Astroparticle Physics最新文献

{"title":"Utilizing simulated event lists in IACT gamma-ray astronomy","authors":"M. Holler ,&nbsp;M. de Naurois ,&nbsp;S. Panny ,&nbsp;R. Rauth","doi":"10.1016/j.astropartphys.2025.103186","DOIUrl":"10.1016/j.astropartphys.2025.103186","url":null,"abstract":"<div><div>We present a new approach for calculating the IACT detector response of high-level analyses with publicly available software based on dedicated simulations of the individual observations. For each of them, a corresponding event list is exported, paralleling the event list of the actual data. The information contained in these simulated lists can be utilized flexibly, without the need for but also being able to reduce it to the standard IRF scheme. We show that standard IRFs from simulated event lists yield consistent results, illustrating the validity of the concept. To improve on the standard response generation, we then demonstrate how to calculate the final IRFs for a given analysis geometry directly from the simulated event lists. The result is a more accurate description, where the change in IRF methodology leads to considerable differences. Finally, we introduce a new method of generating background models based on simulated event lists. By properly considering observation and detector conditions, the new approach provides an accurate description of the <span><math><mi>γ</mi></math></span>-like background, exhibiting good stability and a moderate systematics level.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103186"},"PeriodicalIF":2.9,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Identification of gamma ray pulsar candidates in the Fermi-LAT 4FGL-DR4 unassociated sources using supervised machine learning","authors":"A. Pathania ,&nbsp;K.K. Singh ,&nbsp;S.K. Singh ,&nbsp;A. Tolamatti ,&nbsp;B.B. Singh ,&nbsp;K.K. Yadav","doi":"10.1016/j.astropartphys.2025.103185","DOIUrl":"10.1016/j.astropartphys.2025.103185","url":null,"abstract":"<div><div>The Large Area Telescope (LAT) on board the <em>Fermi</em> Gamma-ray Space Telescope has been continuously providing good quality survey data of the entire sky in the high energy range from 30 MeV to 500 GeV and above since August 2008. A succession of gamma-ray source catalogs is published after a comprehensive analysis of the <em>Fermi</em>–LAT data. The most recent release of data in the fourth <em>Fermi</em>–LAT catalog of gamma-ray sources (4FGL-DR4), based on the first 14 years of observations in the energy band 50 MeV- 1 TeV, contains 7195 sources. A large fraction (<span><math><mo>∼</mo></math></span> 33%) of this population has no known counterparts in the lower wave bands. Such high energy gamma-ray sources are referred to as unassociated or unidentified. An appropriate classification of these objects into known type of gamma-ray sources such as the active galactic nuclei or pulsars is essential for population studies and pointed multi-wavelength observations to probe the radiative processes. In this work, we perform a detailed classification of the unassociated sources reported in the 4FGL-DR4 catalog using two supervised machine learning techniques- Random Forest and Extreme Gradient Boosting. We mainly focus on the identification of new gamma-ray pulsar candidates by making use of different observational features derived from the long-term observations with the <em>Fermi</em>–LAT and reported in the incremental 4FGL-DR4 catalog. We also explore the effects of data balancing approach on the classification of the <em>Fermi</em>–LAT unassociated sources.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103185"},"PeriodicalIF":2.9,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Likelihood-based reconstruction of muon lateral distribution function using combined integrator and binary detector modes","authors":"A.D. Supanitsky,&nbsp;D. Ravignani,&nbsp;V.V. Kizakke Covilakam","doi":"10.1016/j.astropartphys.2025.103184","DOIUrl":"10.1016/j.astropartphys.2025.103184","url":null,"abstract":"<div><div>The origin of ultra-high-energy cosmic rays, with energies <span><math><mrow><mi>E</mi><mo>≥</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>18</mn></mrow></msup><mspace></mspace><mi>eV</mi></mrow></math></span>, remains unknown. Among the key observables used to investigate their nature are the energy spectrum, the arrival direction distribution, and the composition as a function of energy. The composition of the primary cosmic ray is inferred from properties of the extensive air showers they initiate, particularly from parameters sensitive