X-ray Emission Research Articles

Mapping AGN winds: A connection between radio-mode AGNs and the AGN feedback cycle

We present a kinematic analysis based on the large integral field spectroscopy (IFS) dataset of SDSS-IV MaNGA (Sloan Digital Sky Survey/Mapping Nearby Galaxies at Apache Point Observatory; ∼10 000 galaxies). We have compiled a diverse sample of 594 unique active galactic nuclei (AGNs), identified through a variety of independent selection techniques, encompassing radio (1.4 GHz) observations, optical emission-line diagnostics (BPT), broad Balmer emission lines, mid-infrared colors, and hard X-ray emission. We investigated how ionized gas kinematics behave in these different AGN populations through stacked radial profiles of the [O III] 5007 emission-line width across each AGN population. We contrasted AGN populations against each other (and non-AGN galaxies) by matching samples by stellar mass, [O III] 5007 luminosity, morphology, and redshift. We find similar kinematics between AGNs selected by BPT diagnostics compared to broad-line-selected AGNs. We also identify a population of non-AGNs with similar radial profiles as AGNs, indicative of the presence of remnant outflows (or fossil outflows) of past AGN activity. We find that purely radio-selected AGNs display enhanced ionized gas line widths across all radii. This suggests that our radio-selection technique is sensitive to a population in which AGN-driven kinematic perturbations have been active for longer durations (potentially due to recurrent activity) than in purely optically selected AGNs. This connection between radio activity and extended ionized gas outflow signatures is consistent with recent evidence that suggests radio emission (expected to be diffuse) originated due to shocks from outflows. We conclude that different selection techniques can trace different AGN populations not only in terms of energetics but also in terms of AGN evolutionary stages. Our results are important in the context of the AGN duty cycle and highlight integral field unit data’s potential to deepen our knowledge of AGNs and galaxy evolution.

Novel method for quantifying the ratios of sp3/sp2 hybridized carbon in diamond-like carbon films using soft X-ray emission spectroscopy

This study presents a pioneering method for quantifying the ratios of sp3/sp2 hybridized carbon in diamond-like carbon (DLC) films. The novelty lies in using soft X-ray emission spectroscopy (SXES), a technique not widely employed in this context. The DLC films, obtained through various deposition methods, were characterized for hydrogen content, film density, and sp3/sp2 ratio using Rutherford backscattering spectroscopy/Elastic recoil detection analysis (RBS/ERDA), X-ray reflectivity (XRR), and SXES, respectively. To ensure the reliability of the SXES method, it was validated through comparative analysis with near-edge X-ray absorption fine Structure (NEXAFS) spectroscopy, providing confidence in its accuracy. While NEXAFS provided consistent sp3/sp2 ratio measurements in hydrogen-free DLC films, its accuracy in hydrogenated DLC films was impacted due to poor accuracy when applied to this film group. In contrast, SXES demonstrated greater precision in hydrogenated and hydrogen-free DLC films, revealing sp3/sp2 ratios ranging from 36 % to 62 %, corresponding variations in hydrogen contents and film densities. These findings highlight the superior utilization of SXES in accurately determining the sp3- and sp2-hybridized carbon ratios, particularly in hydrogenated DLC films, offering a robust alternative to NEXAFS and paving the way for enhanced characterization and application in various industrial fields.

Initial results of hard X-ray spectroscopy by LaBr[formula omitted](Ce) detector for runaway electron study in Thailand Tokamak-1

