High-energy Component Research Articles

Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A

Abstract We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.°2 away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on 2021 December 8. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV γ-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the γ-ray data from Fermi-LAT, VERITAS, and H.E.S.S. require a spectral cutoff near 100 GeV. Both the X-ray and γ-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed γ-ray spectral cutoff in both the leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power.

Gamma-ray Emission and Variability Processes in High-Energy-Peaked BL Lacertae Objects

BL Lac objects are active galactic nuclei notable for a beamed nonthermal radiation, which is generated in one of the relativistic jets forming a small angle to the observer’s line-of-sight. The broadband spectra of BL Lacs show a two-component spectral energy distribution (SED). High-energy-peaked BL Lacs (HBLs) exhibit their lower-energy (synchrotron) peaks at UV to X-ray frequencies. The origin of the higher-energy SED component, representing the γ-ray range in HBLs, is still controversial and different emission scenarios (one- and multi-zone synchrotron self-Compton, hadronic etc.) are proposed. In γ-rays, HBLs show a complex flaring behavior with rapid and large-amplitude TeV-band variations on timescales down to a few minutes. This review presents a detailed characterization of the hypothetical emission mechanisms which could contribute to the γ-ray emission, their application to the nearby TeV-detected HBLs, successes in the broadband SED modeling and difficulties in the interpretation of the observational data. I also overview the unstable processes to be responsible for the observed γ-ray variability and particle energization up to millions of Lorentz factors (relativistic shocks, magnetic reconnection, turbulence and jet-star interaction). Finally, the future prospects for solving the persisting problems by means of the dedicated gamma-ray observations and sophisticated simulations are also addressed.

Effects of multiple laser shock peening impacts on microstructure and wear performance of wire-based laser directed energy deposition 17-4PH stainless steel

As an advanced surface-strengthening technology, laser shock peening (LSP) is suitable for strengthening high-energy beam additive manufacturing components by improving the uneven temperature distribution and mechanical anisotropy problems. The present study investigated the influence of multiple LSP impacts on the microstructure evolution and wear performance of wire-based laser directed energy deposition (LDED) 17-4 PH stainless steel. Results showed that with the increase of LSP impacts, the average grain size of the wire-based LDED layer decreases and the dislocation density increases. Meanwhile, the residual stress was completely converted from tensile state to compressive state, and reaches the maximum value of 424 ± 15 MPa. In addition, the significant improvement of microhardness and wear resistance after 3 LSP impacts is attributed to the combined effects of grain refinement and dislocation strengthening.

Structural modal identification and enhancement of low-energy modes by successively variational extraction of high-energy modes

Accurate identification of modal properties for as much as possible modes from structural monitoring responses is an important part for structural health monitoring systems. Limited by the energy of external excitations, or influenced by the heavy noise, the energies of some modal components may be weak or buried in the energy of noise, giving rise to the difficulty for accurate modal identification. Variational mode decomposition method is a non-recursive decomposing procedure to decompose a signal into narrow-band sub-components. However, the difficulty for the decomposition of low-energy mode is determining the corresponding initial center frequencies. In this study, a new method for low-energy mode identification is proposed using the idea of locating, identifying, and subtracting the high-energy component to gradually enlarge the relative energy level of low-energy mode by substituting the original signal with residual signal repeatedly. First, the initial center frequency of the mode with maximum energy is determined by autoregressive power spectrum; second, the modal parameters including frequency, damping ratio and mode shape are identified by the singular value decomposition of Hankel matrix with low system order; third, vibrational mode extraction method is proposed to extract the modal component with maximum energy; subsequently, the modal component with maximum energy is subtracted from the original signal to construct the residual signal for the identification of next maximum energy component. The relative energy level of low-energy mode is enlarged gradually by repeating the subtraction of high-energy modal component. Then, the accuracy of low-energy mode identification is improved. The effectiveness of the proposed method is verified by the simulated structures under ambient and earthquake excitations with high-level noises. Besides, the capability for the application of practical structure is verified by the experimental data of a real bridge.

