Accurate spectral analysis of high-energy astrophysical sources often relies on comparing observed data to incident spectral models convolved with the instrument response. However, for Gamma-Ray Bursts and other high-energy transient events observed at high count rates, significant distortions (e.g., pile-up, dead time, and large signal trailing) are introduced, complicating this analysis. We present a method framework to address the model dependence problem, especially to solve the problem of energy spectrum distortion caused by instrument signal pile-up due to high counting rate and high-rate effects, applicable to X-ray, gamma-ray, and particle detectors. Our approach combines physics-based Monte Carlo (MC) simulations with a model-independent spectral inversion technique. The MC simulations quantify instrumental effects and enable correction of the distorted spectrum. Subsequently, the inversion step reconstructs the incident spectrum using an inverse response matrix approach, conceptually equivalent to deconvolving the detector response. The inversion employs a Convolutional Neural Network, selected for its numerical stability and effective handling of complex detector responses. Validation using simulations across diverse input spectra demonstrates high fidelity. Specifically, for 27 different parameter sets of the brightest gamma-ray bursts, goodness-of-fit tests confirm the reconstructed spectra are in excellent statistical agreement with the input spectra, and residuals are typically within ± 2σ. This method enables precise analysis of intense transients and other high-flux events, overcoming limitations imposed by instrumental effects in traditional analyses.

The Gravitational wave burst high-energy Elec?tromagnetic Counterpart All-sky Monitor (GECAM) utilizes a large number of LaBr3 and NaI(Tl) crystals as sensitive materials for its gamma-ray detectors. To address the fitting issues of the energy resolution curves in the ground calibration of the GECAM detectors, this work conducts a comprehensive testing and comparative study of the energy resolution of 1-inch LaBr3(Ce,Sr) and NaI(Tl) crystals produced from the same batch. We employed a Hard X-ray Calibration Facility (HXCF), a PMT single-photoelectron calibration system, and Geant4 Monte Carlo simulation tools to quantify seven factors influencing energy resolution. The results indicate that the contributions of various components to energy resolution differ, with pho?toelectron statistical fluctuations and intrinsic resolution being predominant. For 100 keV X-rays, the total energy resolution of the LaBr3(Ce,Sr) crystal is 3.71

The solar flare is the primary source of eruptions that generate space weather. Its high-speed jet is believed to produce the potential termination shock (TS) at the apex of the magnetic flux loop. Within the solar atmosphere, it becomes particularly intriguing to explore the fundamental mechanisms responsible for the initial acceleration of particles and their role in the generation of solar energetic particles (SEPs), extending to the phenomenon known as ground level enhancement (GLE). This study focuses on uncovering the relationship between GLE events and the flare-TS. To achieve this, we employ a Dynamic Monte Carlo (DMC) simulation technique to model the behavior of the flare-TS. In this theoretical framework, thermal particles that are part of the high-speed outflow from magnetic reconnection events penetrate the shock front at the loop top. Through numerous cycles of interaction with the TS, these particles undergo successive energy gains. Consequently, our simulation reveals details of the energy spectral structure. Besides the standard power-law with a hard index below 2 MeV, the emergence of a "bump-on-tail" structure between 2 and 20 MeV is observed in the simulated accelerated protons. Additionally, the efficiency of the TS acceleration dependent on the speed of the input bulk flow suggests a potential SEPs source for boosting GLEs. Based on these findings, we suggest that the termination shock acceleration mechanism serves as an initial source of energetic particles, which would lead to GLEs directly or seed the subsequent interplanetary processes for GLEs indirectly.

The primary scientific objective of the High Energy Burst Searcher (HEBS) is to serve as a crucial component of the global space monitoring network for high-energy celestial burst sources. HEBS aims to monitor the high-energy electromagnetic counterparts of gravitational wave events, as well as the high-energy radiation from rapid radio bursts, gamma-ray bursts, magnetar flares, and other high-energy celestial phenomena across the entire sky. This effort will provide essential data support for related physical research, including energy spectra, light curves, and positional information. The probe is deployed on the Satech-01 satellite and operates in a 500 km solar-synchronous orbit. HEBS is equipped with two types of detectors: the Gamma Ray Detector (GRD) and the Charged Particle Detector (CPD). The GRD employs lanthanum bromide crystals coupled with silicon photomultiplier (SiPM) technology, as well as sodium iodide crystals paired with SiPM technology, to detect X-rays and gamma rays in the energy range of 6 keV to 5.9 MeV. It enables the localization of gamma-ray bursts and other high-energy events through the coordinated detection of multiple probes oriented in different directions. The CPD utilizes plastic scintillator technology coupled with SiPM to detect charged particles within the energy range of 150 keV to 5 MeV. When combined with the GRD, it effectively identifies and distinguishes space particle events from actual celestial phenomena. The payload processor (Electronics Box, EBOX) features onboard triggering and positioning capabilities, transmitting trigger times and positional data via Beidou short messaging in quasi-real time. This information will guide other telescopes in conducting follow-up observations.

