High-energy Emission Research Articles

Serious game for radiotherapy training

BackgroundCancer patients are often treated with radiation, therefore increasing their exposure to high energy emissions. In such cases, medical errors may be threatening or fatal, inducing the need to innovate new methods for maximum reduction of irreversible events. Training is an efficient and methodical tool to subject professionals to the real world and heavily educate them on how to perform with minimal errors. An evolving technique for this is Serious Gaming that can fulfill this purpose, especially with the rise of COVID-19 and the shift to the online world, by realistic and visual simulations built to present engaging scenarios. This paper presents the first Serious Game for Lung Cancer Radiotherapy training that embodies Biomedical Engineering principles and clinical experience to create a realistic and precise platform for coherent training.MethodsTo develop the game, thorough 3D modeling, animation, and gaming fundamentals were utilized to represent the whole clinical process of treatment, along with the scores and progress of every player. The model’s goal is to output coherency and organization for students’ ease of use and progress tracking, and to provide a beneficial educational experience supplementary to the users’ training. It aims to also expand their knowledge and use of skills in critical cases where they must perform crucial decision-making and procedures on patients of different cases.ResultsAt the end of this research, one of the accomplished goals consists of building a realistic model of the different equipment and tools accompanied with the radiotherapy process received by the patient on Maya 2018, including the true beam table, gantry, X-ray tube, CT Scanner, and so on. The serious game itself was then implemented on Unity Scenes with the built models to create a gamified authentic environment that incorporates the 5 main series of steps; Screening, Contouring, External Beam Planning, Plan Evaluation, Treatment, to simulate the practical workflow of an actual Oncology treatment delivery for lung cancer patients.ConclusionThis serious game provides an educational and empirical space for training and practice that can be used by students, trainees, and professionals to expand their knowledge and skills in the aim of reducing potential errors.

Life cycle assessment of lead‐free potassium sodium niobate versus lead zirconate titanate: Energy and environmental impacts

AbstractOver the years, lead‐based piezoelectric ceramics found extensive use in vital fields such as sensors and actuators. Despite their exceptional electromechanical properties, lead‐containing materials pose severe environmental risks and foster a new era of lead‐free piezoelectric materials after decades of research. However, recent comparative assessments of potassium sodium niobate (KNN) versus lead zirconate titanate (PZT) piezoelectric materials proposed that the environmental damage already presented before use due to raw material extraction and processing, invoking concerns on the true greenness of the lead‐free alternatives. Nevertheless, many other factors deserve further consideration, for example, reference geometry and life cycle stage. Herein, the comprehensive life cycle assessment is undertaken on PZT and KNN‐based ceramics with a unit volume of 0.001 m3 from cradle to gate. Results show that PZT exhibits higher negative impacts than KNN‐based counterparts, attributed to lead extraction, processing, and associated environmental emissions. Across primary quantitative impact indicators from toxicity, environmental, and resource aspects, KNN‐based ceramics impose fewer risks on the environment and human health, with the overall impact being only 28% of PZT ceramics. Still, more efficient methods are required for KNN‐based ceramics to reduce the high energy consumption and emission during extraction and purification of raw material Nb2O5. This work not only offers critical insights for material development but also serves as a multifaceted reference for advanced fabrication technologies.image

Large-field CO (J=1-0) observations toward SNR G150.3+4.5

We aim to investigate the molecular environment of the supernova remnant (SNR) G150.3+4.5, and explore its association with ambient molecular clouds (MCs). We present large-field CO (J=1-0) molecular line observations toward SNR G150.3+4.5, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The observations have an angular resolution of $ 55 ''$. We analyzed the spatial distribution of MCs in relation to the SNR shell detected in previous Urumqi lambda 6 cm radio observations and examined the CO spectra for kinematics information. We find that MCs within the velocity range of km s$^ $ are spatially distributed along the radio shell of the SNR. Line broadening and asymmetries are observed in the CO spectra of the clouds. Moreover, we find that the molecular clouds around the shell have systematic velocity gradients in the position--velocity (PV) diagram. Both the morphology alignment and gas kinematics suggest that the SNR is associated with the ambient MCs at sim 740 pc. Based on the CO gas distance, the dimension and the age of the SNR are estimated to be 40 pc times 33 pc and 3.8 $ 10^4$ years, respectively. The very high energy emission of 1LHAASO J0428+5531 toward the SNR may originate from the interaction between the SNR and the surrounding MCs.