A new high energy but low explosion temperature gun propellant component: nitrogen-rich tetrazole derivative grafted nitrocellulose

In order to apply the high nitrogen-content tetrazole derivatives (TZD), a class of energy materials with great potential, into gun propellant, we propose a novel idea that grafting the acidized TZD onto cellulose and then nitrifying the grafted cellulose to obtain nitrocellulose grafted by TZD (TZDNC). Theoretical predictions suggest that Replacing nitrocellulose (NC) with TZDNC, due to having higher nitrogen-content of TZDNC than traditional NC, can evidently reduce the ablation to gun tube, smoke and flame around muzzle of gun tube. The replacement not only solves the incompatibility of TZD with the other components such as NG, RDX and HMX, but maintains the nearly gun powder power of gun propellant before replacing.

Time-Domain Rotational Raman Spectroscopy of the Ethylene Dimer and Trimer by Coulomb Explosion Imaging of Rotational Wave Packets.

We report rotational Raman spectroscopy of the ethylene dimer and trimer, based on time-resolved Coulomb explosion imaging of rotational wave packets. Rotational wave packets were created in the gas-phase ethylene clusters upon nonresonant ultrashort pulse irradiation. The subsequent rotational dynamics were traced as spatial distribution of monomer ions ejected from the clusters via the Coulomb explosion process induced by a strong probe pulse. The observed images of monomer ions show multiple kinetic energy components. The time-dependence of the angular distribution for each component was analyzed, and the Fourier transformation spectra, which correspond to rotational spectra, were obtained. A lower kinetic energy component was mainly attributed to a signal from the dimer and a higher energy component mainly from the trimer. We have successfully observed rotational wave packets up to a delay time of ∼20 ns and achieved a spectral resolution of 70 MHz after Fourier transformation. Owing to this higher resolution than the previous studies, improved rotational and centrifugal distortion constants were obtained from the spectra. In addition to improving the spectroscopic constants, this study opens the way for rotational spectroscopy of larger molecular clusters than dimers through Coulomb explosion imaging of rotational wave packets. Details of spectral acquisition and analyses of each kinetic energy component are also reported.

Cosmic neutrons at ground: new spectral measurements at 3480 m a.s.l. and benchmarking of the cascade component as a function of the elevation at around 45° geomagnetic latitude

Within the INFN-based project SAMADHA, environment neutron spectrum measurements were performed at 3480 m a.s.l. on the Italian western Alps. An extended range Bonner Sphere Spectrometer was used, that was especially designed to operate unattended and to discriminate genuine neutron events from spurious ones. In addition to the measurements of neutron fluence rate, its energy distribution and the related ambient dose equivalent, as well as the arrival time distribution of the events were also studied. The high-energy component of the neutron fluence rate was compared to literature data measured with the same technique at similar latitudes as a function of the elevation, in turn being fitted with an exponential curve and compared to the results from EXPACS code. As the cascade component is not influenced by the materials surrounding the measurement site, this curve can be regarded as “universal” at the studied latitudes.

X-ray fluorescence (XRF) analysis and prediction of induced radioactivity components for high-energy electron accelerator

The objective of this research was to predict the induced activation in high-energy particle accelerator components to determine the isotope inventories and remanent dose rates for considering the replacement materials. The long-lived radionuclides produced by nuclear reactions caused biological health effects to human as well as environmental impacts. The bremsstrahlung photon beam by the high-energy electron accelerator produced the radioactive nuclei from direct interactions or indirect interactions. The study highlighted the determination of chemical compositions and the estimation of induced activation in particle accelerator components. The elemental compositions of materials were investigated by the X-ray fluorescence (XRF) technique. The heavy metal elements were detected with different percentages, i.e., Zr, Zn, Ti, Pb, Ni, Mn, Fe and Cu. To calculate the induced activation in the materials, the FLUKA simulation was performed. The 1.2 GeV high-energy electron beam had been defined to irradiate the materials for this simulation. The daughter nuclei were obtained, and their decay followed. The estimation of the residual dose rate in activated materials after various cooling times from the end of the irradiation was presented.

