arXiv subjects

Yi-Qing Guo

Publications and source records attributed to Yi-Qing Guo.

At least 19 recordsLinked to original sources

arXiv2026

Enhanced All-Distance Equi-Zenith Angle Method for Cosmic-Ray Anisotropy Measurement

Long-term observations indicate that the relative intensity of cosmic-ray anisotropy remains below $0.1\%$ for energies less than $\sim 1$ PeV. Measuring such faint signals poses a significant challenge in data analysis, requiring careful removal of instrumental and atmospheric artifacts. The all-distance equi-zenith angle method is widely employed to extract cosmic-ray anisotropies, as it effectively suppresses the instantaneous variations arising from the instrument and atmosphere. \textcolor{black}{However, instability in the detector efficiency makes precise measurements of anisotropy challenging with this method.} In this work, we present an enhanced all-distance equi-zenith angle method for cosmic-ray anisotropy measurement. Unlike previous implementations, our improved approach enables the simultaneous measurement of anisotropies over multiple time frames and allows the detection efficiency to be determined directly from the data. This feature makes the method especially suitable for applications where the detector array does not operate with long-term stability\textcolor{black}{, and thus allows for the measurement of anisotropy with high-precision}. Moreover, our enhanced method is also feasible when the data do not span complete tropical years.

astro-ph.HE↗

arXiv2026

Co-evolution of cosmic ray energy spectra, composition, and anisotropies

The origin of cosmic rays remains an unresolved fundamental problem in astrophysics. The synergy of multiple observational probes, including the energy spectra, the mass composition, and anisotropy is a viable way to jointly uncover this mystery. In this work, we propose that the energy-dependent of those observables in a wide energy range, from $O(10)$ GeV to ultrahigh energies of $10^{11}$ GeV, share quite a few correlated features, indicating a strong co-evolution which could be a consequence of the underlying origin of different source populations. We decipher these structures with a four-component model, i.e., the ensemble of Galactic sources, a local source close to the solar system, and the ensemble of two extra-galactic source populations. In this scenario, the $O(10^2)$ GV hardening and $O(10)$ TV bump is due to the contribution of the local source, the knee is due to the maximum acceleration energy of protons by the Galactic source population, the second knee is due to the maximum acceleration energy of iron nuclei by Galactic sources, the dip feature between the two knees is due to the appearance of the extra-galactic component, the ankle comes from the transition from one extra-galactic component to the other, and the spectral suppression at the highest energies arises from the acceleration limit of the second extra-galactic component. The transition from Galactic to extra-galactic origin of cosmic rays occurs around $O(10^8)$ GeV, which is smaller than the ankle energy.

astro-ph.HE↗

arXiv2026

Two kinds of Galactic source populations could explain the cosmic-ray observation up to the "knee" region

Observations of diffuse gamma rays above hundreds of TeV from the Galactic disk provide strong evidence for the existence of PeV cosmic-ray accelerators--so-called PeVatrons--in the Galaxy. However, mounting observations have ruled out most supernova remnants as likely PeVatron candidates, suggesting instead that multiple populations of cosmic-ray sources exist in the Galaxy. Recently, the LHAASO collaboration reported the detection of ultra-high-energy gamma rays from microquasars, establishing that the black holes in these systems, which accrete matter from companion stars, are powerful PeV particle accelerators. In this work, we propose a two-component source model to explain the observed cosmic-ray spectra and composition up to the PeV range. Below approximately 100 TeV, supernova remnants serve as the dominant sources; above this energy, microquasars are considered the primary candidate population. Within this scenario, the assumption of a charge-dependent cutoff well accounts for the latest measurements, including the proton and helium spectra up to the PeV range, the energy-dependent composition, and the all-particle spectrum. In contrast, the nuclei-dependent cutoff hypothesis is ruled out by the data.

astro-ph.HE↗

arXiv2026

Detection of afterglow emission up to 100 GeV through a stacking analysis of gamma-ray bursts