Evidence of Short-Lived High-Energy Emissive State and Triplet Character of the Self-Trapped Exciton in Cs3Cu2I5 Perovskite.

Cs3Cu2I5 perovskite displays a Stokes-shifted photoluminescence (PL) at 445 nm, attributed to the self-trapped excitons (STEs). Unlike that observed in other perovskite materials, the free-exciton emission is not evidenced in this case. Herein, we reveal the existence of a short-lived high-energy emission centered around 375 nm through the reconstruction of time-resolved emission spectra (TRES), which is independent of the shape/size of Cs3Cu2I5 perovskite. This high-energy emission is proposed to originate from the free-exciton-derived distorted S1 state of the 0D Cs3Cu2I5 moiety. Moreover, STE PL (∼445 nm) was found to have phosphorescence characteristics. Theoretical calculation confirms a facile intersystem crossing at the Franck-Condon geometry, indicating the high lifetime of the STE and its triplet nature. The existence of a high-energy emissive state and the phosphorescent nature of the STE PL band provide valuable insights that could advance our understanding of the photophysics in these materials.

Impact of Anisotropic Cosmic-Ray Transport on the Gamma-Ray Signatures in the Galactic Center

The very high energy (VHE) emission of the central molecular zone (CMZ) is rarely modeled in 3D. Most approaches describe the morphology in 1D or simplify the diffusion to the isotropic case. In this work, we show the impact of a realistic 3D magnetic field configuration and gas distribution on the VHE γ-ray distribution of the CMZ. We solve the 3D cosmic-ray transport equation with an anisotropic diffusion tensor using the approach of stochastic differential equations as implemented in the CRPropa framework. We test two different source distributions for five different anisotropies of the diffusion tensor, covering the range of effectively fieldline-parallel diffusion to isotropic diffusion. Within the tested magnetic field configuration, the anisotropy of the diffusion tensor is close to the isotropic case, and three point sources within the CMZ are favored. Future missions such as the upcoming CTA will reveal more small-scale structures that are not yet included in the model. Therefore, a more detailed 3D gas distribution and magnetic field structure will be needed.

Investigating X-ray emission in the GeV-emitting compact symmetric objects PKS 1718–649 and TXS 1146+596

Aims. Compact symmetric objects (CSOs) are thought to represent the first step in the evolutionary path of radio galaxies. In the present study, we investigated the X-ray emission of two CSOs confirmed to emit at GeV energies: PKS 1718–649 and TXS 1146+596. Unveiling the origin of their observed high-energy emission is crucial to establishing the physical parameters of the radio source and understanding how CSOs interact with the surrounding medium. Methods. We combined archival and new NuSTAR observations of PKS 1718–649 and TXS 1146+596 to have broadband X-ray coverage. For both sources, we modeled the broadband spectral energy distribution (SED) from the radio band up to γ-rays in order to derive their physical parameters. We also discuss the role of the ambient medium in confining the source expansion, which we investigate using X-ray obscuration. Results. For the first time, we report X-ray detections of PKS 1718–649 and 1146+596 with NuSTAR at energies higher than 10 keV. Combining Chandra and NuSTAR observations of TXS 1146+596, we reveal the presence of a multitemperature thermal component dominating the soft X-ray spectrum, and we interpret this finding as indicative of an AGN feedback process in action in this source. In addition, we show that two emitting electron populations are necessary to reproduce the observed broadband SED of TXS 1146+596: in our models, the X-ray emission could either be produced by synchrotron radiation or by a weak X-ray corona, or could be an ADAF-type emission. Interestingly, an additional X-ray component, namely a weak corona, is also required for PKS 1718–649. Moreover, we argue that heavily obscured and possibly frustrated sources tend to show different radio sizes with respect to those that are unobscured and free to expand.

Highly efficient upconversion luminescence in narrow-bandgap Y2Mo4O15.