Thailand Tokamak-1 (TT-1) successfully achieved its first plasma operation in early 2023. Understanding the behavior of high-energy runaway electrons (RE) during plasma discharges is crucial in TT-1 due to the potential risk of significant damage to in-vessel components. To study the RE behavior and analyze its characteristics, the LaBr3(Ce) detector was employed for measuring hard X-ray emissions in TT-1. In this study, we first characterized the LaBr3(Ce) detector in the laboratory and then performed hard X-ray spectroscopy in TT-1. Calibration sources, including 133Ba, 137Cs, 22Na, and 60Co, with energies up to 1.33 MeV, were used in the laboratory. The detector was calibrated using biased high voltage of -1000 V. It was found to have an energy resolution of approximately 6.2% at an energy of 0.662 MeV. After calibration, the detector was installed at TT-1 to measure hard X-ray. We analyze the hard X-ray emission from discharge #2183 during a selected time interval. It is found that the high-energy hard X-ray emissions reach up to approximately 500 keV. Assuming a simple Maxwellian distribution of the RE population, their temperature is estimated to be 224±5 keV. These findings confirm the presence of high-energy runaway electrons during TT-1’s plasma discharges. However, to accurately derive the runaway electron energy spectrum from the hard X-ray energy spectrum, the unfolding technique is required. In future work, we plan to apply the unfolding method, conduct numerical simulations on the physics of runaway electrons, and employ Monte Carlo simulations on the hard X-ray emissions.

An X-ray flaring event and a variable soft X-ray excess in the Seyfert LCRS B040659.9–385922 as detected with eROSITA

Context. Extreme continuum variability in extragalactic nuclear sources can indicate extreme changes in accretion flows onto supermassive black holes. Aims. We explore the multiwavelength nature of a continuum flare in the Seyfert LCRS B040659.9−385922. The all-sky X-ray surveys conducted by the Spectrum Roentgen Gamma (SRG)/extended ROentgen Survey with an Imaging Telescope Array (eROSITA) showed that its X-ray flux increased by a factor of roughly five over six months, and concurrent optical photometric monitoring with the Asteroid Terrestrial-impact Last Alert System (ATLAS) showed a simultaneous increase. Methods. We complemented the eROSITA and ATLAS data by triggering a multiwavelength follow-up monitoring program (X-ray Multi-Mirror Mission: XMM-Newton, Neutron star Interior Composition Explorer: NICER; optical spectroscopy) to study the evolution of the accretion disk, broad-line region, and X-ray corona. During the campaign, X-ray and optical continuum flux subsided over roughly six months. Our campaign includes two XMM-Newton observations, one taken near the peak of this flare and the other taken when the flare had subsided. Results. The soft X-ray excess in both XMM-Newton observations was power law-like (distinctly nonthermal). Using a simple power law, we observed that the photon index of the soft excess varies from a steep value of Γ ∼ 2.7 at the flare peak to a relatively flatter value of Γ ∼ 2.2 as the flare subsided. We successfully modeled the broadband optical/UV/X-ray spectral energy distribution at both the flare peak and post-flare times with the AGNSED model, incorporating thermal disk emission into the optical/UV and warm thermal Comptonization in the soft X-rays. The accretion rate falls by roughly 2.5, and the radius of the hot Comptonizing region increases from the flaring state to the post-flare state. Additionally, from the optical spectral observations, we find that the broad He IIλ4686 emission line fades significantly as the optical/UV/X-ray continuum fades, which could indicate a substantial flare of disk emission above 54 eV. We also observed a redshifted broad component in the Hβ emission line that is present during the high flux state of the source and disappears in subsequent observations. Conclusions. A sudden strong increase in the local accretion rate in this source manifested itself via an increase in accretion disk emission and in thermal Comptonized emission in the soft X-rays, which subsequently faded. The redshifted broad Balmer component could be associated with a transient kinematic component distinct from that comprising the rest of the broad-line region.

MORPHOLOGICAL AND OPTICAL PROPERTIES OF ZNO NANORODS GROWN ONTO SILICON SUBSTRATES: THE IMPACT OF GROWTH TEMPERATURE

ZnO nanorods (NRs) have been successfully grown onto Silicon (Si) substrates. The properties of ZnO NRs have been characterized using field emission scanning microscopy, Photoluminescence, and X-ray diffraction. Results showed that the growth temperature (85, 90, 95, and 100oC) significantly affected the properties of ZnO NRs. At a temperature of 95oC, the structural and optical properties have been significantly enhanced, besides, well-aligned ZnO NRs have been obtained. With the rise of growth temperature from 85 to 95oC, the crystallite size increases (52 to 94 nm), and the near band edge emission to deep level emission ratio is enhanced. Besides, the aspect ratio for the prepared ZnO NRs has increased significantly reaching 19.42. This study emphasizes the significance of growth temperature in tunning the structural and microstructural and subsequently the physicochemical properties of ZnO NRs by fine control of the growth temperature. Moreover, a facile and cost-efficient method for fabricating ZnO nanorods for electronic applications based on silicon is presented in this study.

