Gamma-ray Research Articles

Effective rare-earth dielectric addition and gamma ray irradiation for achieving highly efficient PDMS triboelectric nanogenerator

This research aims to develop the flexible triboelectric nanogenerator (TENG) using PDMS polymer as the main tribo-material and composite with dielectric rare earth oxide, lanthanum chromite compound; LaCrO3, to enhance generated charge density, before add-on its higher electrical output with gamma ray irradiation. Upon study the effect of different amounts of the loaded LaCrO3 and various doses of gamma ray, the optimum condition can be obtained. The PDMS/LaCrO3 at 5 wt% can reach open-circuit voltage (VOC) and shot-circuit current (ISC) at 89 V and 448 μA. The impressive results of output further appear by additional irradiated gamma radiation. At 150 kGy dose of Irradiated gamma ray, VOC and ISC can jump to 161 V and 963 μA. These output signals, especially ISC, can be ∼34 times higher than that of the pristine PDMS. Scientific discussion regarding characterization, operating mechanism, dielectric properties and electrical output is provided. The practical application of being a small power source is also developed. Therefore, this research can show another useful application of gamma ray in the field of materials design for energy harvesting devices. The knowledge provided in this research can also serve as potential guidance in the field of specific TENG utilization.

Multiple Emission Regions in Jets of the Low-Luminosity Active Galactic Nucleus in NGC 4278

The Large High Altitude Air Shower Observatory (LHAASO) has detected very-high-energy gamma rays from the low-ionization nuclear emission-line region galaxy NGC 4278, which has a low-luminosity active galactic nucleus (LLAGN) and symmetric, mildly relativistic S-shaped twin jets detected by radio observations. Few LLAGNs have been detected in gamma rays due to their faintness. Earlier, several radio-emitting components were detected in the jets of NGC 4278. We model their radio emission with synchrotron emission of ultra-relativistic electrons to estimate the strength of the magnetic field inside these components within a time-dependent framework after including the ages of the different components. We show that the synchrotron and synchrotron self-Compton emission by these components cannot explain the Swift X-ray data and the LHAASO gamma-ray data from NGC 4278. We suggest that a separate component in one of the jets is responsible for the high-energy emission, whose age, size, magnetic field, and the spectrum of the ultra-relativistic electrons inside it have been estimated after fitting the multiwavelength data of NGC 4278 with the sum of the spectral energy distributions from the radio components and the high-energy component. We note that the radio components of NGC 4278 are larger than the high-energy component, which has also been observed in several high-luminosity active galactic nuclei.

Applicability of ensemble learning in total organic carbon and porosity evaluation of shales

Accurate evaluation of total organic carbon (TOC) content and porosity is of paramount significance for assessment and target interval selection for shale reservoirs. This study takes shales from the western Chongqing area as an exemplary case to delve into the applicability and reliability of ensemble learning in evaluating TOC content and porosity. The results indicate that although both Light Gradient Boosting Machine (LightGBM) and Random Forest (RF) algorithms are suitable for evaluating TOC content and porosity in shales, LightGBM algorithm is preferred due to its comprehensive advantages, including higher accuracy, stronger generalization capability, and faster operating speed. For TOC content evaluation, the four most important logging parameters identified by LightGBM and RF are consistent, but exhibit different orders: DEN (compensated density) > GR (gamma ray) > U (uranium) > CNL (compensated neutron) and DEN > U > GR > CNL, respectively. For porosity evaluation, LightGBM and RF identify the same type and order of the three most important logging parameters: AC (acoustic transit time) > DEN > U. This similarity may be attributed to the fact that both algorithms utilize Classification and Regression Tree (CART) as base learners. The dependence plots between SHAP (SHapley Additive exPlanations) values and logging parameters reveal that the role of each logging parameter in the evaluation model is segmented, rather than exhibiting a continuous linear contribution. In conclusion, given the exceptional performance of ensemble learning algorithms, they, especially LightGBM algorithm, are highly recommended for shale evaluation.