Lanthanide-doped upconversion (UC) materials have been extensively investigated for their unique capability to convert low-energy excitation into high-energy emission. Contrary to previous reports suggesting that efficient UC luminescence (UCL) is exclusively observed in materials with a wide bandgap, we have discovered in this study that Y2Mo4O15:Yb3+/Tm3+ microcrystals, a narrowband material, exhibit highly efficient UC emission. Remarkably, these microcrystals do not display any four- or five-photon UC emission bands. This particular optical phenomenon is independent of the variation in doping ion concentration, temperature, phonon energy, and excitation power density. Combining theoretical calculations and experimental results, we attribute the vanishing emission bands to the strong interaction between the bandgap of the Y2Mo4O15 host matrix (3.37 eV) and the high-energy levels (1I6 and 1D2) of Tm3+ ions. This interaction can effectively catalyze the UC emission process of Tm3+ ions, which leads to Y2Mo4O15:Yb3+/Tm3+ microcrystals possessing very strong UCL intensity. The brightness of these microcrystals outshines commercial UC NaYF4:Yb3+,Er3+ green phosphors by a factor of 10 and is 1.4 times greater than that of UC NaYF4:Yb3+,Tm3+ blue phosphors. Ultimately, Y2Mo4O15:Yb3+/Tm3+ microcrystals, with their distinctive optical characteristics, are being tailored for sophisticated anti-counterfeiting and information encryption applications.

The variability patterns of the TeV blazar PG 1553 + 113 from a decade of MAGIC and multiband observations

ABSTRACT PG 1553 + 113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high energy (VHE; >100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low- and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required.

Constraint on Lorentz invariance violation from Vela pulsar

The High Energy Stereoscopic System (H.E.S.S.) Collaboration reported the discovery of a novel radiation component from the Vela pulsar by their Cherenkov telescopes. It is of great importance that gamma rays with energies of at least 20 TeV are recorded unexpectedly. The H.E.S.S. Collaboration argued that such results may challenge the state-of-the-art models for the high-energy emission of pulsars. We point out in this work that these results also provide a unique opportunity to constrain certain Lorentz invariance violation parameters, leading to the realization of studying Lorentz invariance violation by using gamma-ray pulsars. The Lorentz invariance violation scale is constrained at the level of 1.66\\,\ imes10^{17}$ ?> GeV for the linear scenario, and 3.53\\,\ imes10^{10}$ ?> GeV for the quadratic scenario. We anticipate that digging into the detailed features of the data of the Vela pulsar and analyzing potentially more very-high-energy photon data from pulsars in the future would improve the constraints on Lorentz invariance violation.

Very High-energy (>50 GeV) Gamma-Ray Flux Variability of Bright Fermi Blazars

Understanding the high-energy emission processes and variability patterns are two of the most challenging research problems associated with relativistic jets. In particular, the long-term (months to years) flux variability at very high energies (VHE >50 GeV) has remained an unexplored domain so far. This is possibly due to the decreased sensitivity of the Fermi Large Area Telescope (LAT) above a few GeV, hence low photon statistics, and observing constraints associated with the ground-based Cherenkov telescopes. This paper reports the results obtained from the 0.05−2 TeV Fermi-LAT data analysis of a sample of 29 blazars with the primary objective to explore their months-to-year-long very high-energy (VHE) flux variability behavior. This systematic search has led to, for the first time, the detection of significant flux variations in five blazars at the >99% confidence level, whereas eight of them exhibit variability, albeit at a lower confidence level (∼95%–99%). A comparison of the 0.05–2 TeV flux variations with that observed at 0.1–50 GeV band has revealed similar variability behavior for most of the sources. However, complex variability patterns that are not reflected contemporaneously in both energy bands were also detected, thereby providing tantalizing clues about the underlying radiative mechanisms. These results open up a new dimension to unravel the VHE emission processes operating in relativistic jets, hence sowing the seeds for their future observations with the upcoming Cherenkov Telescope Array.

Pyrolytic characteristics of abutilon stalk waste using TG-FTIR, Py-GC/MS, and artificial neural networks: Kinetics, thermodynamics, and gaseous products distribution

