Astroparticle Physics最新文献

{"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":"2026-02-01","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":"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":"2026-02-01","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":"Camera calibration of the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory","authors":"Franca Cassol ,&nbsp;Maximilian Linhoff ,&nbsp;Yukiho Kobayashi ,&nbsp;Julian Sitarek ,&nbsp;Pawel Gliwny ,&nbsp;Shunsuke Sakurai ,&nbsp;Maurizio Iori ,&nbsp;Michele Palatiello ,&nbsp;Seiya Nozaki ,&nbsp;Takayuki Saito","doi":"10.1016/j.astropartphys.2025.103189","DOIUrl":"10.1016/j.astropartphys.2025.103189","url":null,"abstract":"<div><div>The Cherenkov Telescope Array Observatory (CTAO), a forthcoming very-high-energy gamma-ray facility, will use the Imaging Atmospheric Cherenkov Technique (IACT) to achieve unprecedented energy and angular resolution from 20 GeV to 300 TeV. Large-Sized Telescopes (LSTs) are crucial for the low-energy range. This paper details the calibration tools and methods developed for the first LST (LST-1) to ensure the precise conversion of photomultiplier tube signals and accurate photon timing, vital for the reconstruction of extensive air showers. This framework supports LST-1’s early science and will be applied to future LSTs.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103189"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617883","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":"2026-02-01","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":"Uncertainties in the estimation of air shower observables from Monte Carlo simulation of radio emission","authors":"Carlo S. Cruz Sanchez ,&nbsp;Patricia M. Hansen ,&nbsp;Matias Tueros ,&nbsp;Jaime Alvarez-Muñiz ,&nbsp;Diego G. Melo","doi":"10.1016/j.astropartphys.2025.103183","DOIUrl":"10.1016/j.astropartphys.2025.103183","url":null,"abstract":"<div><div>The detection of extensive air showers (EAS) induced by cosmic rays via radio signals has undergone significant advancements in the last two decades. Numerous ultra-high energy cosmic ray experiments routinely capture radio pulses in the MHz to GHz frequency range emitted by EAS. The Monte Carlo simulation of these radio pulses is crucial to enable an accurate reconstruction of the primary cosmic ray energy and to infer the composition of the primary particles. In this work, a comprehensive comparison of the predicted electric field in EAS simulated with CoREAS and ZHAireS was conducted to estimate the systematic uncertainties arising from the use of different simulation packages in the determination of two key shower observables namely, the electromagnetic energy of the EAS and the depth of maximum development (<span><math><msub><mrow><mi>X</mi></mrow><mrow><mo>max</mo></mrow></msub></math></span>). For this comparison, input parameters and settings as similar as possible were used in both simulations, along with the same realistic atmospheric refractive index depending on altitude, which is crucial for the prediction of radio emission properties of EAS. In addition, simulated EAS with very similar values of depth of maximum development were selected. Good agreement was found between CoREAS and ZHAireS, with discrepancies in the dominant electric field components generally remaining below 10% across the frequency range of a few MHz to hundreds of MHz, relevant for most radio detection experiments, translating into uncertainties in the determination of energy below 5% and <span><math><mrow><mo>≃</mo><mn>10</mn><mspace></mspace><msup><mrow><mi>g/cm</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span> in <span><math><msub><mrow><mi>X</mi></mrow><mrow><mo>max</mo></mrow></msub></math></span>. Our work underscores the need for further studies to clarify their origin and impact on <span><math><msub><mrow><mi>X</mi></mrow><mrow><mo>max</mo></mrow></msub></math></span> inference in composition analyses.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103183"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321291","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":"The source of the cosmic-ray excess in the Centaurus region—Constraints on possible candidates, mass composition and cosmic magnetic fields","authors":"Teresa Bister","doi":"10.1016/j.astropartphys.2025.103190","DOIUrl":"10.1016/j.astropartphys.2025.103190","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The most significant excess in the arrival directions of ultra-high-energy cosmic rays with energies &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;≳&lt;/mo&gt;&lt;mn&gt;40&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;EeV&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is found in the direction of several interesting source candidates, most prominently the nearby radio galaxy Centaurus A. Naturally, Centaurus A has been suspected to create the anisotropy — but very different scenarios have been proposed. This includes a subdominant source contribution in combination with isotropic background sources, as well as a scenario where Centaurus A supplies the whole cosmic-ray flux above the ankle. Recently, it was suggested that the overdensity could instead consist of strongly deflected events from the Sombrero galaxy. Thanks to the recent development of several models of the Galactic magnetic field, it is now possible to test these proposed scenarios explicitly. We find that both sources inside the overdensity region (Centaurus A, NGC 4945, or M83), as well as outside of it (Sombrero galaxy) can in principle reproduce the excess. Leveraging the measured overdensity direction, significance, angular scale, and energy evolution, we place limits on the allowed signal fraction, the possible ejected charge number and the strength of the extragalactic magnetic field between the respective source and Earth. We find that the scenario of a subdominant source in the overdensity region requires the charge number to be &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and the extragalactic magnetic field quantity &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;nG&lt;/mi&gt;&lt;msqrt&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;Mpc&lt;/mi&gt;&lt;/mrow&gt;&lt;/msqrt&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to be between &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; (depending