This study aims to provide an accurate estimation of the intrinsic resolution of LaBr3(Ce) crystal through a combination of experimental and simulation methods. We re-analyzed the data from previous Wide-Angle Compton Coincidence (WACC) and Hard X-ray Calibration Facility (HXCF) experiments, conducted PMT Single-Photoelectron Calibration (SPEC) and radial non-uniformity (also called Spot Scanning, SS) experiments to acquire new data, and combined these results with Geant4 simulations to isolate the contribution of each physical process to the total energy resolution, thereby allowing for a precise estimation of the scintillator's intrinsic resolution. For 100 keV Xrays, the total energy resolution of LaBr3(Ce) crystal is 3.99% +/- 0.04% (expressed as 1-sigma), with statistical fluctuations and intrinsic resolution as the main components, contributing 2.47% +/- 0.00% and 3.06% +/- 0.06%, respectively. We identify two main sources of intrinsic resolution: one primarily due to non-proportional scintillation, contributing 2.28% +/- 0.00%, and the other due to fluctuations in the energy transfer process, contributing 2.04% +/- 0.08%. We quantified six components of the total energy resolution and reconstructed the photon response using Geant4. The consistency between the reconstructed relative light yield and the experimental measurements validated the mass model of the LaBr3(Ce) detector used in the simulations.

The central position of the South Atlantic Anomaly (SAA) has been drifting westward or northward, and the drift speeds exhibit a complex relationship with solar activity, which also affects the area of the SAA configuration. Using six years of data from the low-Earth orbit satellite CSES, we analyze the spatiotemporal evolution of the geomagnetic field and high-energy protons within the SAA during Solar Cycle 25. Low-energy protons (2.0–10.0 MeV) exhibit a characteristic double-peak structure, whereas high-energy protons (10.0–20.0 MeV) display a single-peak profile—consistent with observations from NOAA/MEPED. By fitting a Double-Gaussian distribution in both latitude and longitude from January 2019 to April 2024, we find that the center of the SAA proton distribution drifted northward at an average speed of 0.29±0.12°/yr (dayside). At the same time, the SAA proton center drifted westward at speeds of 0.36±0.08°/yr (dayside) and 0.33±0.10°/yr (nightside). Notably, lower-energy protons drift slightly faster. The geomagnetic field variations in the SAA region observed by CSES are generally consistent with the IGRF-13 model. Based on IGRF-13, we calculate drift speeds from 2015 to 2025 to be 0.014±0.002°/yr in the northward (latitudinal) direction and 0.282±0.030°/yr in the westward (longitudinal) direction. Quantitative boundary analysis further indicates that the area of the SAA decreased by 6.09

Gamma-Ray Transient Monitor (GTM) is an all-sky monitor onboard the Distant Retrograde Orbit-A (DRO-A) satellite, with the scientific objective of detecting gamma-ray bursts in the energy range of 20 keV to 1 MeV. GTM is equipped with five Gamma-Ray Transient Probes (GTPs), utilizing NaI(Tl) scintillators coupled with silicon photomultiplier (SiPM) arrays for signal readout. To test the performance of the GTP in detecting electrons, we used the IHEP Electron-Beam Facility (a continuous-energy-tunable, low-current, quasi-single-electron accelerator) for ground-based electron tests of the GTP. This paper provides a detailed description of the operating principles of the electron accelerator and presents the process and results of the GTP electron-beam tests. The test results show that the GTP has a dead time of less than 4 μs for normal signals and approximately 70 μs for overflow signals, consistent with the design specifications. The time-recording capability of the GTP was tested and found to be normal, with accurate recording of overflow events. The GTP's response to electrons in the 0.4-1.4 MeV range is also normal. Additionally, we used Geant4 to simulate the GTP's energy response and performed a comparative analysis of the simulation and experimental results. The performance tests and ground-based electron calibration validated the design of the GTP and enhanced the GTP's mass model, laying the foundation for payload development, in-orbit observation strategies, and scientific data analysis.