Photometry and spectroscopy of the Type Icn supernova 2021ckj

We present photometric and spectroscopic observations of the Type Icn supernova (SN) 2021ckj. This rare type of SNe is characterized by a rapid evolution and high peak luminosity as well as narrow lines of highly ionized carbon at early phases, implying an interaction with hydrogen- and helium-poor circumstellar matter (CSM). SN 2021ckj reached a peak brightness of ∼ − 20 mag in the optical bands, with a rise time and a time above half maximum of ∼4 and ∼10 days, respectively, in the g and cyan bands. These features are reminiscent of those of other Type Icn SNe (SNe 2019hgp, 2021csp, and 2019jc), with the photometric properties of SN 2021ckj being almost identical to those of SN 2021csp. Spectral modeling of SN 2021ckj reveals that its composition is dominated by oxygen, carbon, and iron group elements, and the photospheric velocity at peak is ∼10 000 km s−1. Modeling the spectral time series of SN 2021ckj suggests aspherical SN ejecta. From the light curve (LC) modeling applied to SNe 2021ckj, 2019hgp, and 2021csp, we find that the ejecta and CSM properties of Type Icn SNe are diverse. SNe 2021ckj and 2021csp likely have two ejecta components (an aspherical high-energy component and a spherical standard-energy component) with a roughly spherical CSM, while SN 2019hgp can be explained by a spherical ejecta-CSM interaction alone. The ejecta of SNe 2021ckj and 2021csp have larger energy per ejecta mass than the ejecta of SN 2019hgp. The density distribution of the CSM is similar in these three SNe, and is comparable to those of Type Ibn SNe. This may imply that the mass-loss mechanism is common between Type Icn (and also Type Ibn) SNe. The CSM masses of SN 2021ckj and SN 2021csp are higher than that of SN 2019hgp, although all these values are within those seen in Type Ibn SNe. The early spectrum of SN 2021ckj shows narrow emission lines from C II and C III, without a clear absorption component, in contrast with that observed in SN 2021csp. The similarity of the emission components of these lines implies that the emitting regions of SNe 2021ckj and 2021csp have similar ionization states, and thus suggests that they have similar properties as the ejecta and CSM, which is also inferred from the LC modeling. Taking the difference in the strength of the absorption features into account, this heterogeneity may be attributed to viewing angle effects in otherwise common aspherical ejecta. In particular, in this scenario SN 2021ckj is observed from the polar direction, while SN 2021csp is seen from an off-axis direction. This is also supported by the fact that the late-time spectra of SNe 2021ckj and 2021csp show similar features but with different line velocities.

General Physical Properties of Gamma-Ray-emitting Radio Galaxies

We study the radio galaxies with known redshifts detected by the Fermi satellite after 10 yr of data (4FGL-DR2). We use a one-zone leptonic model to fit the quasi-simultaneous multiwavelength data of these radio galaxies and study the distributions of the derived physical parameters as a function of black hole mass and accretion disk luminosity. The main results are as follows. (1) We find that the jet kinetic power of most radio galaxies can be explained by the hybrid jet model based on ADAFs surrounding Kerr black holes. (2) After excluding the redshift, there is a significant correlation between the radiation jet power and the accretion disk luminosity, while the jet kinetic power is weakly correlated with the accretion disk luminosity. (3) We also find a significant correlation between inverse Compton luminosity and synchrotron luminosity. The slope of the correlation for radio galaxies is consistent with the synchrotron self-Compton (SSC) process. The result may suggest that the high-energy components of radio galaxies are dominated by the SSC process.