The physicochemical properties of abutilon stalk (ABUS) were investigated to assess its suitability for pyrolytic conversion into bioenergy and bio-based chemicals based on kinetic triplet state, thermodynamic parameters, decomposition mechanisms and product distributions. The pyrolysis behavior of ABUS was studied using a thermogravimetric analyzer at five heating rates in a nitrogen atmosphere. The Gaussian deconvolution function indicated that the pyrolysis process of ABUS can be successfully modeled as four parallel devolatilization events (R2 > 0.99), divided into the devolatilization of pseudo drying (PO-D), hemicellulose (PO-H), cellulose (PO-C), and lignin (PO-L), respectively. The average apparent activation energies were 34.89 kJ/mol for PO-D, 163.02 kJ/mol for PO-H, 169.55 kJ/mol for PO-C, and 107.51 kJ/mol for PO-L using four model-free methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Starink, and Tang). The pyrolysis process was accurately predicted using diffusional, power law, geometrical contraction, and order-based reaction mechanism models. Thermal degradation process for each devolatilization event was successfully reconstructed using combined kinetics (R2 > 0.96), providing a useful theoretical basis and mathematical model for predicting the pyrolysis behavior of ABUS. The volatile products produced by ABUS pyrolysis were characterized using an integrated TGA-FTIR and Py-GC/MS system, confirming the proportion of high-energy compounds (benzenes, phenols, ketones, alcohols, aldehydes, acids, esters, hydrocarbons and their derivatives, N-heterocyclic substances, and N-containing compounds) and gas emission levels (CO > CH4 > C-O > H2O > CO2 > CO > C-O(H) > HCN > NH3 > SO2). Artificial neural network (ANN) was used to predict the pyrolysis behaviors of ABUS, and the best ANN model was ANN (5 *11 *1) with high R2 of 0.99998. Based on the kinetics, thermodynamics, and gaseous products distribution, ABUS has great application potential as raw material for bioenergy production.

Gamma-ray detection of newly discovered Ancora supernova remnant: G288.8-6.3

The supernova remnant (SNR) was recently discovered as a faint radio shell at high Galactic latitude using observations with the Australian Square Kilometre Array Pathfinder (ASKAP) in the Evolutionary Map of the Universe (EMU) survey. We performed the first detailed investigation of the gamma -ray emission from the region, aiming to characterise the high-energy emission in the GeV regime from the newly discovered SNR, dubbed Ancora. Fifteen years of Fermi --Large Area Telescope (LAT) data were analysed at energies between MeV and TeV and the excess seen in the region was modelled using different spatial and spectral models. We detect spatially extended gamma -ray emission coinciding with the radio SNR, with detection significance up to SIsigma . A radial disk spatial model in combination with a power-law spectral model with an energy flux of pm0.91e-06 s with the spectrum extending up to around GeV was found to be the preferred model. Morphologically, hotspots seen above GeV are well correlated with the bright western part of the radio shell. The emission is more likely to be of leptonic origin, given the estimated gas density in the region and the estimated distance and age of the SNR, but a hadronic scenario cannot be ruled out. Ancora is the seventh confirmed SNR detected at high Galactic latitude with Fermi --LAT. The study of this new population of remnants can provide insights into the evolutionary aspects of SNRs and their properties, and further advance efforts of constraining the physics of particle diffusion and escape from SNRs into the Galaxy.

The physical properties of Fermi-4LAC low-synchrotron-peaked BL Lac objects

ABSTRACT Previous studies on the fitting of spectral energy distributions (SEDs) often apply the external-Compton process to interpret the high-energy peak of low-synchrotron-peaked (LSP) BL Lac objects (LBLs), despite the lack of strong broad emission lines observed for LBLs. In this work, we collect quasi-simultaneous multiwavelength data of 15 LBLs from the Fermi fourth LAT AGN catalogue (4LAC). We propose an analytical method to assess the necessity of external photon fields in the framework of one-zone scenario. Following derived analytical results, we fit the SEDs of these LBLs with the conventional one-zone leptonic model and study their jet physical properties. Our main results can be summarized as follows. (1) We find that most LBLs cannot be fitted by the one-zone synchrotron-self-Compton (SSC) model. This indicates that external photons play a crucial role in the high-energy emission of LBLs, therefore we suggest that LBLs are masquerading BL Lacs. (2) We suggest that the γ-ray emitting regions of LBLs are located outside the broad-line region and within the dusty torus. (3) By extending the analytical method to all types of LSPs in Fermi-4LAC (using historical data), we find that the high-energy peaks of some flat spectrum radio quasars and blazar candidates of unknown types can be attributed to the SSC emission, implying that the importance of external photons could be minor. We suggest that the variability time-scale may help distinguish the origin of the high-energy peak.

