arXiv subjects

Qiang Yuan

Publications and source records attributed to Qiang Yuan.

At least 55 records · Page 3Linked to original sources

arXiv2024

Galactic diffuse emission from radio to ultra-high-energy gamma rays in light of up-to-date cosmic ray measurements

Cosmic rays travel throughout the Galaxy, leaving traces from radio to ultra-high-energy gamma rays due to interactions with the interstellar gas, radiation field and magnetic field. Therefore, it is necessary to utilize multi-wavelength investigations on the Galactic diffuse emission to shed light on the physics of CR production and propagation. In this work, we present a spatially dependent propagation scenario, taking account of a local source contribution, while making allowances for an additional CR component freshly accelerated near their sources. In this picture, after reproducing the particle measurements at the Solar system, we calculated the intensity and compared the spectral energy distribution to observations from Fermi-LAT and LHAASO-KM2A in the gamma-ray band, and from WMAP and Planck among other radio surveys at lower energies. Multi-band data considered in conjunction, the former comparison exhibits sufficiently good consistency in favor of our model, while the latter calls for improvement in data subtraction and processing. From this standpoint, there remains potential for advanced observations at energies from milli-eVs to MeVs towards the Galactic plane, in order to evaluate our model further and more comprehensively in the future.

astro-ph.HE↗

arXiv2024

Prospects for Joint Detection of Gravitational Waves with Counterpart Gamma-Ray Bursts Detected by the HADAR Experiment

The detection of GW170817/GRB170817A implied the strong association between short gamma-ray bursts (SGRBs) and binary neutron star (BNS) mergers which produce gravitational waves (GWs). More evidence is needed to confirm the association and reveal the physical processes of BNS mergers. The upcoming High Altitude Detection of Astronomical Radiation (HADAR) experiment, excelling in a wide field of view (FOV) and a large effective area above tens of GeV, is a hope for the prompt detection of very-high-energy (VHE; > 10 GeV) SGRBs. The aim of this paper is to simulate and analyse GW/SGRB joint detections by future GW detector networks in synergy with HADAR, including the second generation LIGO, Virgo and KAGRA and the third generation ET and CE. We provide a brief introduction of the HADAR experiment for SGRB simulations and its expected SGRB detections. For GW simulations, we adopt a phenomenological model to describe GWs produced by BNS mergers and introduce the signal-noise ratios (SNRs) as detector responses. Following a theoretical analysis we compute the redshift-dependent efficiency functions of GW detector networks. We then construct the simulation of GW detection by Monte Carlo sampling. We compare the simulated results of LIGO-Virgo O2 and O3 runs with their actual detections as a check. The combination of GW and SGRB models is then discussed for joint detection, including parameter correlations, triggered SNRs and efficiency skymaps. The estimated joint detection rates are 0.09-2.52 per year for LHVK network with HADAR under different possible configurations, and approximately 0.27-7.89 per year for ET+CE network with HADAR.

astro-ph.HE↗

arXiv2023

Searching for axion dark matter with MeerKAT Radio Telescope

Axions provide a natural and well-motivated dark matter candidate, with the capability to convert directly to photons in the presence of an electromagnetic field. A particularly compelling observational target is the conversion of dark matter axions into photons in the magnetospheres of highly magnetised neutron stars, which is expected to produce a narrow spectral peak centred at the frequency of the axion mass. We point the MeerKAT radio telescope towards the isolated neutron star J0806.4$-$4123 for $10$-hours of observation and obtain the radio spectra in the frequency range $769$-$1051$ MHz. By modelling the conversion process of infalling axion dark matter (DM), we then compare these spectra to theoretical expectations for a given choice of axion parameters. Whilst finding no signal above $5σ$ in the data, we provide a unique constraint on the Primakoff coupling of axion DM, $g_{{\rm a}γγ}\lesssim 9.3 \times 10^{-12}\,{\rm GeV}^{-1}$ at the $95\%$ confidence level, in the mass range $3.18$-$4.35\,μ$eV. This result serves the strongest constraint in the axion mass range $4.20$-$4.35\,μ$eV.

astro-ph.CO↗

arXiv2023

Exploring dark matter spike distribution around the Galactic centre with stellar orbits