Modeling Multiband SEDs and Light Curves of BL Lacertae Using a Time-dependent Shock-in-jet Model

The origin of fast flux variability in blazars is a long-standing problem, with many theoretical models proposed to explain it. In this study, we focus on BL Lacertae to model its spectral energy distribution (SED) and broadband light curves using a diffusive shock acceleration process involving multiple mildly relativistic shocks, coupled with a time-dependent radiation transfer code. BL Lacertae was the target of a comprehensive multiwavelength monitoring campaign in early 2021 July. We present a detailed investigation of the source’s broadband spectral and light-curve features using simultaneous observations at optical–UV frequencies with the Swift Ultraviolet/Optical Telescope, in X-rays with the Swift X-Ray Telescope and AstroSat-SXT/LAXPC, and in gamma rays with Fermi-LAT, covering the period from 2021 July to August (MJD 59400–59450). A fractional variability analysis shows that the source is most variable in gamma rays, followed by X-rays, UV, and optical. This allowed us to determine the fastest variability time in gamma rays to be on the order of a few hours. The AstroSat-SXT and LAXPC light curves indicate X-ray variability on the order of a few kiloseconds. Modeling simultaneously the SEDs of low- and high-flux states of the source and the multiband light curves provided insights into the particle acceleration mechanisms at play. This is the first instance of a physical model that accurately captures the multiband temporal variability of BL Lacertae, including the hour-scale fluctuations observed during the flare.

Prospects for a survey of the galactic plane with the Cherenkov Telescope Array

Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios.Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.

Nonthermal Signatures of Radiative Supernova Remnants

The end of supernova remnant (SNR) evolution is characterized by a so-called “radiative” stage, in which efficient cooling of the hot bubble inside the forward shock slows expansion, leading to eventual shock breakup. Understanding SNR evolution at this stage is vital for predicting feedback in galaxies, since SNRs are expected to deposit their energy and momentum into the interstellar medium at the ends of their lives. A key prediction of SNR evolutionary models is the formation at the onset of the radiative stage of a cold, dense shell behind the forward shock. However, searches for these shells via their neutral hydrogen emission have had limited success. We instead introduce an independent observational signal of shell formation arising from the interaction between nonthermal particles accelerated by the SNR forward shock (cosmic rays) and the dense shell. Using a semi-analytic model of particle acceleration based on state-of-the-art simulations coupled with a high-resolution hydrodynamic model of SNR evolution, we predict the nonthermal emission that arises from this interaction. We demonstrate that the onset of the radiative stage leads to nonthermal signatures from radio to gamma rays, including radio and gamma-ray brightening by nearly 2 orders of magnitude. Such a signature may be detectable with current instruments, and will be resolvable with the next generation of gamma-ray telescopes (namely, the Cherenkov Telescope Array).

Sustainable wood composite production using cotton waste and exopolysaccharides as green binders

Burning agricultural waste is a common practice among farmers in many countries, leading to global warming and climate change. Upcycling abundant agricultural waste will prevent incineration-generated hazards and provide sustainable and eco-friendly wood. An alternative wood composite was prepared using Aspergillus niger mycelium and exopolysaccharides (EPS) as a green binder. Autoclaving and gamma irradiation were both tested as wood pre-treatment to enhance binding. The mixture was incubated at 30 °C for 1 week. The results showed that wet pre-treatment using autoclaving resulted in improved wood binding compared to dry gamma irradiation treatment. The results show that the composite with the lowest water absorption was autoclaved before inoculation with 25 % EPS-induced Aspergillus niger, its tensile strength was 2.01 MPa and Modulus of elasticity of 1240.42 MPa and water resistance duration of 72 h. The biodegradation rate was 21.5 % for linseed oil-coated composite compared to 15.63 % for non-coated wood after 6 weeks. The samples demonstrated thermal conductivity as low as 0.06025 W/mK and linear Ohmic behavior within the investigated voltage range, rendering it a competitive insulating material. In conclusion, autoclaving and inoculum size play a key role in binding cotton wood waste. The key results render the optimized composite suitable for industrial applications due to its affordability, green manufacturing process, and potential for large-scale production.

