A new perspective on the diffuse gamma-ray emission excess

The Large High-Altitude Air Shower Observatory(LHAASO)recently published measurements of diffuse Galactic gamma-ray emission(DGE)in the 10−1000 TeV energy range.The measured DGE flux is significantly higher than the expectation from hadronic interactions between cosmic rays(CRs)and the interstellar medium.This excess has been proposed to originate from unknown extended sources produced by electron radiation,such as pulsar wind nebulae or pulsar halos(PWNe/halos).In this paper,we propose a new perspective to explain the DGE excess observed by LHAASO.The masking regions used in the LHAASO DGE measurement may not fully encompass the extended signals of PWNe/halos.By employing a two-zone diffusion model for electrons around pulsars,we find that the DGE excess in most regions of the Galactic plane can be well explained by the signal leakage model under certain parameters.Our results indicate that this signal leakage from known sources and contributions from unresolved sources should be considered as complementary in explaining the DGE excess.

NITROGEN DETERMINATION IN THE SURFACE OF NITRIDED STEEL USING PROTON INDUCED GAMMA-RAY EMISSION ANALYSIS

Ⅰ. INTRODUCTIONIt has been established for some time that introduction of nitrogen in the surface and near surface regions of metal alloys can make important modifications in surface properties of the alloys such as hardness, wear and friction, corrosion resistance and fatigue time. Proton induced gamma-ray emission (PIGE) analysis provides a useful method for direct determination of nitrogen concentration in the surface of nitrided samples and also for its quality test and the investigation of new nitriding technology.The aims of the present work are to study the optimum conditions of

^(134)Cs衰变γ射线发射率的测量及一个简单的符合格加修正方法

借助一套高性能的多道计算机γ谱仪系统，精确测量了￣（１３４）衰变γ射线的绝对发射率和相对发射率。并且使用了一个简单的符合相加修正方法，对￣（１３４）Ｇｓ衰变的两条主要的级联γ射线的符合相加进行了修正，获得了较好的结果。

One-Dimensional Electric Field Structure of an Outer Gap Accelerator

We re-study the one-dimensional electric field structure of an outer gap accelerator by considering the physical limit of trans-field height. Inside the outer gap, the charge depletion creates a large electric field along the magnetic field lines. Electrons and/or positrons are accelerated to ultra-relativistic energies by this longitudinal electric field, and then radiate γ-ray photons by curvature radiation. The collision of these γ-rays and ambient x-ray photons further produce radiating particles, resulting in a stationary gap. We solve the structure of this longitudinal electric field together with the distributions of electrons and positrons and γ-ray photons for an aligned rotator. Our results indicate that the outer gap can extend to the light cylinder using reasonable parameters.

AGN Singularities and Jets Modelled with the Superstar Scenario

In this paper we present solutions with the superstar scenario for the problems of singularity and the relativistic jet in AGN (Active Galactic Nuclei) based on supermassive black hole with singularity. The five-zone structure of superstar from inside to outside consists of the Singularity-Free Superstar Core (SC), the short-range repulsive super force field (SFF) near the event horizon, the superstar lepton sphere (SLS) containing infalling leptons (electron-positron pairs), the superstar ergosphere (SE), and the superstar accretion disk (SAD). As in the Meissner effect in superconductor, the short-range SFF repulses leptons in the SLS preventing singularity, while infalling leptons from the SAD and the SE continue to enter the SLS through the strong gravity of the SC. When the density at the bottom of the SLS reaches the critical density, leptons fall into the SC with the corresponding size increase of the SC to prevent singularity. Without further infalling leptons, the short-range repulsive force from the SFF disintegrates the SLS into the SLS plasma fragments (electron-positron pair plasma), detaching from the SC. Some SLS plasma fragments in the SAD generate the broad relativistic SAD jet, and some SLS plasma fragments in the SE generate the coincident narrow relativistic SE jet. In this two-jet model (the origin of the spine-sheath jet structure), protected by the SAD jet, the fast and narrow SE jet inside the slow and broad SAD jet generates the VHE (very high energy ≥ 100 GeV) Synchrotron Self Compton (SSC) gamma-ray emission without the attenuation by the photons in the BLR (broad line region) of flat spectrum radio quasar (FSRQ). In conclusion, AGN based on supermassive superstar provide the solutions for singularity, VHE gamma-ray emissions in FSRQs and FR1 type radio galaxies, AGN jet structure, and AGN jet type.