Precise measurements of the stellar orbits around Sagittarius A* have established the existence of a supermassive black hole (SMBH) at the Galactic centre (GC). Due to the interplay between the SMBH and dark matter (DM), the DM density profile in the innermost region of the Galaxy, which is crucial for the DM indirect detection, is still an open question. Among the most popular models in the literature, the theoretical spike profile proposed by Gondolo and Silk (1999; GS hereafter) is well adopted. In this work, we investigate the DM spike profile using updated data from the Keck and VLT telescopes considering that the presence of such an extended mass component may affect the orbits of the S-stars in the Galactic center. We examine the radius and slope of the generalized NFW spike profile, analyze the Einasto spike, and discuss the influence of DM annihilation on the results. Our findings indicate that an initial slope of $γ\gtrsim 0.92$ for the generalized NFW spike profile is ruled out at a 95% confidence level. Additionally, the spike radius $R_{\rm sp}$ larger than 21.5 pc is rejected at 95% probability for the Einasto spike with $α=0.17$, which also contradicts the GS spike model. The constraints with the VLT/GRAVITY upper limits are also projected. Although the GS NFW spike is well constrained by the Keck and VLT observation of S2, an NFW spike with a weak annihilation cusp may still be viable, as long as the DM annihilation cross section satisfies $\left< σv \right> \gtrsim 7.7\times 10^{-27}~{\rm cm^3\,s^{-1}} (m_{\rm DM}/100~{\rm GeV})$ at 95% level.

astro-ph.GA↗

arXiv2023

Application of Deep Learning Methods Combined with Physical Background in Wide Field of View Imaging Atmospheric Cherenkov Telescopes

The HADAR experiment, which will be constructed in Tibet, China, combines the wide-angle advantages of traditional EAS array detectors with the high sensitivity advantages of focused Cherenkov detectors. Its physics objective is to observe transient sources such as gamma-ray bursts and counterparts of gravitational waves. The aim of this study is to utilize the latest AI technology to enhance the sensitivity of the HADAR experiment. We have built training datasets and models with distinctive creativity by incorporating relevant physical theories for various applications. They are able to determine the kind, energy, and direction of incident particles after careful design. We have obtained a background identification accuracy of 98.6%, a relative energy reconstruction error of 10.0%, and an angular resolution of 0.22-degrees in a test dataset at 10 TeV. These findings demonstrate the enormous potential for enhancing the precision and dependability of detector data analysis in astrophysical research. Thanks to deep learning techniques, the HADAR experiment's observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S. at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies. Additionally, our experiment offers a fresh approach to dealing with strongly connected scattered data.

astro-ph.IM↗

arXiv2023

Galactic diffuse gamma-ray emission from GeV to PeV energies in light of up-to-date cosmic ray measurements

The diffuse gamma-ray emission between 10 and 1000 TeV from the Galactic plane was recently measured by the Large High Altitude Air Shower Observatory (LHAASO). These observations will help tremendously in constraining the propagation and interaction of cosmic rays in the Milky Way. Additionally, new measurements of CR spectra reach a very high precision up to 100 TeV energies, revealing multiple spectral structures of various species. In this work, we confront the model prediction of the diffuse gamma-ray emission, based on up-to-date measurements of the local cosmic ray spectra and simplified propagation setup, with the measurements of diffuse gamma-rays. To better constrain the low-energy part of the model, we analyze the 14.6 years of Fermi-LAT data to extract the Galactic diffuse emission between 1 and 500 GeV from the same sky regions of LHAASO, after subtracting the contribution from known sources and the isotropic diffuse gamma-ray background. The joint Fermi-LAT and LHAASO spectra thus cover a very wide energy range from 1 GeV to 1 PeV with small gaps from 0.5 to 10 TeV. Compared with the prediction, we find that clear excesses between several GeV and ~60 TeV of the diffuse emission exist. Possible reasons to explain the excesses may include unresolved sources or more complicated propagation models. We illustrate that an exponential-cutoff-power-law component with an index of -2.40 and cutoff energy of ~30 TeV is able to account for such excesses.

astro-ph.HE↗

arXiv2023

BGO quenching effect on spectral measurements of cosmic-ray nuclei in DAMPE experiment

The Dark Matter Particle Explorer (DAMPE) is a satellite-borne detector designed to measure high energy cosmic-rays and $γ$-rays. As a key sub-detector of DAMPE, the Bismuth Germanium Oxide (BGO) imaging calorimeter is utilized to measure the particle energy with a high resolution. The nonlinear fluorescence response of BGO for large ionization energy deposition, known as the quenching effect, results in an under-estimate of the energy measurement for cosmic-ray nuclei. In this paper, various models are employed to characterize the BGO quenching factors obtained from the experimental data of DAMPE. Applying the proper quenching model in the detector simulation process, we investigate the tuned energy responses for various nuclei and compare the results based on two different simulation softwares, i.e. GEANT4 and FLUKA. The BGO quenching effect results in a decrease of the measured energy by approximately $2.5\%$ ($5.7 \%$) for carbon (iron) at $\sim$10 GeV/n and $<1\%$ above 1 TeV/n, respectively. Accordingly, the correction of the BGO quenching effect leads to an increase of the low-energy flux measurement of cosmic-ray nuclei.