Synergistic effects of gamma irradiation and butylated hydroxyanisole on the sensory, physicochemical, and microbiological quality of beef

The objective of this study was to investigate the impact of gamma irradiation, in combination with the synthetic antioxidant butylated hydroxyanisole (BHA), on the safety and quality characteristics of refrigerated beef. The samples were divided into four treatment groups, which were subjected to marinating with 0.01% BHA and gamma irradiation at different dosages. The treatment groups were labeled as follows: T0 (control, non-irradiated), T1 (3 kGy), T2 (5 kGy), and T3 (7 kGy). The specimens in each group were stored under refrigerated conditions at a temperature of 4°C for intervals of 0, 5, 10, or 15 days. Data analyses were conducted using a Completely Randomized Design (CRD) with a 4 × 4 factorial experiment. The experiment consisted of two factors, each with four treatments, and was reproduced three times with a 4-day gap. The instrumental color value CIE: lightness (L*), redness (a*) and yellowness (b*) and physicochemical properties, including pH, drip loss, cook loss, extract release volume, and water holding capacity, were analyzed. The proximate components, including dry matter (DM), crude protein (CP), ether extract (EE), ash, and moisture, were found to have a significant effect (p < 0.01)(p < 0.01) among treatment groups, time intervals, and their interaction. Free fatty acids (FFA), peroxide value (POV), and thiobarbituric acid reactive substances (TBARS) significantly increased (p < 0.01)(p < 0.01)(p < 0.01) among treatments and over the course of storage. Following the irradiation with BHA, there was a notable reduction in microbial populations and a delay in lipid oxidation. The sensory characteristics stipulated that both the control samples and the samples treated with BHA were more favored than the irradiated samples as the storage time progressed. Although treatment may cause some changes in the sensory characteristics of the meat, the samples were deemed suitable for refrigerated storage for a maximum duration of 10 days. In summary, the utilization of irradiation in conjunction with BHA presents a possible avenue for enhancing the quality and safety of refrigerated beef storage, hence offering promising applications within the meat sector.

Genetic variability increase by gamma irradiation of soybean seeds

The increase of genetic variability by the appearance of new genes of agronomic interest may be favored by the use of gamma radiation. The objective of this study was to evaluate different doses of gamma irradiation on dry seeds of VX04-5692 soybean line, aiming to increase the genetic variability and, with this, the identification of possible mutant plants. The doses of 0, 50, 150 and 250 Gy of gamma radiation were applied from a60Co source. The newly irradiated seeds were sown in the field, giving rise to the M1 cycle. Selected plants originated the M2 cycle. The number of seedlings was counted on the 21st day after sowing. Ten plants of each row were identified and evaluated for the various agronomic characteristics and for chemical composition. The data were submitted to analysis of variance. The F test was applied and the results were presented by boxplots and biplot (canonical variables). There was effect of gamma radiation doses at plant height at full bloom and maturity, number of nodes, pods with one seed and seeds per pod. The use of gamma radiation increases the variability in soybean, with consequent increase in the probabilities of identification of new mutants and gains in the chemical composition, useful for breeding programs that aim at better agronomic performance and gains in oil and protein contents. More satisfactory results in the generation of variability are obtained by the application of gamma radiation on soybean dry seeds between 50 and 150 Gy.