The opportunities of using a natural adaptogen from the <i>Galleria mellonella</i> larvae in veterinary medicine

A comparative analysis of the adaptation effects of the Porsolt test of fractionated solutions obtained from the products of the larvae of the large wax moth (Galleria mellonella) on biological systems was performed. The method of X-ray photoelectron spectroscopy determined that in the obtained light fraction of the products of larval life there is a high-energy component of N1s spectra (~402.0 eV) and bond energy for carbon in the C-N bond (~286.0 eV), which indicates the presence of protonated amino groups in the samples. Absorption at 1700 cm-1 can be attributed to the presence of dicarboxylic amino acids (glutamic and aspartic) and other organic acids, which are much less in the heavy fraction. During oral administration of the studied extracts, their multidirectional effect on the intestines of laboratory mice was found. The negative effect of heavy fraction on the microbiocenosis of the intestine by the qualitative composition of the microflora was detected. When the light fraction is used, the intestinal microflora is close to the control. Analysis of the number of leukocytes of the small intestine when the fractions were injected reflected the local immune response of the body. The content of these cells on the mucosal plate of mice injected with the lung fraction was 67.2% higher than that of the control mice (p ≤ 0.05). The content of leukocytes on the own plate of the mucosa of mice injected with the heavy fraction was 2.7 times higher compared to the control, indicating an inflammatory reaction. The difference between the experimental groups is significant (p ≤ 0.001). The comparative effect of the fractions showed that their oral administration had a different effect on the swimming time compared to the control. After 20 days of the experiment, mice injected with the heavy fraction had significantly increased their swimming time compared to the first day (p ≤ 0.05). However, a negative adaptogenic effect compared to the control group is noticeable. A significant difference was found between the results on the 30th day between the experimental groups, which indicates a pronounced difference in the results obtained.

Complex of Mn(II) Perchlorate with (2-Methylenepropane-1,3-diyl)bis(diphenylphosphine Oxide): Synthesis, Structure, and Double Luminescence

The reaction of Mn(ClO4)2·6H2O with (2-methylenepropan-1,3-diyl)bis(diphenylphosphine oxide) (L) in a methanol medium yielded a previously unknown complex [MnL2(MeOH)2](ClO4)2. According to X-ray diffraction data, its Mn2+ ion has a distorted octahedral environment formed by two chelate L ligands and two coordinated methanol molecules. At 298 K, this complex exhibits low-intensity dual luminescence, the low-energy component of which is attributed to Mn2+-centered phosphorescence, and the high-energy component is assigned to intraligand fluorescence.

Damage-free LED lithography for atomically thin 2D material devices

Desired electrode patterning on two-dimensional (2D) materials is a foremost step for realizing the full potentials of 2D materials in electronic devices. Here, we introduce an approach for damage-free, on-demand manufacturing of 2D material devices using light-emitting diode (LED) lithography. The advantage of this method lies in mild photolithography by simply combining an ordinary optical microscope with a commercially available LED projector; the low-energy red component is utilized for optical characterization and alignment of devices, whereas the high-energy blue component is utilized for photoresist exposure and development of personal computer designed electrode patterns. This method offers maskless, damage-free photolithography, which is particularly suitable for 2D materials that are sensitive to conventional lithography. We applied this LED lithography to device fabrication of selected nanosheets (MoS2, graphene oxides and RuO2), and achieved damage-free lithography of various patterned electrodes with feature sizes as small as 1–2 μm. The LED lithography offers a useful approach for cost-effective mild lithography without any costly instruments, high vacuum, or complex operation.