Evidence for a shock-compressed magnetic field in the northwestern rim of Vela Jr. from X-ray polarimetry

Synchrotron X-ray emission has been detected from nearly a dozen young supernova remnants (SNRs). X-rays of synchrotron origin exhibit linear polarization in a regular, non-randomly oriented magnetic field. The significant polarized X-ray emission from four such SNRs has already been reported on the basis of observations with the Imaging X-ray Polarimetry Explorer (IXPE). The magnetic-field structure as derived from IXPE observations is radial for Cassiopeia A, Tycho's SNR, and SN 1006, and tangential for RX J1713.7-3946. The latter together with the recent detection of a tangential magnetic field in SNR 1E 0102.2-7219 by the Australia Telescope Compact Array in the radio band shows that tangential magnetic fields can also be present in young SNRs. Thus, the dichotomy in polarization between young and middle-aged SNRs (radial magnetic fields in young SNRs, but tangential magnetic fields in middle-aged SNRs), previously noticed in the radio band, deserves additional attention. The present analysis of IXPE observations determines, for the first time, a magnetic-field structure in the northwestern rim of Vela Jr, also known as RX J0852.0$-$4622, and provides a new example of a young SNR with a tangential magnetic field.

Spectroscopic Signature of Metal-hydroxo and Peroxo Species in K-edge X-ray Absorption Spectra.

Metal-dioxygen species are important intermediates formed during dioxygen activations by metalloenzymes in various biological processes, by catalysts in fuel cells, and prior to O2 evolution by photosystem II. In this work, we focus on manganese-porphyrin complexes using tetramesitylporphyrin ligand (TMP) to explore changes in Mn K-edge X-ray absorption spectroscopy (XAS) associated with the formation of Mn-hydroxide and Mn-O2 peroxide species. With limited spectroscopic characterization of these compounds, Mn Kβ X-ray emission spectroscopy (XES), XAS, density functional theory (DFT), and time-dependent DFT (TD-DFT) analysis will enhance our understanding of their complex electronic structure. We show that the shape of the pre-edge in the K-edge Mn X-ray absorption near-edge structure (XANES) can serve as a spectroscopic signature of the MnIII-peroxo formation and thus can be used to track the presence of the side-on peroxide as an intermediate in time-resolved or in situ experiments. Our results will help to further summarize the spectroscopic fingerprints for peroxo and hydroxo species, addressing the challenge of identifying the reactive metal species in catalytic reactions.

Evolution of Tidal Disruption Event Disks with Magnetically Driven Winds

We present a time-dependent, one-dimensional, magnetically driven disk wind model based on magnetohydrodynamic (MHD) equations, in the context of tidal disruption events (TDEs). We assume that the disk is geometrically thin, is gas pressure dominated, and explicitly accounts for magnetic braking and turbulent viscosity through an extended α-viscosity prescription. We find a particular wind solution for a set of basic equations that satisfies the necessary and sufficient conditions for vertically unbound MHD flows. The solution shows that the disk evolves with mass loss due to wind and accretion from the initial Gaussian density distribution. We confirm that the mass accretion rate follows the power law of time t −19/16 at late times in the absence of wind, which matches the classical solution of J. K. Cannizzo et al. We find that the mass accretion rate is steeper than the t −19/16 curve when the wind is present. Mass accretion is also induced by magnetic braking, known as the wind-driven accretion mechanism, which results in a faster decay with time of both the mass accretion and mass-loss rates. In the disk emission, the ultraviolet (UV) luminosity is the highest among the optical, UV, and X-ray luminosities. While the optical and X-ray emission is observationally insignificant without magnetic braking, the X-ray emission is brighter at late times, especially in the presence of magnetic braking. This provides a possible explanation for observed delayed X-ray flares. Our model predicts that late-time bolometric light curves steeper than t −19/16 in UV-bright TDEs are potentially compelling indicators of magnetically driven winds.