Modification of activated carbon through chemical-physical activation method with KOH and 60Co gamma irradiation from banana leaf waste

Abstract Until now waste is still a problem in many big cities in Indonesia. In addition, the amount of waste increases as the population increases. Banana leaf waste is no exception, which is included in other types of waste, which accounts for 6.33% of the total waste in Indonesia in 2022. Utilization of banana leaf waste as a raw material for activated carbon production can also be an alternative to reducing the amount of wasted banana leaf waste because they contain various kinds of organic compounds. Activated carbon is widely used as an adsorbent in various sectors, especially in the industrial sector. Production of activated carbon must go through an activation process to enlarge the surface pores either chemically or physically, or even both. This study aims to compare the results of activated carbon surface area and functional groups using the chemical-physical activation method from banana leaf biomass raw materials with KOH and gamma irradiation at various doses. The research method used is an experimental method consisting of 4 stages: dehydration, carbonization, activation, and characterization. The research was started by dehydrating the leaves and continued with the carbonization stage at 350°C for 30 minutes. Carbon was divided into four samples that consisted of 1 blank and 3 test materials that activated with 30% (w/v) KOH solution for 24 hours and gamma-irradiated with a dose of 10, 30, and 50 kGy. Results were characterized using FTIR and BET. The effect of gamma 60Co irradiation on the activated carbon material from banana leaf waste can increase the peak transmittance value of the activated carbon functional group due to the formation and reaction of free radicals on its surface. Increase in the surface area (from 6.504 to 24.04 m2/g) is also associated with an increase in the absorbed dose due to the formation of more free radicals. However, the surface area obtained is not as expected due to the possibility of pore blockage and excessive activation time, which causes the surface area of the material to be small.

Gamma Radiolysis of n‐Dodecane: Physicochemical Properties and Metal Retention Behavior

AbstractThe gamma radiolytic degradation behavior of n‐dodecane (n‐DD) was investigated under conditions both with and without the presence of nitric acid. The physicochemical property alterations due to radiolysis were quantified and compared against an unirradiated system. Compositional changes in n‐DD post radiolysis was measured, and the degraded n‐DD was characterized using Fourier‐transform infrared (FT‐IR) spectroscopy, gas chromatography (GC), and gas chromatography–mass spectrometry (GC–MS) analysis. The presence of nitric acid was observed to accelerate the radiolytic degradation of n‐DD. The extent of diluent degradation caused by gamma irradiation was assessed through the retention behavior of uranium [U(VI)], plutonium [Pu(IV)], and zirconium [Zr(IV)] in 1.1 M tri‐n‐butyl phosphate (TBP) in irradiated diluent. Furthermore, the effectiveness of hydrazine carbonate (HC) as a solvent wash reagent for the removal of diluent degradation products was evaluated.

Tailoring optical and electrical properties of PVP-I2 complexes through gamma irradiation-induced structural defect Engineering for optoelectronic applications

This study investigates the complexation of iodine with polyvinylpyrrolidone (PVP) subjected to gamma irradiation at doses of 0, 10, 20, and 30 kGy. The complex formation involves I2 acting as a Lewis acid with electron-rich PVP as a Lewis base through a charge transfer mechanism. UV–visible spectroscopy revealed a red shift of the absorption peak at 337 nm for irradiated PVP-I2 samples, indicating stronger interactions between the triiodide ion (I3¯) and irradiated PVP. FTIR analysis confirmed the formation of new C≡N moieties arising from PVP-I2 complexation. The FT-Raman analysis revealed a new C≡N peak at 2360 cm−1 in irradiated PVP-I2 samples, with increasing intensity correlating to higher irradiation doses, indicating enhanced electron delocalization due to complex formation. XRD analysis showed that PVP-I2 samples irradiated at 0 and 10 kGy exhibited higher crystallinity than those irradiated at 20 and 30 kGy, suggesting that high-dose irradiation causes PVP radiolysis and ring opening. Dielectric measurements demonstrated enhanced polarizability and ionic conductivity of irradiated PVP-I2 films, related to structural disorder promoting charge dissociation and ion mobility. The direct bandgap decreased from 2.75 eV for unirradiated samples to 2.55 eV for samples irradiated at 30 kGy, indicating the creation of new optically active defect states. Urbach energy increased from 0.85 eV to 1.55 eV with increasing irradiation dose, confirming increased disorder in the PVP structure. These findings reveal that gamma irradiation significantly alters the optical and electrical properties of PVP-I2 films by creating defects and disrupting structure, offering new insights for tailoring these materials for optoelectronic applications.