Recent observations and research progresses of terrestrial gamma-ray flashes during thunderstorms

Terrestrial gamma-ray flashes(TGFs)are high-energy emissions in thunderstorms that were discovered first by satellite-based and then by ground-based gamma-ray detectors with photon energy up to tens of Me V.TGFs are a natural highenergy phenomenon associated with lightning discharges that frequently occur during thunderstorms.However,their production mechanisms and associated processes are still unclear.TGF studies have already been a research spotlight in the atmospheric electricity and high-energy atmosphere research areas.In this paper,we review recent research progresses on TGF studies in the past decade,including TGF detection,the relationship between TGFs and lightning processes,and thunderstorm activities.Several unsolved important scientific questions are discussed.Results suggest that upward TGFs observed by satellite-based detectors are closely connected with the development of in-cloud upward negative leaders.They are usually generated in milliseconds of the initiation of upward negative leaders and may produce a kind of distinct radio emissions because of the generation and propagation of huge amounts of high-energy electrons.By contrast,its counterpart,i.e.,downward TGFs observed by ground-based gamma-ray detectors,is associated with different types of lightning processes,such as downward negative or upward positive leaders,the initial continuing current stage of rocket-triggered lightning flashes return stroke processes.Because of limited observations,how these downward TGFs are generated is still unclear.Benefiting from the development of state-of-the-art instruments with high temporal and spatial resolutions,new insights into the processes and mechanisms of TGFs will be achieved with coordinated observations from satellite-based and ground-based measurements.

The gamma-ray spectral index changes for blazars

Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.

On the detectability of Galactic dark matter annihilation into monochromatic gamma-rays

Monochromatic y-rays are thought to be the smoking gun signal for identifying dark matter annihilation. However, the flux of monochromatic y-rays is usually suppressed by virtual quantum effects since dark matter should be neutral and does not couple with y-rays directly. In this work, we study the detection strategy of the monochromatic y-rays in a future space-based detector. The flux of monochromatic y-rays between 50 GeV and several TeV is calculated by assuming the supersymmetric neutralino as a typical dark matter candidate. The detection both by focusing on the Galactic center and in a scan mode that detects y-rays from the whole Galactic halo are compared. The detector performance for the purpose of monochromatic y-ray detection, with different energy and angular resolution, field of view, and background rejection efficiencies, is carefully studied with both analytical and fast Monte-Carlo methods.

Some statistical correlation analyses for Fermi/LAT Blazars

A sample including 664 blazars （301 Flat Spectrum Radio Quasars and 363 BL Lacs） with ）γ-ray data in both 1FGL and 2FGL catalogues were selected. The average values of both y-photon average energy and the photon spectral index for FSRQs, LBLs, IBLs and HBLs, follow the blazars sequence, FSRQs → LBLs →IBLs → HBLs. The slopes of correlation between photon spectral index and ）,-ray luminosity for 4 the sub-classes of blazars also follow the blazars sequence. Also, there was close an- ti-correlations between the difference of two ）,-ray photon spectral indices and the logarithm of the ratio of two y-ray luminosities from 2FGL and 1FGL catalogs. It implies that the spectrum becomes flat when the source becomes brighter in high energetic γ-ray band. Lastly, the Kolmogolov-Smirnov test （KS test） of the average γ-photon energy showed that HBLs differs from LBLs and FSRQs, while there was no clear difference between LBLs and FSRQs, which implied that the γ-ray emissions in LBLs and FSRQs may be a result of the same emission mechanism.