Two major solar eruptions on AR 12673 produced a Forbush decrease (FD) event (reduction of cosmic rays) on 2017 September 8 and ground-level enhancement (GLE; enhancement of cosmic rays) on 2017 September 10. The occurrence of two contrasting cosmic-ray events within 2 days that are associated with two similar X-class solar flares (X9.3 and X8.2) and share the same active region on the Sun provides us a rare opportunity to understand the dominant factors in determining the properties of transient cosmic-ray events. Using a suite of modern-day instruments continuously tracking solar eruptions from the Sun to the Earth with ground-based cosmic-ray detectors, we reveal the complete cause–effect chain of activities for these two events. We conclude that the different consequences on the ground arise from two effects of the eruptions near the Sun: (1) the geometric effect of CMEs and (2) the intensity effect of CME-driven shocks. The first eruption, which originated at the heliographic longitude of W34° on 2017 September 6, had its CME ejecta and CME-driven shock intercept the Earth, leading to the FD event. The second eruption, which occurred on September 10 at W88°, only had its far flank reach the Earth. The peak shock speed of 3344 km s −1 of the second eruption, much faster than the 2175 km s −1 of the first eruption, is the dominant factor producing the GLE event, even though the first eruption is better connected magnetically to the Earth and has a similar flare. The results indicate that the production of GLE particles can be dominated by fast-enough CME-driven shocks.

Gamma-ray Transient Monitor (GTM) is an all-sky monitor onboard the Distant Retrograde Orbit-A (DRO-A) satellite with the scientific objective of detecting gamma-ray transients ranging from 20 keV to 1 MeV. GTM is equipped with 5 Gamma-ray Transient Probe (GTP) detector modules, utilizing the NaI(Tl) scintillator coupled with a SiPM array. To reduce the SiPM noise, GTP makes use of a dedicated dual-channel coincident readout design. In this work, we firstly studied the impact of different coincidence times on detection efficiency and ultimately selected the 500 ns time coincidence window for offline data processing. To test the performance of GTPs and validate the Monte Carlo simulated energy response, we conducted comprehensive ground calibration tests using Hard X-ray Calibration Facility (HXCF) and radioactive sources, including energy response, detection efficiency, spatial response, bias-voltage response, and temperature dependence. We extensively presented the ground calibration results, and validated the design and mass model of GTP detector. These work paved the road for the in-flight observation and science data analysis.

Realtime trigger and localization of bursts are the key functions of GECAM, an all-sky gamma-ray monitor launched on 2020 December 10. We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box. This onboard software has the following features: high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation, dedicated localization algorithm optimized for both short and long bursts, and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system. This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM. It covers the general design, workflow, the main functions, and the algorithms used in the system. The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube, as well as an overview of the performance for real celestial bursts during its in-orbit operation.

The GECAM series of satellites utilizes LaBr _3 (Ce), LaBr _3 (Ce,Sr), and NaI(Tl) crystals as sensitive materials for gamma-ray detectors (GRDs). To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E–C relationship, comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons, radioactive sources, and mono-energetic X-rays. The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences, with all three crystals presenting a higher nonlinearity for X/ γ -rays than for Compton electrons. Despite the LaBr _3 (Ce) and LaBr _3 (Ce,Sr) crystals having higher absolute light yields, they exhibited a noticeable nonlinear decrease in the light yield, especially at energies below 400 keV. The NaI(Tl) crystal demonstrated an "excess" light output in the 6–200 keV range, reaching a maximum "excess" of 9.2

The development of multimessenger astrophysics allows us to probe various background particles from the distant early universe. Up to now, much effort has been made researching the emission and radiation of diverse steady or transient astrophysical sources. We review the potential accelerating, escaping, propagating, and radiation process of high-energy particles under specific circumstances for regular astrophysical sources and briefly discuss the underlying contribution from their emissions to the intensity of ultrahigh-energy cosmic ray, TeV-PeV cosmic neutrino, and the diffuse gamma-ray background, aiming to find a possible common origin.