Development of a thermal diagnostic system for the SPARC tokamak.

The SPARC tokamak will have scrape-off layer parallel heat fluxes on the order of GW/m2. Managing power exhaust of this magnitude will be mandatory for a reactor-scale device. To enable this mission, a thermal diagnostic suite will be deployed to measure the in-vessel structural temperatures to ensure they do not exceed their design limits and to determine the spatial distribution and magnitude of energy deposited onto the first wall. Thermocouples and fiber Bragg gratings have been selected for their environmental compatibility and proven useful on other fusion devices. High-density thermocouple arrays in the divertor will have two spring-loaded thermocouples per divertor target tile, which are being used as calorimeters, and will look to resolve the temperature distribution within the tile due to a swept or static strike point. All systems will need to survive the vacuum vessel bake, set at a minimum plasma facing surface temperature of 350 °C, which presents a particularly challenging environment for the fiber-based subsystem. Along with this temperature design requirement, all the materials in the primary vacuum need to be ultra-high vacuum compatible, able to handle the expected neutron and gamma radiation, as well as tritium exposure, all of which restrict material options. Finally, due to the expected activated environment in SPARC, there will be little chance to replace defective sensors, so system resilience is ensured through toroidal redundancy, probe material selection, and mitigating the impact of common-mode failures. Initial testing of sensors show that intershot structural measurements are sufficiently captured with the raw output, but intrashot measurements of the plasma facing material requires model-based interpretive tools.

Study on Characteristics of Epoxy Resin-Based Plastic Scintillators for Detectors with Simulation Using Monte Carlo Code

Abstract To determine the presence of radioactive materials emitting gamma rays entering or exiting nuclear facilities, ports, airports, international borders, or other strategic locations, radiation portal monitors (RPMs) capable of detecting such gamma radiation need to be installed in these places. National Research and Innovation Agency of Indonesia (BRIN) is currently developing RPMs with detector components made of plastic scintillator based on epoxy resin and augmented with aromatic fluorescent materials to produce visible light, which is the working range of the photomultiplier tube (PMT) or silicon photomultiplier (SiPM). This research aims to study the characteristics of the gamma photon radiation energy spectrum from Co-60, Cs-137, and Ir-192 sources in an epoxy resin plastic scintillator and study the absorbed dose of the scintillator to gamma photon radiation energy from Co-60, Cs-137, and Ir-192 sources as a function of source distance and incidence angle of gamma rays with simulations using the MCNPX code. The scintillator is modeled in the form of a cylinder with a diameter of 5 cm and a height of 5 cm. To simulate the gamma photon radiation energy spectrum in the scintillator, the F4 tally was used and to simulate the scintillator absorbed dose, the F6 tally was used. This simulation used gamma sources of Co-60, Cs-137, and Ir-192 of 1 mCi each. These characteristics of the epoxy resin plastic scintillator have been successfully simulated. Data on the characteristics of epoxy resin plastic scintillators is important to know and study as supporting data in making plastic detectors as part of the manufacture and development of RPM.