High-energy gamma-ray (>GeV) emission of gamma-ray bursts (GRBs) is very important in probing the jet evolution and particle acceleration of GRBs. The observations of high-energy photons are limited except for a few very bright GRBs, hindering precise measurements of the spectral and temporal evolutions of GRBs. Here we report the detection of high-energy gamma-ray emission up to 100 GeV with Fermi-LAT using a stacking analysis of a collection of 330 GRBs. High significance detection of the emission has been found, and the precise light curves and energy spectra can be measured. The light curves and time-resolved spectra of the sub-sample of 220 LAT individually detected GRBs can be well explained by the standard afterglow emission from a population of GRBs with both synchrotron and synchrotron self-Compton mechanisms, assuming a distribution of initial Lorentz factors. However, the emission of the relatively weak sample of the 110 LAT individually undetected GRBs cannot be well reproduced in the same framework, indicating the existence of possible energy injection effect in the GeV band for the first time. The observations hence provide new insights in understanding the high-energy emission of GRBs.

astro-ph.HE↗

arXiv2026

Two-component $γ$-Ray Structure from the CR Sources Within Dense Clouds

Recent observations have revealed that several cosmic ray (CR) sources themselves exhibit pronounced double power-law features in their radiation spectra. Combined with the phenomenon of two-component structure in the observed CR energy spectrum supported by multi-messenger data, this raises a fundamental question: can the two-component structure of the cosmic ray energy spectrum and the double power-law feature of the gamma-ray radiation energy spectrum from supernova remnants be understood within a unified picture? In this study, we propose a two-component model that incorporates the re-acceleration of background ``sea" CR particles by astrophysical sources to systematically explain the formation of double power-law spectra within those sources. Our model successfully reproduces the gamma-ray observations of multiple CR sources. The results support that double power-law structures may be a generic feature of Galactic CR sources within crushed clouds. This work offers a new theoretical perspective on the origin and propagation of cosmic rays, and its predictions may be further tested with future observations of a larger sample of CR sources.

astro-ph.HE↗

arXiv2026

A Multi-messenger Search for a Nearby Microquasar Contributor to the Cosmic Ray Knee

Recently, LHAASO has detected five microquasars with high confidence, which are associated with SS 433, V4641 Sgr, GRS 1915+105, MAXI J1820+070, and Cygnus X-1, respectively. Except for Cygnus X-1, the maximum energies of gamma-ray photons emitted from these sources all exceed 100 TeV, strongly suggesting that microquasars are capable of accelerating cosmic-ray particles to energies above the PeV range. This work investigates the origin of the cosmic-ray knee region based on gamma-ray observational data from the aforementioned sources, combined with cosmic-ray proton, helium, and all-particle energy spectra, as well as anisotropy observations. Calculations indicate that these known sources contribute negligibly to the cosmic-ray knee region. However, further joint analysis reveals that a single microquasar located in a region approximately on the 2.6 kiloparsec scale in the anti-Galactic center direction can reasonably reproduce the observed cosmic-ray proton, helium, and all-particle energy spectra, as well as anisotropy features detected near Earth. We propose that this region may host one or several unidentified microquasars or similar systems, whose accelerated cosmic rays could dominate the observational characteristics of the knee region.

astro-ph.HE↗

arXiv2026

Joint constraint on the propagation origin of the cosmic-ray spectral knee from energy spectrum and anisotropy observations

The origin mechanism of the cosmic-ray knee region remains an unresolved mystery, with acceleration, interaction, and propagation models drawing significant attention. The latest experimental observations of the PeV total spectrum, composition energy spectrum, and anisotropy-particularly the precise measurements of the proton spectrum by the LHAASO experiment-have provided crucial breakthroughs in uncovering its origin. Based on the latest LHAASO measurements of the proton energy spectrum, combined with cosmic-ray spectral and anisotropy data, this study proposes that the spectral index variation in the knee region arises from changes in the propagation coefficient. By introducing a knee position $\rm \mathcal{R}_{knee}$ and an index variation $\rm δ_{knee}$, we construct a rigidity-dependent double-power-law diffusion model to reproduce the knee-region spectral structure. Through modifications to the diffusion coefficient, we successfully replicate the observed knee-region spectral structure in the LHAASO proton spectrum and calculate the corresponding anisotropy. Under current data and model dependencies, a joint analysis of the energy spectrum and anisotropy does not support the propagation origin model of the cosmic-ray knee at a 95\% confidence level. We hope that future LHAASO experiments will provide precise measurements of the energy spectra and anisotropies of various nuclei in the knee region, thereby offering a definitive test of the propagation model as the origin mechanism of the knee-region spectral structure.