Angular anisotropy of hard x rays produced by laboratory atmospheric discharges

The temporal, spectral, and angular characteristics of the x-ray emissions (photons with energies within 5–1000 keV) are exhaustively investigated during the discharge formation at voltages up to 1 MV in approximately 55 cm air gaps. The temporal correlations between the x-ray emissions and discharge voltage and current waveforms are established. The evolution of the discharge plasma structures developing in the time periods of the x-ray generation is traced with a nanosecond resolution. Based on statistical data, theoretical analysis, and estimates the regularities in the x-ray emission characteristics are revealed together with their relationship with the ionization processes occurring in the gas-discharge medium. On the basis of the obtained experimental data, the probable x-ray generation mechanisms are discussed. The findings can provide a deeper understanding of the physics behind the sources of hard x rays arising during the development of laboratory and atmospheric discharges.

Outflow from the very massive Wolf-Rayet binary Melnick 34

Melnick 34 (Mk\,34) is one of the most massive binary systems known and is one of the brightest X-ray point sources in the 30 Doradus region. We investigated the impact of this massive system on the surrounding interstellar medium (ISM) using the optical spectroscopic capabilities of the narrow-field mode (NFM) of the Multi-Unit Spectroscopic Explorer (MUSE). MUSE-NFM spatially resolved the ISM in the vicinity of Mk\,34 with a resolution comparable to that of the HST. The analysis of the N ii \,lambda \,6583 and S ii \,lambda \,6717 emission lines reveals a cone-like structure apparently originating from Mk\,34 and extending southeast. Electron density maps and radial velocity measurements of the ISM lines further support an outflow scenario traced by these emissions. While no clear northwestern counterpart to this outflow was observed, we note increased extinction in that direction, towards the R136 cluster. The ISM material along the projected diagonal of the outflow on both sides of Mk\,34 shows similar properties in terms of the emission line ratios seen in the Baldwin-Phillips-Terlevich diagram. These results are consistent across two observational epochs. Additionally, we examined the residual maps within a 0.5" radius of Mk\,34 after modeling and subtracting the point spread function. The observed variations in the residuals could potentially be linked to Mk\,34's known periodic behavior. However, further observations with appropriate cadence are needed to fully monitor the 155\,day periodicity of Mk\,34's X-ray emissions.

X-ray observations of Blueberry galaxies

Context. Compact star-forming galaxies were dominant galaxy types in the early Universe. Blueberry galaxies (BBs) represent their local analogues, being very compact and having intense star formation. Aims. Motivated by high X-ray emission recently found in other analogical dwarf galaxies, called Green Peas, we probed the X-ray properties of BBs to determine if their X-ray emission is consistent with the empirical laws for star-forming galaxies. Methods. We performed the first X-ray observations of a small sample of BBs with the XMM-Newton satellite. Spectral analysis for detected sources and upper limits measured via Bayesian-based analysis for very low-count measurements were used to determine the X-ray properties of our galaxy sample. Results. Clear detection was obtained for only two sources, with one source exhibiting an enhanced X-ray luminosity to the scaling relations. For the remaining five sources, only an upper limit was constrained, suggesting BBs to be rather underluminous as a whole. Our analysis shows that the large scatter cannot be easily explained by the stochasticity effects. While the bright source is above (and inconsistent with) the expected distribution at almost the 99% confidence level, the upper limits of the two sources are below the expected distribution. Conclusions. These results indicate that the empirical relations between the star formation rate, metallicity, and X-ray luminosity might not hold for BBs with uniquely high specific star formation rates. One possible explanation could be that the BBs may not be old enough to have a significant X-ray binary population. The high luminosity of the only bright source can then be caused by an additional X-ray source, such as a hidden active galactic nucleus or more extreme ultraluminous X-ray sources.