Optimizing the radiation synthesis and swelling of agar-based acrylate superabsorbent hydrogel for irrigation water conservation

This study reports the synthesis of novel agar/poly methacrylic acid/poly acrylic acid (AG/PMAc/PAc) superabsorbent hydrogels via gamma radiation and their subsequent urea modification to enhance swelling and water retention for agricultural applications. The superabsorbent hydrogels were prepared by irradiating aqueous mixtures of varying agar concentrations with methacrylic acid/acrylic acid (MAc/Ac) monomers, followed by urea treatment at different cycles and concentrations. The morphological characteristics and chemical structures were confirmed by SEM and FTIR, respectively. The maximum swelling occurred at 6 % agar and 1 % urea modification. Remarkably, the 1 % urea-modified hydrogel displayed a 41.1 % swelling increase and 236.4 % enhancement after the second modification cycle compared to unmodified samples. Water retention studies showed the modified hydrogel retained 53.2 % moisture after 14 days versus the complete drying of unmodified hydrogels. Soil application studies demonstrated the modified hydrogel increased moisture content by 177.3 % after 20 days, promoting better growth with 30 % more leaves and 38.9 % higher stem length in Vicia faba plants versus controls. This novel radiation-synthesized, urea-modified hydrogel with exceptional swelling and moisture retention capabilities shows promising potential for sustainable agricultural irrigation and crop productivity enhancement under water-deficit conditions.

Polyvinyl alcohol dyed with methyl red as a radiochromic film dosimeter for gamma radiation

Abstract A Radiochromic film dosimeter for gamma radiation was prepared from polyvinyl alcohol (PVA) and methyl red (MR) by condensation polymerization. To confirm the reaction, the obtained PVA-MR film was characterized by Fourier-transform infrared spectroscopy (FTIR) and compared to PVA film. The result shows the appearance of new vibrational stretching at ~1700 cm−1, related to carbonyl groups, indicating that the reaction between PVA and MR has been successfully done. The effect of radiation on the color change characteristic of PVA-MR film and its possibility to be used as a radiochromic film dosimeter were investigated using ultraviolet (UV)-Vis spectrophotometry. The absorption spectrum of PVA-MR can be seen in the visible region at ~420 nm, which is characteristic of red, and the film undergoes decolorization gradually from red to transparent when exposed to gamma radiation up to 100 kGy. Moreover, the response of these dosimeters at different times after irradiation was tested and the energy band gap, Eg, was also calculated.

Effects of electron beam and atomic oxygen irradiation on hypervelocity - Impact tested / polyimide coated carbon fiber-reinforced plates

In a low-Earth orbit, space debris orbit at approximately the first cosmic velocity. When space debris strike a spacecraft, ejecta (fragments) from the spacecraft are widely scattered. The reduction in the number of ejecta (fragments caused by impact) must also be considered when selecting spacecraft materials. The authors’ group has previously examined the size of ejecta (fragments) and reduction in the number of ejecta. In general, the mechanical properties of polymer materials and CFRP plates may be damaged by space environments, such as radiation (gamma rays and electron beams (EBs)), atomic oxygen (AO), ultraviolet rays, temperature, and thermal cycling. The authors suggested an anti-AO coating/polyimide CFRP as a material resistant to space environments. The effects of EB and AO irradiation on the fracture behavior and ejecta of anti-AO coating/polyimide CFRP were examined for hypervelocity impacts. The results of static three-point flexural tests were compared with the fracture behavior and ejecta. A two-stage light-gas gun was used for the impact tests. Spherical projectiles formed of aluminum alloy 2017-T4 with a diameter of 1.6 mm were used. Photographs of the ejecta scattered in front of each polyimide CFRP plate were captured from the side using a high-speed video camera. The number and weight of the ejecta on the front side and perforation holes were examined.

Influence of gamma-irradiation on the physical properties of epoxy/polyaniline composites and application as gamma dosimeter

Abstract The epoxy/pani samples doped with a specified weight ratio of polyaniline pani ware prepare by casting method. Using different doses of gamma rays (0, 2, and 4 kGy) were used to irradiated the prepared samples. Irradiated and non-irradiated samples were imaged using a FE-scanning electron microscope and were found to have regular morphology, and irradiation had obvious effect on this morphology at 4 kGy. When studying the crystal structure of the samples, it was found the samples have a polycrystalline structure, and this structure tends to improve after irradiation, this was verified using X-ray diffraction. Likewise, D.C electrical conductivity increased with increasing gamma radiation doses. Also study the effect of irradiation with gamma rays on optical properties and demonstrate the clear effect of these rays on optical properties. It was also found that the optical energy gap with (indirect allowed transition) was decreases after the irradiation process. Together, these results indicate the possibility of using these samples in the manufacture of gamma dosimeters.