astro-ph.HE↗

arXiv2025

Ultrahigh-Energy Gamma-ray Emission Associated with Black Hole-Jet Systems

Black holes (BH), one of the most intriguing objects in the universe, can manifest themselves through electromagnetic radiation initiated by the accretion flow. Some stellar-mass BHs drive relativistic jets when accreting matter from their companion stars, forming microquasars. Non-thermal emission from the radio to tera-electronvolt (TeV) gamma-ray band has been observed from microquasars, indicating the acceleration of relativistic particles. Here we report detection of four microquasars (SS 433, V4641 Sgr, GRS 1915+105, MAXI J1820+070) of spectrum extending to the ultrahigh-energy (UHE; photon energy $E>100$ TeV) band and one microquasar (Cygnus X-1) of spectrum approaching 100 TeV, using the Large High Altitude Air Shower Observatory (LHAASO). Notably, the total emission associated with SS 433 cannot be interpreted with a single leptonic component. In the UHE band, its emission is in spatial coincidence with a giant atomic cloud, which is consistent with a hadronic origin. An elongated source is discovered from V4641 Sgr with the spectrum continuing up to 800 TeV. The detection of UHE gamma rays demonstrates that accreting BHs and their environments can operate as extremely efficient accelerators of particles out of 1 peta-electronvolt (PeV), suggesting microquasars to be important contributors to Galactic cosmic rays especially around the `knee' region.

astro-ph.HE↗

arXiv2025

Investigating the signs of evolutionary characteristics in the energy spectrum of shock wave acceleration

Under ideal conditions, the theory of shock acceleration for cosmic rays predicts that different elements should exhibit strictly identical spectral indices when accelerated to the same rigidity (R). However, recent high-precision measurements of elemental energy spectra have definitively established the existence of variations in spectral indices across different elements. This study constrains the spectral indices of cosmic-ray elements using AMS-02 and DAMPE observations within the Spatially Dependent Propagation (SDP) model. For elements with A/Z = 2, spectral indices shows significant positive correlations with both atomic number Z and mass number A, likely due to A or Z-dependent fragmentation cross-sections. Predictions indicate that the observed spectra of Ni and Zn will align with the Fe spectrum, while their injection spectra will exhibit slightly softer spectral indices compared to Fe. Future observations from AMS-02, DAMPE and HERD are expected to verify these findings, while theoretical models are needed to systematically explain this phenomenon.

astro-ph.HE↗

arXiv2025

Two-component diffuse Galactic gamma-ray emission revealed with Fermi-LAT

The enigma of cosmic ray origin and propagation stands as a key question in particle astrophysics. The precise spatial and spectral measurements of diffuse Galactic gamma-ray emission provide new avenues for unraveling this mystery. Based on 16 years of Fermi-LAT observations, we find that the diffuse gamma-ray spectral shapes are nearly identical for low energies (below a few GeV) but show significant dispersion at high energies (above a few GeV) across the Galactic disk. We further show that the diffuse emission can be decomposed into two components, a universal spectral component dominating at low energies which is consistent with the expectation from interactions of background cosmic rays and the interstellar matter, and a spatially variant component dominating at high energies which is likely due to local accelerators. These findings suggest that there is dual-origin of the Galactic diffuse emission, including the ``cosmic ray sea'' from efficient propagation of particles and the ``cosmic ray islands'' from inefficient propagation of particles, and thus shed new light on the understanding of the propagation models of Galactic cosmic rays.

astro-ph.HE↗

arXiv2025

Geminga: A Window into the Role Played by the Local Halo in the Cosmic-Ray Propagation Process

A novel phenomenon among the recently observed Geminga pulsar halo is the presence of distinct radiation morphology at high energies, while no extended radiation is detected in the 10-500 GeV energy band within a $40\degree\times40\degree$ region. This phenomenon suggests that pulsar halos play a crucial role in the local propagation of cosmic rays, making it necessary to investigate the underlying mechanisms of this phenomenon. This work focuses on the 3D propagation study of cosmic rays, incorporating the Geminga pulsar into our propagation framework to investigate its contribution to different observational spectra. We consider Geminga a dominant local source of positrons, partially reproducing the observed positron spectrum and multi-wavelength radiative spectra of the Geminga halo. Through calculations of signal and background at different angles, we find that: (1) The slow-diffusion properties near the Geminga pulsar and its proper motion may cause the radiation from electrons originating from Geminga to be distributed across a more extended region. (2) The incomplete subtraction of radiation from the local halo may contribute, to some extent, to the diffuse gamma ray fluctuations detected by LHAASO. We hope that LHAASO will detect more sources of cosmic ray halo to further validate our model.