to the primary mass. The most sensitive parameters to the primary mass are the atmospheric depth of the shower maximum, typically measured with fluorescence telescopes, and the muon content of the shower, measured using dedicated muon detectors. A commonly used observable in composition studies is the muon density at a fixed distance from the shower axis, derived by evaluating the reconstructed muon lateral distribution function (MLDF) at a reference distance. A specific type of muon detector features two acquisition modes: binary and integrator (commonly referred to as ADC mode, for Analog-to-Digital Converter). The binary mode allows for direct muon counting, while the ADC mode infers the muon number from the integrated signal of the detector response. Existing methods reconstruct the MLDF using data from either acquisition mode individually, or by combining both, but usually assigning a single mode per detector station in a given event. This work presents a novel method to reconstruct the MLDF based on a likelihood approach that simultaneously incorporates data from both acquisition modes at each detector station. We apply our method to the underground muon detectors of the Pierre Auger Observatory as a case study. However, this general approach can be applied to future detectors with dual acquisition capabilities. Our results demonstrate that the combined method outperforms traditional techniques that rely solely on either binary or ADC mode data.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103184"},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"SMIET: Fast and accurate synthesis of radio pulses from extensive air shower using simulated templates","authors":"Mitja Desmet ,&nbsp;Stijn Buitink ,&nbsp;Tim Huege ,&nbsp;Keito Watanabe","doi":"10.1016/j.astropartphys.2025.103182","DOIUrl":"10.1016/j.astropartphys.2025.103182","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Interpreting the data from radio detectors for extensive air showers typically relies on Monte-Carlo based simulation codes, which, despite their accuracy are computationally expensive and present bottlenecks for analyses. To address this issue we have developed a novel forward model called template synthesis, which synthesises the radio emission from cosmic ray air showers in a matter of seconds. This hybrid approach uses a microscopically simulated, sliced shower (the origin) as an input. It rescales the emission from each slice individually to synthesise the emission from a shower with different properties (the target). In this process it employs semi-analytical relations dependent on the shower age within the slice. We describe the connection between an antenna and a slice using the viewing angle and normalise the emission from every slice with respect to the air shower geometry using a set of scaling relations. In order to be able to change the arrival direction during synthesis, we adjust the phases based on the expected geometrical delays.&lt;/div&gt;&lt;div&gt;We benchmark the method by comparing synthesised traces to CoREAS simulations over a wide frequency range of [30, 500] &lt;span&gt;&lt;math&gt;&lt;mtext&gt;MHz&lt;/mtext&gt;&lt;/math&gt;&lt;/span&gt;. We compare the signal amplitudes as well as the fluences. The synthesis quality is primarily influenced by the difference in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;max&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; between the origin and target shower, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;max&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. When &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;max&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mtext&gt;g&lt;/mtext&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mtext&gt;cm&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; , the scatter on the maximum amplitudes of the geomagnetic traces is at most 4%. For the traces from the charge-excess component this scatter is smaller than 6%. We also observe a bias with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;max&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; up to 5% for both components, which appears to depend on the antenna position. Since the bias is symmetrical around &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Δ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;max&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mtext&gt;g&lt;/mtext&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mtext&gt;cm&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, we can use an interpolation approach to correct for it. While it improves the accuracy of the synthesis, it requires multiple origin showers, increasing the complexity of the approach.