hep-ex↗

arXiv2023

Multi-messenger observations support cosmic ray interactions surrounding acceleration sources

The observations of the energy spectra of cosmic-ray have revealed complicated structures. Especially, spectral hardenings in the boron-to-carbon and boron-to-oxygen ratios above $\sim 200$ GV has been revealed by AMS-02 and DAMPE experiments. One scenario to account for the hardenings of secondary-to-primary ratios is the nuclear fragmentation of freshly accelerated particles around sources. In this work, we further study this scenario based on new observations of Galactic diffuse gamma rays by LHAASO and neutrinos by IceCube. We find that the spectra of cosmic ray nuclei, the diffuse ultra-high-energy gamma rays, and the Galactic component of neutrinos can be simultaneously explained, given an average confinement and interaction time of $\sim 0.25$ Myr around sources. These multi-messenger data thus provide evidence of non-negligible grammage of Galactic cosmic rays surrounding sources besides the traditional one during the propagation.

astro-ph.HE↗

arXiv2023

Constraining ultralight dark matter using the Fermi-LAT pulsar timing array

Ultralight dark matter (ULDM) is proposed as a theoretical candidate of dark matter particles with masses of approximately $10^{-22}$ eV. The interactions between ULDM particles and standard model particles would cause variations in pulse arrival times of millisecond pulsars, which means that the pulsar timing array (PTA) can be used to indirectly detect ULDM. In this letter, we use the gamma-ray PTA composed of 29 millisecond pulsars observed by the Fermi Large Area Telescope (Fermi-LAT) to test four ULDM effects, including gravitational effects for generalized ULDM with different Spin-0/1, the fifth-force coupling effect of dark photon, and the modified gravitational effect of the Spin-2 ULDM. The gamma-ray pulsar timing is not affected by the ionized interstellar medium and suffers relatively simple noises, unlike that of the radio band. Our work is the first time that the gamma-ray PTA has been used to search for the ULDM. No significant signals of ULDM are found based on the Fermi-LAT PTA for all four kinds of ULDM models. Constraints on ULDM parameters are set with the 95% confidence level, which provides a complementary check of the nondetection of ULDM for radio PTAs and direct detection experiments.

astro-ph.HE↗

arXiv2023

Potential of Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy cosmic-Radiation Detection facility onboard China's Space Station

Precise measurements of the spectra of secondary and primary cosmic rays are crucial for understanding the origin and propagation of those energetic particles. The High Energy cosmic-Radiation Detection (HERD) facility onboard China`s Space Station, which is expected to operate in 2027, will push the direct measurements of cosmic ray fluxes precisely up to PeV energies. In this work, we investigate the potential of HERD on studying the propagation of cosmic rays using the measurements of boron, carbon, and oxygen spectra. We find that, compared with the current results, the new HERD measurements can improve the accuracy of the propagation parameters by 8\% to 40\%. The constraints on the injection spectra at high energies will also be improved.

astro-ph.HE↗

arXiv2023

Prospects for detection rate of very-high-energy γ-ray emissions from short γ-ray bursts with the HADAR experiment

The observation of short gamma ray bursts (SGRBs) in the TeV energy range plays an important role in understanding the radiation mechanism and probing new areas of physics such as Lorentz invariance violation. However, no SGRB has been observed in this energy range due to the short duration of SGRBs and the weakness of current experiments. New experiments with new technology are required to detect sub-TeV SGRBs. In this work, we observe the very high energy (VHE) $γ$-ray emissions from SGRBs and calculate the annual detection rate with the High Altitude Detection of Astronomical Radiation HADAR (HADAR) experiment. First, a set of pseudo-SGRB samples is generated and checked using the observations of Fermi-GBM, Fermi-LAT, and SWIFT measurements. The annual detection rate is calculated from these SGRB samples based on the performance of the HADAR instrument. As a result, the HADAR experiment can detect 0.5 SGRB per year if the spectral break-off of $γ$-rays caused by the internal absorption is larger than 100 GeV. For a GRB09010-like GRB in HADAR's view, it should be possible to detect approximately 2000 photons considering the internal absorption. With a time delay assumption due to the Lorentz invariance violation effects, a simulated light curve of GRB090510 has evident energy dependence. We hope that the HADAR experiment can perform the SGRB observations and test our calculations in the future.

