass influence the mergers' and non-mergers' properties' distributions, and their relationships.
{"title":"Galaxy evolution in the local Universe: Group richness effects on mergers and non-mergers","authors":"Pius Privatus , Umananda Dev Goswami","doi":"10.1016/j.jheap.2025.100468","DOIUrl":"10.1016/j.jheap.2025.100468","url":null,"abstract":"<div><div>In this study, we use the luminous volume-limited samples obtained from the twelfth release of Sloan Digital Sky Survey data and mergers from Galaxy Zoo Project to investigate the influence of group richness in shaping galaxy properties' distributions and their relationships in the local Universe by comparison of mergers and non-mergers. The galaxies were restricted into mass-limited subsamples of low-mass, intermediate-mass and high-mass, assigned into groups from poor to rich group systems, where the distributions of star formation rate (SFR), specific SFR (SSFR), spectral index <span><math><msub><mrow><mtext>D</mtext></mrow><mrow><mi>n</mi></mrow></msub></math></span> (4000) and <span><math><mi>u</mi><mo>−</mo><mi>r</mi></math></span> colour properties between mergers and non-mergers for all subsamples and their relations with stellar mass of galaxies are compared. The study revealed a significant difference in the distributions between mergers' and non-mergers' properties for low-mass galaxies, while for high-mass galaxies the difference is very weak. For the low-mass sample, mergers possess higher SFR, SSFR than non-mergers when the group richness is kept constant, while for high-mass poor group galaxies have higher SFR, SSFR than rich group galaxies when merging status is kept constant. Mergers resemble young stellar populations and are bluer than non-mergers for low-mass, while for high-mass, mergers and non-mergers have comparable SFR, SSFR, <span><math><msub><mrow><mtext>D</mtext></mrow><mrow><mi>n</mi></mrow></msub></math></span> (4000), and <span><math><mi>u</mi><mo>−</mo><mi>r</mi></math></span> colour. The study concludes that group richness and stellar mass influence the mergers' and non-mergers' properties' distributions, and their relationships.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100468"},"PeriodicalIF":10.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145098695","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 : 2025-09-16DOI: 10.1016/j.jheap.2025.100467
Paulo E. Stecchini , Francisco Jablonski , Marcos P. Diaz , Alexandre S. Oliveira , Flavio D'Amico , Natália Palivanas
We analyse the spectral energy distribution (SED) of the eclipsing supersoft X-ray source CAL 87 covering wavelengths from X-rays to the near-infrared. Our study incorporates 26 data points across ultraviolet to near-infrared, sourced from published literature, unpublished data, and new observations. In addition, archival XMM-Newton spectra were used to represent the X-ray emission. Care was taken to use out-of-eclipse flux measurements when the irradiated side of the companion faces the observer. The SED model includes contributions from a central source, a reprocessed accretion disk, and an irradiated companion star atmosphere, resulting in a good match to the observed fluxes. The revised and new parameters for the disk and the central source align with previous studies and match expectations for such systems. The temperature of the irradiated side of the companion star was estimated based on its colour during the secondary eclipse. This work highlights the importance of broad wavelength coverage for understanding the properties of supersoft X-ray sources.
{"title":"Spectral energy distribution analysis of the supersoft X-ray source CAL 87: Multiwavelength constraints","authors":"Paulo E. Stecchini , Francisco Jablonski , Marcos P. Diaz , Alexandre S. Oliveira , Flavio D'Amico , Natália Palivanas","doi":"10.1016/j.jheap.2025.100467","DOIUrl":"10.1016/j.jheap.2025.100467","url":null,"abstract":"<div><div>We analyse the spectral energy distribution (SED) of the eclipsing supersoft X-ray source CAL<!--> <!-->87 covering wavelengths from X-rays to the near-infrared. Our study incorporates 26 data points across ultraviolet to near-infrared, sourced from published literature, unpublished data, and new observations. In addition, archival <em>XMM-Newton</em> spectra were used to represent the X-ray emission. Care was taken to use out-of-eclipse flux measurements when the irradiated side of the companion faces the observer. The SED model includes contributions from a central source, a reprocessed accretion disk, and an irradiated companion star atmosphere, resulting in a good match to the observed fluxes. The revised and new parameters for the disk and the central source align with previous studies and match expectations for such systems. The temperature of the irradiated side of the companion star was estimated based on its <span><math><mi>B</mi><mo>−</mo><mi>V</mi></math></span> colour during the secondary eclipse. This work highlights the importance of broad wavelength coverage for understanding the properties of supersoft X-ray sources.</div></div>","PeriodicalId":54265,"journal":{"name":"Journal of High Energy Astrophysics","volume":"50 ","pages":"Article 100467"},"PeriodicalIF":10.5,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099037","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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