ABSTRACT As the main detector of the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor mission (GECAM), the calibration of the energy response and detection efficiency of the gamma-ray detector (GRD) is the main content of the ground-based calibration. This article mainly focuses on the calibration of the energy response and detection efficiency in the 8–160 keV with a refined measurement around the absorption edges of the lanthanum bromide crystal ($\rm {LaBr_3}$). The GRD performances for different crystal types, data acquisition modes, working modes, and incident positions are also analysed in detail. We show that the calibration campaign is comprehensive, the detector performance meets the flight requirements, and the calibration results generally agree with simulations as expected. The detector’s model was corrected by the ground-based calibration, which led to the establishment of the calibration data base.

For the first time, we use the Event Horizon Telescope (EHT) data to constrain the parameters of braneworld black holes which constrain $\epsilon>-0.0655>-0.1218$ for the Anisotropic black hole and $l^2=0.0745^{+0.2864+0.5156}_{-0.0745-0.0745}$ for the Garriga-Tanaka black hole. Based on the fitted data, we calculate the photon deflection, the angular separation and time delay between different relativistic images of the the anisotropic black hole and the Garriga-Tanaka black hole. And furthermore, we study the quasinormal modes (QNMs). The results shed light on existence of extra dimension.

GRB 221009A is the brightest gamma-ray burst ever detected since the discovery of this kind of energetic explosions. However, an accurate measurement of the prompt emission properties of this burst is very challenging due to its exceptional brightness. With joint observations of \textit{Insight}-HXMT and GECAM-C, we made an unprecedentedly accurate measurement of the emission during the first $\sim$1800 s of GRB 221009A, including its precursor, main emission (ME, which dominates the burst in flux), flaring emission and early afterglow, in the hard X-ray to soft gamma-ray band from $\sim$ 10 keV to $\sim$ 6 MeV. Based on the GECAM-C unsaturated data of the ME, we measure a record-breaking isotropic equivalent energy ($E_{\rm iso}$) of $\bf \sim 1.5 \times 10^{55}$ erg, which is about eight times the total rest-mass energy of the Sun. The early afterglow data require a significant jet break between 650 s and 1100 s, most likely at $\sim950$ s from the afterglow starting time $T_{AG}$, which corresponds to a jet opening angle of $\sim {0.7^\circ} \ (\eta_\gamma n)^{1/8}$, where $n$ is the ambient medium density in units of $\rm cm^{-3}$ and $\eta_\gamma$ is the ratio between $\gamma$-ray energy and afterglow kinetic energy. The beaming-corrected total $\gamma$-ray energy $E_{\gamma}$ is $\sim 1.15 \times10^{51} \ (\eta_\gamma n)^{1/4}$ erg, which is typical for long GRBs. These results suggest that this GRB may have a special central engine, which could launch and collimate a very narrowly beamed jet with an ordinary energy budget, leading to exceptionally luminous gamma-ray radiation per unit solid angle. Alternatively, more GRBs might have such a narrow and bright beam, which are missed by an unfavorable viewing angle or have been detected without distance measurement.

This study aims to provide an accurate estimation of the intrinsic resolution of LaBr_3(Ce) crystal through a combination of experimental and simulation methods. We re-analyzed the data from previous Wide-Angle Compton Coincidence (WACC) and Hard X-ray Calibration Facility (HXCF) experiments, conducted PMT Single-Photoelectron Calibration (SPEC) and radial non-uniformity (also called Spot Scanning, SS) experiments to acquire new data, and combined these results with Geant4 simulations to isolate the contribution of each physical process to the total energy resolution, thereby allowing for a precise estimation of the scintillator's intrinsic resolution. For 100 keV X-rays, the total energy resolution of LaBr_3(Ce) crystal is 3.99 1-σ), with statistical fluctuations and intrinsic resolution as the main components, contributing 2.47 We identify two main sources of intrinsic resolution: one primarily due to non-proportional scintillation, contributing 2.28 due to fluctuations in the energy transfer process, contributing 2.04 0.08 reconstructed the photon response using Geant4. The consistency between the reconstructed relative light yield and the experimental measurements validated the mass model of the LaBr_3(Ce) detector used in the simulations.