astro-ph.HE↗

arXiv2023

Interpretations of the cosmic ray secondary-to-primary ratios measured by DAMPE

Precise measurements of the boron-to-carbon and boron-to-oxygen ratios by DAMPE show clear hardenings around $100$ GeV/n, which provide important implications on the production, propagation, and interaction of Galactic cosmic rays. In this work we investigate a number of models proposed in literature in light of the DAMPE findings. These models can roughly be classified into two classes, driven by propagation effects or by source ones. Among these models discussed, we find that the re-acceleration of cosmic rays, during their propagation, by random magnetohydrodynamic waves may not reproduce sufficient hardenings of B/C and B/O, and an additional spectral break of the diffusion coefficient is required. The other models can properly explain the hardenings of the ratios. However, depending on simplifications assumed, the models differ in their quality in reproducing the data in a wide energy range. The models with significant re-acceleration effect will under-predict low-energy antiprotons but over-predict low-energy positrons, and the models with secondary production at sources over-predict high-energy antiprotons. For all models high-energy positron excess exists.

astro-ph.HE↗

arXiv2022

Understanding the phase reversals of Galactic cosmic ray anisotropies

The energy spectra and anisotropies are very important probes of the origin of cosmic rays. Recent measurements show that complicated but very interesting structures exist, at similar energies, in both the spectra and energy-dependent anisotropies, indicating a common origin of these structures. Particularly interesting phenomenon is that there is a reversal of the phase of the dipole anisotropies, which challenges a theoretical modeling. In this work, for the first time, we identify that there might be an additional phase reversal at $\sim 100$ GeV energies of the dipole anisotropies as indicated by a few underground muon detectors and the first direct measurement by the Fermi satellite, coincident with the hundreds of GV hardenings of the spectra. We propose that these two phase reversals, together with the energy-evolution of the amplitudes and spectra, can be naturally explained with a nearby source overlapping onto the diffuse background. As a consequence, the spectra and anisotropies can be understood as the scalar and vector components of this model, and the two reversals of the phases characterize just the competition of the cosmic ray streamings between the nearby source and the background. The alignment of the cosmic ray streamings along the local large-scale magnetic field may play an important but sub-dominant role in regulating the cosmic ray propagation. More precise measurements of the anisotropy evolution at both low energies by space detectors and high energies by air shower experiments for individual species will be essential to further test this scenario.

astro-ph.HE↗

arXiv2022

An Unsupervised Machine Learning Method for Electron--Proton Discrimination of the DAMPE Experiment

Galactic cosmic rays are mostly made up of energetic nuclei, with less than $1\%$ of electrons (and positrons). Precise measurement of the electron and positron component requires a very efficient method to reject the nuclei background, mainly protons. In this work, we develop an unsupervised machine learning method to identify electrons and positrons from cosmic ray protons for the Dark Matter Particle Explorer (DAMPE) experiment. Compared with the supervised learning method used in the DAMPE experiment, this unsupervised method relies solely on real data except for the background estimation process. As a result, it could effectively reduce the uncertainties from simulations. For three energy ranges of electrons and positrons, 80--128 GeV, 350--700 GeV, and 2--5 TeV, the residual background fractions in the electron sample are found to be about (0.45 $\pm$ 0.02)$\%$, (0.52 $\pm$ 0.04)$\%$, and (10.55 $\pm$ 1.80)$\%$, and the background rejection power is about (6.21 $\pm$ 0.03) $\times$ $10^4$, (9.03 $\pm$ 0.05) $\times$ $10^4$, and (3.06 $\pm$ 0.32) $\times$ $10^4$, respectively. This method gives a higher background rejection power in all energy ranges than the traditional morphological parameterization method and reaches comparable background rejection performance compared with supervised machine learning~methods.

astro-ph.IM↗

arXiv2022

Constraining cosmological phase transitions with the Parkes Pulsar Timing Array

A cosmological first-order phase transition is expected to produce a stochastic gravitational wave background. If the phase transition temperature is on the MeV scale, the power spectrum of the induced stochastic gravitational waves peaks around nanohertz frequencies, and can thus be probed with high-precision pulsar timing observations. We search for such a stochastic gravitational wave background with the latest data set of the Parkes Pulsar Timing Array. We find no evidence for a Hellings-Downs spatial correlation as expected for a stochastic gravitational wave background. Therefore, we present constraints on first-order phase transition model parameters. Our analysis shows that pulsar timing is particularly sensitive to the low-temperature ($T \sim 1 - 100$ MeV) phase transition with a duration $(β/H_*)^{-1}\sim 10^{-2}-10^{-1}$ and therefore can be used to constrain the dark and QCD phase transitions.