astro-ph.HE↗

arXiv2025

Exploring the Frontiers of Cosmic Ray Physics: Perspectives on GRANDProto300 and the GRAND Project

The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned large-scale radio array designed to detect ultra-high-energy cosmic rays (UHECRs, $E > 100$ PeV) and neutrinos. Employing cost-effective antennas distributed across vast areas, GRAND is optimized to observe the rare flux of ultra-high-energy particles with high precision. The GRANDProto300 (GP300) pathfinder array, currently under deployment, targets the $10^{16.5} - 10^{18}$ eV range and is anticipated to achieve approximately 15\% energy resolution and 20g/cm$^2$ $X_{\mathrm{max}}$ precision. This level of precision enables accurate measurements of the fine structure of the energy spectrum, mean logarithmic mass ($\langle \ln A \rangle$), and proton flux within this range. After five years of data collection, the sensitivity for detecting anisotropy could reach $5 \times 10^{-3}$ for energies below $10^{17.1}$ eV. With its substantially larger effective area, GRAND extends these capabilities to the highest energies ($\sim 10^{20}$ eV), offering enhanced statistics and sensitivity for spectral, composition, and anisotropy measurements within one year for UHECRs.

astro-ph.HE↗

arXiv2025

A Possible Common Physic Picture Reflected by the Gamma Ray Emission of the Galactic Center

Long-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the Galactic center exhibits a double power-law structure. In this study, we propose a new explanation for this phenomenon. We suggest that the low-energy (GeV) power-law spectrum originates from interactions between trapped background ``sea" cosmic ray particles and the dense gaseous environment near the Galactic center. In contrast, the bubble-like structure in the high-energy (TeV) spectrum is produced by protons accelerated during active phases of the Galactic center, through the same physical process. Based on this framework, we first calculate the gamma-ray emission generated by cosmic ray protons accelerated in the Galactic center. Then, using a spatially-dependent cosmic ray propagation model, we compute the energy spectrum of background ``sea" cosmic ray protons and their associated diffuse gamma-ray emission in the Galactic center region. The results closely reproduce the observations from Fermi-LAT and HESS, suggesting that their long-term data support this picture: high-energy cosmic rays in the local region originate from nearby cosmic ray sources, while low-energy cosmic rays are a unified contribution from distant cosmic ray sources. We predict that some extended Galactic sources, which remain undetectable in the GeV energy range, may become observable in the TeV range. We hope that future observations will detect more such sources, allowing us to further test and validate our model.

astro-ph.HE↗

arXiv2025

Unveiling the Mechanisms of Electron Energy Spectrum Evolution

The electron spectrum exhibits a complex structure and has controversially proposed origins. This work reproduce the evolution of the electron spectrum based on a spatially dependent propagation (SDP) model. The key point is that our SPD model features two diffusion regions leading to two diffusion timescales, competing with the cooling timescale. This results in a three-segment power-law electron spectrum: (1) The spectrum below tens of GeV is primarily influenced by cooling effects from distant sources. (2) The spectrum dominated by diffusion effects from nearby sources from tens of GeV to TeV. (3) The spectrum above TeV, which is predominantly governed by cooling effects from nearby sources. This evolution is unique to the SDP model, and we offer a comprehensive and clear depiction of electron evolution under a single propagation scenario for the first time.

hep-ph↗

arXiv2024

A Universal Energy Relation between synchrotron and Synchrotron Self-Compton radiation in GRBs and Blazars

The recent and brightest GRB 221009A observed by LHAASO marked the first detection of the onset of TeV afterglow, with a total of 7 GRBs exhibiting very high energy (VHE) afterglow radiation. However, consensus on VHE radiation of GRBs is still lacking. Multi-wavelength studies are currently a primary research method for investigating high-energy $γ$-ray astronomy. The limited sample of VHE GRBs, combined with their transient nature, hinders the progress of physical studies of GRBs. This paper aims to obtain useful information for GRB research through the properties of blazars, which share significant similarities with GRBs. By fitting high-quality and simultaneous multiwavelength spectral energy distributions with a one-zone leptonic model, the study explores the similarity of radiation properties of blazars and GRBs. A tight correlation between synchrotron and synchrotron self-Compton (SSC) emission luminosities suggests that blazars and GRBs share similar radiation mechanisms, to be specific, synchrotron radiation produces the observed X-ray photons, which also serve as targets for electrons in the SSC process. We hope that ground-based experiments can observe more GRBs in sub-TeV to confirm these findings.