&lt;/div&gt;&lt;div&gt;We have implemented the template synthesis algorithm in an open-source Python package called &lt;span&gt;SMIET&lt;/span&gt;, which includes all the necessary parameters to apply the method. Users only need to provide adequate origin showers. The package provides an imple","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103182"},"PeriodicalIF":2.9,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"A new method for detecting heavy cosmic ray component above the knee region","authors":"Jing Zhao,&nbsp;Jia Liu","doi":"10.1016/j.astropartphys.2025.103180","DOIUrl":"10.1016/j.astropartphys.2025.103180","url":null,"abstract":"<div><div>The precise energy spectrum of cosmic rays with different compositions is crucial for studying the origin of cosmic rays (CRs). Spectral features of single-component spectra provide an opportunity to investigate the acceleration and propagation of the “knee”. Ground-based experimental measurements of secondary particles are influenced by energy components and hadronic interactions, leading to significant uncertainties in component-specific energy spectra. The intensity of the direct Cherenkov (DC) light emitted by the primary cosmic ray particles is proportional to the square of their charge (<span><math><msup><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span>), which serves as a valuable parameter for component discrimination. The fluorescence yield is proportional to the energy of primary cosmic ray, which can be used to reconstruct the primary particle’s energy. This project proposes a new method for measuring heavy components at the knee region: hybrid measurements combining direct Cherenkov and fluorescence detection at the high altitudes of the stratosphere. In this paper, the characterization of direct Cherenkov and fluorescence at high altitudes has been investigated, and a conceptual detector has been proposed based on the results of the study. Finally, preliminary simulation results indicate that the aperture is 85.98 <span><math><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mi>sr</mi></mrow></math></span> and retention ratio for Fe is approximately <span><math><mrow><mn>0</mn><mo>.</mo><mn>8153</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>0017</mn></mrow></math></span>.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103180"},"PeriodicalIF":2.9,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Polarimetric evaluation of CdTe-Timepix3 detector module for THOR-SR Compton telescope","authors":"J.F. Sousa ,&nbsp;M. Letra ,&nbsp;J.M. Maia ,&nbsp;R.M. Curado da Silva ,&nbsp;A.M.F. Trindade ,&nbsp;P. Carmo ,&nbsp;A.G. Neves ,&nbsp;J. Flunger ,&nbsp;G. Falcão ,&nbsp;J.R. Campos","doi":"10.1016/j.astropartphys.2025.103181","DOIUrl":"10.1016/j.astropartphys.2025.103181","url":null,"abstract":"<div><div>Gamma-ray polarimetry for the sub-MeV to lower-MeV band, an unexplored regime, requires the development of polarimeters that utilize novel space instrumentation with enhanced timing, imaging, and polarimetric capabilities, in addition to a robust spectroscopic response. THOR-SR is an astrophysics technology demonstrator to fly aboard the ESA vehicle Space Rider on a two-month mission. The main instrument is an all-sky Compton telescope composed of four layers, each layer with four modules based on 2.0 mm thick CdTe-Timepix3 detectors.</div><div>Herein, we evaluate the polarimetric performance of a 2.0 mm thick CdTe-Timepix3 detector with 256 × 256 pixels (55 μm pixel size, 1.98 cm² sensitive area, and featuring the Timepix3 chip). For gamma-ray beams, 100 % linearly polarized with energies within 100−300 keV, we explored a method for reconstructing Compton events based on Compton scattering kinematics. Using a selection process, we examined several empirical factors that influence the statistics in the azimuthal angular distribution of scattered gamma rays. Then, we present the response to unpolarized and polarized gamma rays, including beams with very close polarization angles. Finally, an estimate of the THOR-SR telescope's polarization sensitivity in Crab observations is presented.