astro-ph.CO↗

arXiv2022

Constraining ultralight bosonic dark matter with Keck observations of S2's orbit and kinematics

Ultralight bosonic dark matter is expected to be able to form a cloud surrounding the supermassive black hole (SMBH) in the Galactic center. With increasing precision of the observations of the stellar kinematics around the SMBH, tiny effects from such a dark matter cloud, including its gravitational perturbation and the direct coupling with the ordinary matter may be detectable. In this work, we search for possible evidence of the scalar cloud using accurate orbital measurements of the S2 star around Sgr~A*. We solve the first order Post-Newtonian equation, considering simultaneously the extended mass distribution of the scalar cloud and the frequency shift induced by the additional coupling via Higgs portal or photon portal interaction. Furthermore, we also investigate the impact of an astrophysical power-law component from the gas and stellar remnants. We find that the astrometric and spectroscopic data of the S2 star are well consistent with the scenario of a point-like mass of Sgr~A*. We thus derive upper limits of the coupling of the new interaction and the extended mass, with and without the contribution from the astrophysical component. The limits of the Higgs/photon coupling and the extended mass of the scalar cloud are the most stringent ones for the scalar mass window between $3.2\times 10^{-19}$~eV and $1.6\times 10^{-18}$~eV.

astro-ph.HE↗

arXiv2022

Explaining the GeV antiproton/$γ-$ray excesses and W-boson mass anomaly in an inert two Higgs doublet model

For the newly discovered $W$-boson mass anomaly, one of the simplest dark matter (DM) models that can account for the anomaly without violating other astrophysical/experimental constraints is the inert two Higgs doublet model, in which the DM mass ($m_{S}$) is found to be within $\sim 54-74$ GeV. In this model, the annihilation of DM via $SS\to b\bar{b}$ and $SS\to WW^{*}$ would produce antiprotons and gamma rays, and may account for the excesses identified previously in both particles. Motivated by this, we re-analyze the AMS-02 antiproton and Fermi-LAT Galactic center gamma-ray data. For the antiproton analysis, the novel treatment is the inclusion of the charge-sign-dependent three-dimensional solar modulation model as constrained by the time-dependent proton data. We find that the excess of antiprotons is more distinct than previous results based on the force-field solar modulation model. The interpretation of this excess as the annihilation of $SS\to WW^{*}$ ($SS\to b\bar{b}$) requires a DM mass of $\sim 40-80$ ($40-60$) GeV and a velocity-averaged cross section of $O(10^{-26})~{\rm cm^3~s^{-1}}$. As for the $γ$-ray data analysis, besides adopting the widely-used spatial template fitting, we employ an orthogonal approach with a data-driven spectral template analysis. The fitting to the GeV $γ$-ray excess yields DM model parameters overlapped with those to fit the antiproton excess via the $WW^{*}$ channel. The consistency of the DM particle properties required to account for the $W$-boson mass anomaly, the GeV antiproton excess, and the GeV $γ$-ray excess suggest a common origin of them.

astro-ph.HE↗

arXiv2022

Birefringence Tomography for Axion Cloud

An axion cloud surrounding a supermassive black hole can be naturally produced through the superradiance process. Its existence can be examined by the axion induced birefringence effect. It predicts an oscillation of the electric vector position angle of linearly polarized radiations. Stringent constraints of the existence of the axion in a particular mass window has been obtained based on the recent Event Horizon Telescope measurement on M87$^\star$. The future Very-Long-Baseline Interferometry (VLBI) observations will be able to measure the vicinity of many supermassive black holes, thus it opens the possibility to search for the existence of axions in a wide mass regime. In this paper, we study how different black hole properties and accretion flows influence the signatures of the axion induced birefringence. We include the impacts of black hole inclination angles, spins, magnetic fields, plasma velocity distributions, the thickness of the accretion flows. We pay special attention to characterize the washout effects induced by the finite thickness of the accretion flows and the lensed photons. Based on this study, we give prospects on how to optimize the axion search using future VLBI observations, such as the next-generation Event Horizon Telescope, to further increase the sensitivity.

hep-ph↗