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) monitors gamma-ray bursts (GRBs) coincident with gravitational wave events over the whole sky. It also monitors other burst events, such as the high-energy radiation of fast radio bursts, various GRBs, and magnetar bursts. GECAM can measure the energy spectra, light curves, and location of all kinds of bursts. GECAM consists of two small satellites which operate in the same low earth orbit but in opposite geocentric directions. To obtain an all-sky field of view, the two satellites operate in opposite orbital phases. The GECAM payload includes two kinds of detectors: charged particle detector (CPD) and gamma-ray detector (GRD). Each GRD module consists of a LaBr3:Ce scintillator and a SiPM array, and its gamma-ray detection range is 5 keV-5 MeV. GECAM retrieves the locations of events such as GRBs through analyzing the data of the multiple GRDs on both satellites. Meanwhile, the CPD consists of a plastic scintillator and a SiPM array that detects charged particles of energies from 300 keV to 5 MeV. The GECAM distinguishes the charged particle burst events in space by jointly analyzing the GRD and CPD data. The payload electronic box (EBOX) provides in-flight trigger and burst localization. The trigger and burst location data are transmitted by a BeiDou Short Message system, which allows GECAM to guide other telescopes to do follow-up observations.

The China Seismo-Electromagnetic Satellite(CSES) will investigate iono-magnetospheric disturbance and will monitor the temporal stability of the inner Van Allen radiation belts.In particular,the mission aims at confirming the existences of a temporal correlation between the occurrence of earthquakes and the observation of electromagnetic disturbances, plasma fluctuations and anomalous fluxes of high-energy particles precipitating from the inner Van Allen belt in space.The high energy detector of the High Energy Particle Package(HEPP-H) is a payload onboard CSES and is designed for detecting electrons(2–50 MeV) and protons(20–200 MeV) in its 500 km orbit above Earth.CSES was launched in February 2018.In this paper, the instrumentation and development of the HEPP-H calorimeter are described.The calibration with beam particles(electrons and protons) is discussed in detail.

A cosmic-ray muon telescope has been collecting data since the end of 2014, which was shortly after the telescope was built in the Zhongshan Station of Antarctica. The telescope is the first observation device to be built by Chinese scientists in Antarctica. The pressure change is very strong in Zhongshan station. The count rate of the pressure correction results shows that the large variations in the count rate are likely caused by pressure fluctuations. During the period from 18 June to 22 June 2015, four halo coronal mass ejections (CMEs) were ejected from the Sun. These CMEs initiated a series of Forbush decreases (FD) when they reached the Earth. We conducted a comprehensive study of the intensity fluctuations of galactic cosmic rays recorded during FDs. The intensity fluctuations used in this study were collected by cosmic ray detectors of multiple stations (Zhongshan, McMurdo, South Polar, and Nagoya), and the solar wind measurements were collected by ACE and WIND. The profile of the FD of 22 June demonstrated a four-step decrease. The traditional one- or two-step FD classification method does not adequately explain the FD profile results. The interaction between the faster CME that occurred on 21 June 2015 and the two slow CMEs of the earlier few days should be considered. The cosmic ray intensities of the South Pole, McMurdo, and Zhongshan stations have similar hourly variations, whereas the galactic cosmic rays recorded between polar and non-polar locations are distinct. The FD pre-increase of 22 June 2015 for the Nagoya muon telescope (non-polar location) lags those of the McMurdo and Zhongshan stations (polar locations) by 1 h. The FD onset of 22 June 2015 for the Nagoya muon telescope lags those of the polar locations by 1 h.

By the end of 2014, a cosmic ray muon telescope was installed at Zhongshan Station in Antarctic and has been continuously collecting data since then. It is the first surface muon telescope to be built in Antarctic. In June 2015, five CMEs were ejected towards the Earth initiating a big large Forbush decrease (FD) event. We conduct a comprehensive study of the galactic cosmic ray intensity fluctuations during the FD using the data from cosmic ray detectors of multiple stations (Zhongshan, McMurdo, South Polar and Nagoya) and he solar wind measurements from ACE and WIND. A pre-increase before the shock arrival was observed. Distinct differences exist in the timelines of the galactic cosmic ray recorded by the neutron monitors and the muon telescopes. FD onset for Zhongshan muon telescope is delayed (2.5h) with respect to SSC onset. This FD had a profile of four-step decrease. The traditional one- or two-step classification of FDs was inadequate to explain this FD.