on the charge and signal fraction). For the Sombrero galaxy to be the source, the dominant charge number has to be around &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;nG&lt;/mi&gt;&lt;msqrt&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;Mpc&lt;/mi&gt;&lt;/mrow&gt;&lt;/msqrt&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;mn&gt;20&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. We find that a scenario where all the flux above &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;30&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;EeV&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is supplied by Cen A or M83 is possible for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;20&lt;/mn&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;nG&lt;/mi&gt;&lt;msqrt&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;Mpc&lt;/mi&gt;&lt;/mrow&gt;&lt;/msqrt&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;mn&gt;30&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and a mixed composition – explaining both the Centaurus region excess and the distribution of the highest-energy events – however, another contributing source is possibly required in the energy range &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;30&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;EeV&lt;","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103190"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571527","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":"2026-02-01","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":"TXS 0506+056-like blazar sources and their role as possible neutrino emitters","authors":"I. Viale ,&nbsp;G. Principe ,&nbsp;C. Righi ,&nbsp;M. Cerruti ,&nbsp;F. Tavecchio ,&nbsp;E. Bernardini","doi":"10.1016/j.astropartphys.2025.103191","DOIUrl":"10.1016/j.astropartphys.2025.103191","url":null,"abstract":"<div><div>The interest in blazars as candidate neutrino emitters grew after the 3<span><math><mi>σ</mi></math></span> evidence for a contemporaneous joint photon and neutrino emission from the flaring blazar TXS 0506+056 in 2017. Blazars, a class of extragalactic sources with relativistic jets pointing toward Earth, present a broadband emission interpretable via leptonic and hadronic processes, the latter relevant for proton acceleration and neutrino production. Several emission models have been developed to explain this multi-messenger observation, but the details of the neutrino production and the nature of TXS 0506+056 are not yet fully understood. In this work we investigate the properties of sources similar to TXS 0506+056. We select a sample of blazars from the Fermi 4LAC-DR2 catalog by constraining a number of key parameters in ranges centered on TXS 0506+056 values. We estimate their disk accretion efficiency and model their spectral energy distribution (SED) in terms of lepto-hadronic emission, gaining information respectively on the potential similarity of their environment with that of TXS 0506+056 and on their neutrino flux and detectability prospects at TeV energies. Our study shows the candidates’ high energy emission to be dominated by leptonic processes. Part of them also show a high accretion rate, characteristic of FSRQs. For these sources, the very high energy (VHE) and neutrino fluxes appear undetectable by current and future instruments in an average emission state.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103191"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617742","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":"Multi-wavelength variability of Mrk 501 during the observations with MACE in June–July, 2022","authors":"P. Pandey ,&nbsp;B. Ghosal ,&nbsp;C. Borwankar ,&nbsp;A. Tolamatti ,&nbsp;Z.A. Dar ,&nbsp;S. Godiyal ,&nbsp;S. Godambe ,&nbsp;J. Hariharan ,&nbsp;Keshvanand ,&nbsp;N. Mankuzhyil ,&nbsp;S. Norlha ,&nbsp;D. Sakar ,&nbsp;R. Thubstan ,&nbsp;K. Venugopal ,&nbsp;A. Pathania ,&nbsp;K.K. Singh ,&nbsp;M. Khurana ,&nbsp;P. Chandra ,&nbsp;M.K. Koul ,&nbsp;S.V. Kotwal ,&nbsp;K.K. Yadav","doi":"10.1016/j.astropartphys.2025.103188","DOIUrl":"10.1016/j.astropartphys.2025.103188","url":null,"abstract":"<div><div>Mrk 501, a high synchrotron peak blazar (HBL), located at a redshift of z <span><math><mo>=</mo></math></span> 0.034, is known for its frequent flaring episodes across various energy bands. Very high energy (VHE) <span><math><mi>γ</mi></math></span>-ray emission in the energy range from 80 GeV to 3.2 TeV from Mrk 501 was detected by MACE telescope during of June–July, 2022. It is found that the VHE emission from the source remained steady during that period with an average flux value of <span><math><mrow><mrow><mo>(</mo><mn>1</mn><mo>.</mo><mn>62</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>13</mn><mo>)</mo></mrow><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup><mspace></mspace><msup><mrow><mi>ph cm</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></mrow></math></span>. An X-ray flare was detected by <em>Swift</em>-XRT in the energy range of 0.3–10 keV during the observation period. In this work, a comprehensive multi-wavelength analysis of the Mrk 501 is presented using the observations from MACE, <em>Fermi</em>-LAT, <em>Swift</em>-BAT, <em>Swift</em>-XRT and <em>Swift</em>-UVOT. The analysis is focused on characterising the X-ray variability during the observation period. Significant X-ray spectral variations were found in the source, showing spectral hardening during the X-ray flaring activity. Spectral energy distributions (SEDs) were obtained using quasi-simultaneous multi-wavelength data during both the high and low X-ray flux states. Theoretical modelling of the SEDs was done using a leptonic model. It is found that both the SEDs corresponding to the high and low X-ray flux states could be explained within the framework of a one-zone leptonic model. The study provides insights into the emission mechanisms of Mrk 501 and its role in understanding the underlying particle distribution in the source.</div></div>","PeriodicalId":55439,"journal":{"name":"Astroparticle Physics","volume":"175 ","pages":"Article 103188"},"PeriodicalIF":2.9,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416337","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":"2026-02-01","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}