Study on Pseudospark Switch Triggered by 532-nm Focused Laser

The influence of laser energy, irradiation position, photoelectric material, and anode voltage on the trigger characteristics of a pseudospark switch triggered by a 532-nm nanosecond focused laser is studied. The parameters of the seed electrons induced by the interaction between the focused laser and metal are measured. It is found that the increase of laser energy and anode voltage can increase the current density of seed electrons, reduce the time of electrons diffusion to the cathode hole, and thus reduce the trigger delay. When the irradiation position is close to the cathode hole, the surface electric field is larger, which is conducive to achieving a smaller trigger delay and jitter under low laser energy. The seed electron current induced by the focused laser has two peaks. The first peak mainly corresponds to the thermal emission, with a short time delay and narrow pulsewidth, contributing to the trigger. The second peak mainly corresponds to the electrode surface ablation, with a long time delay and large pulsewidth, contributing little to the trigger. In this case, the electrode surface temperature is more important than the work function, so Cu has better electron emission characteristics than Mg. With the increase of laser energy, the number of electrons in high-energy components increases.

Simulation of the spatio-temporal evolution of the electron energy distribution function in a pulsed hollow-cathode discharge

This article presents the 2D simulation results of a nanosecond pulsed hollow cathode discharge obtained through a combination of fluid and kinetic models. The spatio-temporal evolution of the electron energy distribution function (EEDF) of the plasma column and electrical characteristics of the nanosecond pulsed hollow cathode discharge at a gas pressure of 5 Torr are studied. The results show that the discharge development starts with the formation of an ionization front at the anode surface. The ionization front splits into two parts in the cathode cavity while propagating along its lateral surfaces. The ionization front formation leads to an increase in the fast isotropic EEDF component at its front, as well as in the anisotropic EEDF component. The accelerated electrons enter the cathode cavity, which significantly contributes to the formation of the high-energy EEDF component and EEDF anisotropy.

INTEGRAL study of MAXI J1535−571, MAXI J1820+070, and MAXI J1348 − 630 outbursts

In black hole X-ray binaries, a nonthermal high-energy component is sometimes detected at energies above 200 keV. The origin of this high-energy component is debated and distinct spectral modelizations can lead to different interpretations. High-energy polarimetry measurements with the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) enable new diagnostics on the physics responsible for the MeV spectral component in black hole X-ray binaries. In this work, we aim to investigate the high-energy behavior of three bright sources discovered by the Monitor of All-sky X-ray Image: MAXI J1535−571, MAXI J1820+070, and MAXI J1348−630. We took advantage of their brightness to investigate their soft γ-ray (0.1–2 MeV) properties with INTEGRAL. We used both spectral and polarimetric approaches to probe their high-energy emission with the aim of bringing new constraints on the MeV emission in black hole X-ray binaries. We first studied the spectral characteristics of the sources in the 3–2000 keV range using JEM-X, IBIS, and SPI, with a semi-phenomenological description of the data. We then used IBIS as a Compton telescope in order to evaluate the polarization properties of the sources above 300 keV. A high-energy component was detected during the hard-intermediate state and soft-intermediate state of MAXI J1535−571, the low-hard state of MAXI J1820+070, and the low-hard state of MAXI J1348−630. The components detected in MAXI J1820+070 and MAXI J1348 − 630 were polarized with a polarization fraction of 26 ± 9° and > 56% in the 300–1000 keV range, respectively. With no polarization information for MAXI J1535−571, the component detected could either come from the jets or the corona. In the case of MAXI J1820+070, the extrapolation of the synchrotron spectrum measured in the infrared indicates that the component is likely due to a nonthermal distribution of electrons from a hybrid corona. For MAXI J1348−630, the high fraction of polarization points toward a jets origin; however, we cannot formally conclude this without any infrared data giving information on the optically thin part of the synchrotron spectrum.

Measurements of Cosmic Ray Mass Composition with the IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a multi-component detector at the South Pole. Besides studying high-energy neutrinos, it is capable of measuring high-energy cosmic rays from PeV to EeV. This energy region is thought to cover the transition from galactic to extragalactic sources of cosmic rays. The observatory consists of the deep in-ice IceCube array, which measures the high-energy (≥500 GeV) muonic component, and the IceTop surface array, which is sensitive to the electromagnetic and low-energy muonic part of an air shower. The primary energy and the mass composition can be measured simultaneously by applying statistical methods including modern machine-learning techniques to reconstruct cosmic ray air showers. In this contribution, we will discuss recent improvements to the reconstruction techniques, the mass composition sensitivity, and an outlook on future improved measurements with the full surface scintillator/radio array to mitigate snow accumulation and measure the air shower maximum Xmax using imaging air-Cherenkov telescopes IceAct.