astro-ph.HE↗

arXiv2024

New Insights on Gamma-Ray Burst Radiation Mechanisms from Multiwavelength Observations

The study of high-energy gamma-ray emission from gamma-ray bursts (GRBs) involves complex synchrotron radiation and synchrotron self-Compton scattering (SSC) mechanisms with multiple parameters exhibiting a wide distribution. Recent advancements in GRB research, particularly the observation of very high energy (VHE, $\rm >100~GeV$) radiation, have ushered in a new era of multiwavelength exploration, offering fresh perspectives and limitations for understanding GRB radiation mechanisms. This study aimed to leverage VHE observations to refine constraints on synchrotron + SSC radiation from electrons accelerated by forward shocks. By analyzing two external environments - the uniform interstellar medium and stratified stellar wind medium, we conducted spectral and variability fitting for five specific bursts (GRB~180720B, GRB~190114C, GRB~190829A, GRB~201216C, and GRB~221009A) to identify the optimal parameters characterizing these events. A comparative analysis of model parameter distributions with and without VHE radiation observations reveals that the magnetic energy equipartition factor $ε_B$ is more concentrated with VHE emissions. This suggests that VHE emissions may offer greater constraints on this microphysical parameter. Additionally, we found that the energy budget between VHE and keV-MeV $γ$-ray emissions under the SSC radiation exhibits an almost linear relationship, which may serve as a tool to differentiate radiation mechanisms. We anticipate future statistical analyses of additional VHE bursts to validate our findings.

astro-ph.HE↗

arXiv2024

Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model

The spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating anisotropy in the direction perpendicular to the galactic disk, which is discrepant with current observations. Thus, it is necessary to further investigate the effect of the solar offset on anisotropy. In this work, to the best of our knowledge, this is the first time that the combined studies of the solar offset, nuclei spectra, and anisotropy have been performed based on the SDP model. As a result, to reproduce CR spectra and anisotropy, the thickness of the inner halo $ (Z_{IH})$ needs to increase linearly with the displacement of the Sun. We also know that the PeV anisotropy could be used to estimate the value of the diffusion coefficient, thus breaking the degeneracy between the diffusion coefficient and halo thickness. Therefore, it is a good approach to constrain the halo thickness. Moreover, the anisotropy in the PeV energy region, as a new probe, might also shed new light on constraining the solar offset. It is hoped that the anisotropy of the energies from $\rm \sim$TeV to $\rm PeV$ can be finely measured with the LHAASO experiment, leading to a better understanding of the thick halo.

astro-ph.HE↗

arXiv2024

Contribution of the Cygnus bubble to the Galactic cosmic ray spectrum and diffuse $γ$-ray emissions

Since the discovery of cosmic rays (CRs) over a century ago, their origin has remained a mystery and a key research question. Recently, the LHAASO experiment identified the first CR super-acceleration source, the Cygnus bubble, which can accelerate CRs to energies exceeding 10 PeV. A pertinent question is: how much does the Cygnus bubble contribute to the CR spectrum observed on Earth? With the aim of answering that question, a 3D propagation analysis was conducted on CRs in this study. The Cygnus bubble was incorporated into our propagation model in order to determine its contributions to the observed spectra. First, we calculated the spectrum and spatial morphology of the Cygnus bubble to reproduce the observed LHAASO data. Subsequently, we calculated the diffuse $γ$-ray emissions produced by the CRs from the Cygnus bubble and the energy spectrum of the cosmic ray particles near Earth after propagation. Finally, we utilized a CR spatial-dependent propagation model to calculate the large-scale CR energy spectrum and the resulting diffuse $γ$-ray emissions. Our results indicate that: (1) the Cygnus bubble contributes minimally to the CR spectrum observed on Earth, (2) the emissions produced by the CR particles from the Cygnus bubble dominates the diffuse $γ$-ray emissions in that region, (3) the structural fluctuations of the diffuse $γ$-ray emissions observed by LHAASO are likely due to the local CR halo. We anticipate that LHAASO will identify more CR halo sources to validate our model.

astro-ph.HE↗