Origin of the Very High Energy Gamma Rays in the Low-luminosity Active Galactic Nucleus NGC 4278

NGC 4278, a low-luminosity active galactic nucleus, is generally classified as a low-ionization nuclear emission-line region (LINER). Recently, it has been reported to be associated with a very high energy γ-ray source 1LHAASO J1219+2915 in the first Large High Altitude Air Shower Observatory source catalog. However, no associated counterpart has been detected by analyzing the data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. By analyzing its X-ray observation data from Swift-XRT, we find that NGC 4278 is in a high-flux state on MJD 59546, with the X-ray flux more than one order of magnitude higher than that observed ∼11.7 yr earlier by Chandra. Interestingly, this Swift-XRT observation was conducted during the active phase of the γ-ray source 1LHAASO J1219+2915. We propose that the detection of very high energy γ-rays from NGC 4278 may be attributed to the presence of an active nucleus in its center. To reproduce the spectral energy distribution (SED) of NGC 4278, we employ a one-zone leptonic model, typically used for fitting broadband SEDs of BL Lacs, and find that a smaller magnetic field strength is required than that of typical TeV BL Lacs. Furthermore, NGC 4278 exhibits significantly lower luminosity in both radio and TeV bands when compared with typical TeV BL Lacs. In the radio luminosity versus Eddington ratio plane, NGC 4278 shows greater similarity to Seyfert galaxies and LINERs than to BL Lacs; however, it still roughly follows the extension toward lower luminosity seen in BL Lacs.

Gamma-ray irradiation-induced effects on Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glass: Structural, Optical, Luminescence, and Radiation Shielding Properties

In the present study, we report the gamma (γ) ray irradiation-induced structural, optical, luminescence and radiation shielding properties of Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glasses prepared by melt-quenching technique. It was evidence of the slight reductions in density and refractive index while maintaining stable optical properties upon the γ irradiation. Additionally, increased molar volume and polarizability indicated a less compact network. Raman spectroscopy shows broadened peaks and intensity reductions at key vibrational modes. The UV-Vis-NIR absorption spectra reveal the shift in the absorption edge and reduction in the intensities of Er³⁺ absorption bands (around 450, 520, 550, and 650 nm) with higher radiation doses, indicating radiation-induced damage. It was found that the band gap values decreased from 2.58 eV to 1.30 eV for un-irradiated glass to 90 kGy irradiated glass, and Urbach energy was found to increase from 0.18 to 1 eV respectively, indicating structural disorder and localized states within the band gap. PL emission spectra demonstrated intensity changes and peak shifts with γ radiation dose while maintaining a dominant green emission from 4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions, supported by the CIE diagram analysis. The NIR emission spectra also displayed a peak at 1530 nm with decreasing intensity, indicating defect-induced non-radiative recombination centres. Luminescence lifetime decay profiles indicated reduced lifetimes at higher γ doses, suggesting introduced non-radiative decay pathways. Furthermore, Phy-X software analysis highlighted effective γ-ray shielding influenced by chemical composition and photon flux, with MAC sharply decreasing to 1.8 cm2/g at 0.1 MeV and stabilizing, while LAC showed reduced attenuation efficiency at higher energies. HVL and TVL increased with energy, stabilizing around 4-5 cm and 15-16 cm, respectively, necessitating thicker materials for effective shielding at higher photon energies. MFP rapidly increased to 6-7 cm at 2 MeV, stabilizing at higher energies, while Zeff decreased sharply before stabilizing around 1 MeV. The EBF and EABF trends exhibited higher values at low energies, stabilizing at higher energies, indicating effective photon interaction and resonance effects.