</div><div>The features of the CdTe-Timepix3 detector enable its operation as a fine Compton polarimeter, ensuring high modulation factors of ≈0.6 and a significantly greater Compton detection efficiency compared to other 2.0 mm thick pixelated CdTe/CZT polarimeters. The laboratory polarimeter exhibits a sub-degree angular sensitivity, capable of distinguishing polarization angles separated by &lt;1.0°, and reveals a residual statistical polarization fraction of ≈0.03. Minimum detectable polarization &lt;0.3 is foreseen in 20-day Crab observations with the THOR-SR Compton telescope.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103181"},"PeriodicalIF":2.9,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Revisiting the longitudinal development of electromagnetic air showers: Analytical improvements to the Greisen formalism with zenith angle dependence","authors":"Sebastián Mendizabal ,&nbsp;Nicolás Viaux M. ,&nbsp;Sebastián Tapia ,&nbsp;Raquel Pezoa R. ,&nbsp;Barbara Gutiérrez ,&nbsp;Constanza Valdivieso","doi":"10.1016/j.astropartphys.2025.103172","DOIUrl":"10.1016/j.astropartphys.2025.103172","url":null,"abstract":"<div><div>We present a new analytical approach to the longitudinal development of electromagnetic air showers, offering improvements to the classical Greisen formalism. We introduce a modified profile for the slope function <span><math><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mn>1</mn></mrow></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></math></span> that achieves an agreement less than 0.75% with the original <span><math><msub><mrow><mi>λ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> for shower age parameter <span><math><mi>s</mi></math></span> between <span><math><mrow><mn>0</mn><mo>.</mo><mn>3</mn><mo>&lt;</mo><mi>s</mi><mo>&lt;</mo><mn>1</mn><mo>.</mo><mn>4</mn></mrow></math></span>, where <span><math><mi>s</mi></math></span> represents the stage of shower development. Our new formalism provides an improved representation of shower evolution, particularly near and beyond the shower maximum. In addition, we propose a modified Greisen profile. Our implementation includes the zenith angle dependence on the number of particles at the detector level at high altitudes, making it particularly useful for high-altitude observatories. This expression is suitable for implementing air shower simulation tool fitting procedures over a wide range of energies and geometries. Our analysis shows that the modified Greisen profile provides better agreement with the expected evolution of particle numbers compared to the Greisen formulation when we compare it with CORSIKA simulations.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103172"},"PeriodicalIF":2.9,"publicationDate":"2025-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Effects of Bethe–Heitler pair production in ultraluminous X-ray sources","authors":"Gustavo E. Romero,&nbsp;Lucas M. Pasquevich,&nbsp;Leandro Abaroa","doi":"10.1016/j.astropartphys.2025.103173","DOIUrl":"10.1016/j.astropartphys.2025.103173","url":null,"abstract":"<div><div>Some black holes in X-ray binaries accrete at rates far above the Eddington limit. In this supercritical regime, photons are trapped in a radiation-dominated, geometrically thick disk. The innermost regions form a complex environment of intense radiation, strong magnetic fields, and powerful outflows, where radiation-driven winds expel large amounts of mass. These conditions suppress primary relativistic electrons within the transparent funnel along the black hole’s spin axis. We show that high-energy electrons can instead arise as secondary pairs from Bethe–Heitler interactions between relativistic protons and ambient photons. Using self-similar models of accretion disks with strong winds of ultraluminous X-ray sources (ULXs), we compute particle acceleration via magnetic reconnection and diffusive shocks, evaluate energy losses, and assess the efficiency and spectral imprint of Bethe–Heitler pair production. Our results suggest that secondary pairs can yield nonthermal radiation in the 0.1-100 MeV range with luminosities from <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>34</mn></mrow></msup></mrow></math></span> up to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>38</mn></mrow></msup></mrow></math></span> erg s⁻¹. This emission could be detectable by future MeV instruments from Galactic ULXs, offering <strong>evidence of relativistic protons</strong> in their inner funnels and revealing misaligned, otherwise hidden, super-Eddington sources in the Milky Way.