New approaches for gamma-hadron separation at the IceCube Neutrino Observatory

The IceCube Neutrino Observatory located at the geographic South Pole is composed of two detectors. One is the in-ice optical array, which measures high-energy muons from air showers and charged particles produced by the interaction of high-energy neutrinos in the ice. The other is an array of ice-Cherenkov tanks at the surface, called IceTop, which is used both as veto for the in-ice neutrino measurements and for detecting cosmic-ray air showers. In the next decade, the IceCube-Gen2 extension will increase the surface coverage including surface radio antennas and scintillator panels on the footprint of an extended optical array in the ice. The combination of the current surface and in-ice detectors can be exploited for the study of cosmic rays and the search for PeV gamma rays. The in-ice detector measures the high-energy muonic component of air showers, whereas the signal in IceTop is dominated by the electromagnetic component. The relative size of the muonic and electromagnetic components is different for gamma-and hadron-induced air showers. Thus, the gamma-hadron separation of cosmic rays is attempted using machine learning techniques including deep learning. Here, different approaches are presented. Finally, the prospects for the detection of PeV photons with IceCube-Gen2 will be discussed.

Dissociative ionization and Coulomb explosion of CH4 in two-color asymmetric intense laser fields.

Directional fragment ejection from a tetrahedral molecule CH4 in linearly polarized two-color (ω and 2ω) asymmetric intense laser fields (50 fs, 1.4 × 1014 W cm-2, 800 nm and 400 nm) has been studied by three-dimensional ion coincidence momentum imaging. The H+ fragment produced from dissociative ionization, CH4 → H+ + CH3 + e-, is preferentially ejected on the larger amplitude side of the laser electric fields. Comparison with theoretical predictions by weak-field asymptotic theory shows that the observed asymmetry can be understood by the orientation selective tunneling ionization from the triply degenerated highest occupied molecular orbital (1t2) of CH4. A similar directional ejection of H+ was also observed for the low kinetic energy components of the two-body Coulomb explosion, CH4 → H+ + CH3+ + 2e-. On the other hand, the fragment ejection in the opposite direction were observed for the high energy component, as well as H2+ produced from the Coulomb explosion CH4 → H2+ + CH2+ + 2e-. Possible origins of the characteristic fragmentation are discussed.

On the Hadronic Origin of High-energy Emission of γ-Ray-loud Narrow-line Seyfert 1 PKS 1502+036

The radiation mechanism of Radio-Loud Narrow-Line Seyfert 1 (RL-NLS1) galaxies from X-ray to γ-ray bands remains an open question. While the leptonic model has been employed to explain the spectral energy distribution (SED), the hadronic process may potentially account for the high-energy radiation of some γ-ray-loud Narrow-Line Seyfert 1 (NLS1) galaxies as well. We study one of such RL-NLS1s, PKS 1502+036, comparing the theoretical SEDs predicted by the leptonic model and the lepto-hadronic model to the observed one. For the hadronic processes, we take into account the proton synchrotron radiation and proton–photon interactions (including the Bethe–Heitler process and the photopion process) including the emission of pairs generated in the electromagnetic cascade initiated by these processes. Our results show that the leptonic model can reproduce the SED of this source, in which the X-ray to γ-ray radiation can be interpreted as the inverse Compton scattering. On the other hand, the proton synchrotron radiation can also explain the high-energy component of SED although extreme parameters are needed. We also demonstrate that the p γ interactions as well as the cascade process cannot explain SED. Our results imply that a leptonic origin is favored for the multiwavelength emission of PKS 1502+036.