Rethinking the 67 Hz QPO in GRS 1915+105: Type C quasi-periodic oscillations at the innermost stable circular orbit

We study quasi-periodic oscillations (QPO) at low and high frequency in the variability of the high-energy emission from black hole binaries and their physical interpretation in terms of signatures of General Relativity in the strong-field regime. We wish to understand the nature of the 67 Hz QPOs observed in the X-ray emission of the peculiar black hole binary GRS 1915+105 within the general classification of QPOs, and to determine the spin of the black hole in the system by applying the relativistic precession model (RPM). Within the RPM, the only relativistic frequency that is stable in time over a wide range of accretion rates and can be as low as 67 Hz (for a dynamically measured black hole mass) is the nodal frequency at the innermost stable circular orbit (ISCO). In the application of the model, this corresponds to type C QPOs. Under this assumption, it is possible to measure the spin of the black hole by using the mass of the black hole previously obtained via dynamical measurements. We re-analysed a large number of RossiXTE observations to determine whether other timing features confirm this hypothesis. The identification of the 67 Hz QPO as the nodal frequency at ISCO yields a value of 0.706 pm 0.034 for the black hole spin. With this spin, the only two QPO detections at higher frequencies available in the literature are consistent with being orbital frequencies at a radius outside ISCO. The high-frequency bumps often observed at frequencies between 10 and 200 Hz follow the correlation expected for orbital and periastron-precession frequencies at even larger radii.

Yet Another Sunshine Mystery: Unexpected Asymmetry in GeV Emission from the Solar Disk

The Sun is one of the most luminous γ-ray sources in the sky and continues to challenge our understanding of its high-energy emission mechanisms. This study provides an in-depth investigation of the solar disk γ-ray emission, using data from the Fermi Large Area Telescope spanning 2008 August to 2022 January. We focus on γ-ray events with energies exceeding 5 GeV, originating from 0.°5 angular aperture centered on the Sun, and implement stringent time cuts to minimize potential sample contaminants. We use a helioprojection method to resolve the γ-ray events relative to the solar rotation axes and combine statistical tests to investigate the distribution of events over the solar disk. We found that integrating observations over large time windows may overlook relevant asymmetrical features, which we reveal in this work through a refined time-dependent morphological analysis. We describe significant anisotropic trends and confirm compelling evidence of energy-dependent asymmetry in the solar disk γ-ray emission. Intriguingly, the asymmetric signature coincides with the Sun’s polar field flip during the cycle 24 solar maximum, around 2014 June. Our findings suggest that the Sun’s magnetic configuration plays a significant role in shaping the resulting γ-ray signature, highlighting a potential link between the observed anisotropies, solar cycle, and the solar magnetic fields. These insights pose substantial challenges to established emission models, prompting fresh perspectives on high-energy solar astrophysics.

First characterization of the emission behavior of Mrk 421 from radio to very high-energy gamma rays with simultaneous X-ray polarization measurements

We have performed the first broadband study of Mrk 421 from radio to TeV gamma rays with simultaneous measurements of the X-ray polarization from IXPE. The data were collected as part of an extensive multiwavelength campaign carried out between May and June 2022 using MAGIC Fermi -LAT NuSTAR XMM-Newton Swift and several optical and radio telescopes to complement IXPE data. During the IXPE exposures, the measured 0.2–1 TeV flux was close to the quiescent state and ranged from 25<!PCT!> to 50<!PCT!> of the Crab Nebula without intra-night variability. Throughout the campaign, the very high-energy (VHE) and X-ray emission are positively correlated at a $4 significance level. The IXPE measurements reveal an X-ray polarization degree that is a factor of 2-5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the VHE photons are emitted co-spatially with the X-rays, in the vicinity of a shock front. The June 2022 observations exhibit a rotation of the X-ray polarization angle. Despite no simultaneous VHE coverage being available during a large fraction of the swing, the Swift -XRT monitoring reveals an X-ray flux increase with a clear spectral hardening. This suggests that flares in high synchrotron peaked blazars can be accompanied by a polarization angle rotation, as observed in some flat spectrum radio quasars. Finally, during the polarization angle rotation NuSTAR data reveal two contiguous spectral hysteresis loops in opposite directions (clockwise and counterclockwise), implying important changes in the particle acceleration efficiency on approximately hour timescales.