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103173"},"PeriodicalIF":2.9,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145050580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Measurement of the re-entrant all-electron spectrum by the High-Energy Particle Detector on board the China Seismo-Electromagnetic Satellite","authors":"S. Amoroso ,&nbsp;M. Babu ,&nbsp;S. Bartocci ,&nbsp;R. Battiston ,&nbsp;S. Beolè ,&nbsp;W.J. Burger ,&nbsp;D. Campana ,&nbsp;P. Cipollone ,&nbsp;L. Conti ,&nbsp;A. Contin ,&nbsp;M. Cristoforetti ,&nbsp;C. De Donato ,&nbsp;C. De Santis ,&nbsp;A. Di Luca ,&nbsp;F.M. Follega ,&nbsp;G. Gebbia ,&nbsp;R. Iuppa ,&nbsp;A. Lega ,&nbsp;M. Lolli ,&nbsp;M. Martucci ,&nbsp;P. Zuccon","doi":"10.1016/j.astropartphys.2025.103170","DOIUrl":"10.1016/j.astropartphys.2025.103170","url":null,"abstract":"<div><div>Interactions of primary cosmic rays with residual atmospheric nuclei produce secondary leptons through the decay chain of short-lived pions. Even though generated with an upward direction, a fraction of these secondary electrons and positrons is bent back downward towards the Earth by the geomagnetic field lines (hence they are called re-entrant albedo). In this paper, we report on a new measurement of the re-entrant all-electron differential flux in the energy range 10-100 MeV, performed by the High-Energy Particle Detector (HEPD-01) on board the China Seismo-Electromagnetic Satellite (CSES-01) in the near-equatorial region at about 500 km altitude between 2018 and 2022. This analysis focuses on the re-entrant all-electron spectrum that covers the low energy interval in a geographical region characterized by a substantial lack of recent experimental data and can contribute to a more accurate definition of secondary electron and positron population distribution and refine the radiation models in the Earth’s magnetosphere.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103170"},"PeriodicalIF":2.9,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145027840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

{"title":"Crystal Eye: All sky MeV monitor with high precision real-time localization","authors":"R. Aloisio ,&nbsp;U. Atalay ,&nbsp;B. Banerjee ,&nbsp;F.C.T. Barbato ,&nbsp;E. Bissaldi ,&nbsp;M. Branchesi ,&nbsp;F. Capitanio ,&nbsp;E. Casilli ,&nbsp;R. Colalillo ,&nbsp;I. De Mitri ,&nbsp;A. De Santis ,&nbsp;A. Di Giovanni ,&nbsp;M. Fernandez Alonso ,&nbsp;G. Fontanella ,&nbsp;F. Gargano ,&nbsp;F. Garufi ,&nbsp;F. Guarino ,&nbsp;D. Kyratzis ,&nbsp;H. Lima ,&nbsp;F. Loparco ,&nbsp;L. Wu","doi":"10.1016/j.astropartphys.2025.103171","DOIUrl":"10.1016/j.astropartphys.2025.103171","url":null,"abstract":"<div><div>Crystal Eye is a space-based all-sky monitor optimized for the autonomous detection and localization of transients in the 10 keV to 30 MeV energy range, a region where extensive observations and monitoring of various astrophysical phenomena are required. By focusing on the operating environment and its impact on the observation process, we optimized the detector design and assessed its scientific potential. We explored the use of novel techniques to achieve the science goals of the experiment. We assumed the orbit of a potential future mission at approximately 550 km altitude near the equatorial region with a 20° inclination. In such an orbit, the main background contributions for this kind of detector are from different particles and radiation of cosmic origin and secondaries produced by their interaction in the Earth’s atmospheric and geomagnetic environment. We studied the response of Crystal Eye detector in this background environment, using the Geant4 Monte Carlo simulation toolkit. We also calculated other detector performance parameters to estimate its scientific capabilities. The effective area and efficiency of the detector are calculated for low energy <span><math><mi>γ</mi></math></span>-ray sources and used to estimate its sensitivity to short-duration transient sources. The calculation shows a better effective area and sensitivity by several factors compared to existing instruments of similar type. A method is also developed and discussed to estimate the online transient-localization performance of the detector, suggesting a better localization precision by about an order of magnitude than those typically reported by existing <span><math><mi>γ</mi></math></span>-ray monitors. We present here the simulation study and results of an innovative detector design concept that can make a significant contribution in the multi-messenger era. Moreover, this study can be useful as a technical reference for similar future experiments.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"174 ","pages":"Article 103171"},"PeriodicalIF":2.9,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}