Chandra/HETG Doppler velocity measurements in stellar coronal sources

ABSTRACT Stellar coronal sources have been observed in the past not only for their astrophysical interest in the field of binary system evolution and interaction but also for their invaluable roles as benchmarks for plasma spectral models and as calibration sources for high resolution spectroscopic X-ray instruments. These include the gratings on-board Chandra and XMM-Newton, as well as the new generation of high resolution capable-detectors recently flown on-board XRISM and planned for the future also onboard the Athena and the LEM missions. In our previous paper exploiting Chandra/HETG observations of the prototypical coronal source Capella, it has been shown that the centroid energies of the many X-ray emission lines detected in the spectrum of this object change as a function of time due to the Doppler modulation within the binary. This is an effect that needs to be corrected while performing calibrations of high-resolution X-ray instruments. In this paper, we extend our previous work on Capella to other known stellar coronal sources that have been observed with the Chandra/HETG (11 objects in total). We measure in several objects clear trends in the velocity shifts along the orbit of the primary star, meaning that in these sources one of the two star components is largely dominating the high energy emission. In a number of systems the trend in the velocity shift is not obvious. This can be ascribed to the fact that both stellar components contribute significantly to the X-ray emission.

Could a Kilonova Kill: A Threat Assessment

Binary neutron star mergers produce high-energy emissions from several physically different sources, including a gamma-ray burst (GRB) and its afterglow, a kilonova (KN), and, at late times, a remnant many parsecs in size. Ionizing radiation from these sources can be dangerous for life on Earth-like planets when located too close. Work to date has explored the substantial danger posed by the GRB to on-axis observers; here we focus instead on the potential threats posed to nearby off-axis observers. Our analysis is based largely on observations of the GW170817/GRB 170817A multi-messenger event, as well as theoretical predictions. For baseline KN parameters, we find that the X-ray emission from the afterglow may be lethal out to ∼1 pc and the off-axis gamma-ray emission may threaten a range out to ∼4 pc, whereas the greatest threat comes years after the explosion, from the cosmic rays accelerated by the KN blast, which can be lethal out to distances up to ∼11 pc. The distances quoted here are typical, but the values have significant uncertainties and depend on the viewing angle, ejected mass, and explosion energy in ways we quantify. Assessing the overall threat to Earth-like planets, KNe have a similar kill distance to supernovae, but are far less common. However, our results rely on the scant available KN data, and multi-messenger observations will clarify the danger posed by such events.

Simulating gamma-ray production from cosmic rays interacting with the solar atmosphere in the presence of coronal magnetic fields* *Supported in China by the NSFC (12261160362, 12022502). KCYN is supported by grants provided by the NSFC (12322517, N_CUHK456/22) and RGC (24302721, 14305822, 14308023)

Cosmic rays can interact with the solar atmosphere and produce a slew of secondary messengers, making the Sun a bright gamma-ray source in the sky. Detailed observations with Fermi-LAT have shown that these interactions must be strongly affected by solar magnetic fields in order to produce a wide range of observational features, such as a high flux and hard spectrum. However, the detailed mechanisms behind these features are still a mystery. In this study, we tackle this problem by performing particle-interaction simulations in the solar atmosphere in the presence of coronal magnetic fields using the potential field source surface (PFSS) model. We find that low-energy (~ GeV) gamma-ray production is significantly enhanced by the coronal magnetic fields, but the enhancement decreases rapidly with energy. The enhancement directly correlates with the production of gamma rays with large deviation angles relative to the input cosmic-ray direction. We conclude that coronal magnetic fields are essential for correctly modeling solar disk gamma rays below 10 GeV, but above that, the effect of coronal magnetic fields diminishes. Other magnetic field structures are needed to explain the high-energy disk emission.

The X-ray high-energy cutoff in compact symmetric object Mrk 348

ABSTRACT Compact radio active galactic nuclei (AGNs) are thought to be young radio AGN at the early stage of AGN evolution, thus are ideal laboratory to study the high-energy emission throughout the evolution of radio AGN. In this work, we report for the first time the detection of the high-energy cutoff (Ecut), a direct indicator of thermal coronal radiation, of X-ray emission in Mrk 348 (z = 0.015), a young radio galaxy classified as compact symmetric object. With a 100 ks Nuclear Spectroscopic Telescope Array exposure, we find that the high-energy cutoff (Ecut) is firmly detected ($218^{+124}_{-62}$ keV). Fitting with various Comptonization models indicates the presence of a hot corona with temperature kTe = 35–40 keV. These strongly support the corona origin for its hard X-ray emission. The comparison in the Ecut – spectra index Γ plot of Mrk 348 with normal large-scale radio galaxies (mostly Fanaroff–Riley type II) yields no difference between them. This suggests the corona properties in radio sources may not evolve over time (i.e. from the infant stage to mature stage), which is to-be-confirmed with future sample studies of young radio AGNs.