Multi-wavelength observations of the luminous fast blue optical transient AT2023fhn. Up to ∼200 days post-explosion

Luminous fast blue optical transients (LFBOTs) are a class of extragalactic transients notable for their rapid rise and fade times, blue colour, and accompanying luminous X-ray and radio emission. Only a handful have been studied in detail since the prototypical example AT\,2018cow. Their origins are currently unknown, but ongoing observations of previous and new events are placing ever stronger constraints on their progenitors. We aim to put further constraints on the LFBOT AT\,2023fhn, and LFBOTs as a class, using information from the multi-wavelength transient light curve, its host galaxy, and local environment. Our primary results were obtained by fitting galaxy models to the spectral energy distribution of AT\,2023fhn's host and local environment, and by modelling the radio light curve of AT\,2023fhn as due to synchrotron self-absorbed emission from an expanding blast wave in the circumstellar medium. We find that neither the host galaxy nor circumstellar environment of AT\,2023fhn are unusual compared with previous LFBOTs, but that AT\,2023fhn has a much lower X-ray to ultraviolet luminosity ratio than previous events. We argue that the variety in ultraviolet-optical to X-ray luminosity ratios among LFBOTs is likely due to viewing angle differences, and that the diffuse, yet young local environment of AT\,2023fhn - combined with a similar circumstellar medium to previous events - favours a progenitor system containing a massive star with strong winds. Plausible progenitor models in this interpretation therefore include the mergers of black holes and Wolf-Rayet stars or failed supernovae.

Tracing the origin of raw materials used for the production of ancient ceramics: a case study of multi-period archaeological sites in the Turopolje area (Continental Croatia)

The selection of raw materials for ancient pottery production was influenced by a variety of technological and cultural factors, underscoring the importance of characterising these materials to understand the technology of ancient societies. This research examines ancient ceramics from two multi-period archaeological sites: Staro Čiče-Gradišće (Neolithic, Copper Age, Copper/Early Bronze Age, Early Bronze Age, Late Bronze Age, Roman period, and Late Mediaeval period) and Kurilovec-Belinščica (Early Bronze Age and Middle/Late Bronze Age), alongside potential clayey raw materials collected near these settlements. Using a multi-analytical approach (optical microscopy, X-ray powder diffraction, mass and emission spectrometry, and laser granulometry), the research aims to determine the characteristics of the paste recipes (raw clay and tempers) and to examine the type and provenience of the raw materials used for ancient pottery production over different periods of the past (from the Neolithic to the Late Mediaeval period). The results showed that ancient potters preferred to use moderately plastic, sandy clay, while Bronze Age potters often used highly plastic clay. Potters utilised various non-plastic tempering materials, such as sands and gravels, grog, and mollusc shells, with their choice being influenced by the need to enhance technological properties as well as by regional and culturally determined pottery traditions. Most of the ceramics are of local origin, made from easily available raw materials that represent flood sediments of the nearby Sava River. However, non-local materials were detected in Neolithic samples, indicating the presence of exchange networks among those communities.

The impact of proton ion irradiation on Se70Te20In10 thin films: Linear and non-linear optical properties for photonic applications

The examination of the linear and non-linear optical features was conducted on amorphous ternary Se70Te20 In10 thin films, which were exposed to proton irradiation energy of 3 MeV at varying fluences of 5×1013, 5×1014, 5×1015 and 5×1016 ions/cm2. The bulk sample was produced using the melt quenching method, and subsequently, thin films were obtained through electron beam evaporation. Calculations of linear and non-linear optical parameters were carried out based on transmittance and reflectance data acquired from UV–Vis–NIR spectroscopy spanning 300–2500 nm. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) confirmed an amorphous phase in the films. The optical parameters showed strong dependency on the proton radiation fluence. In addition, the existence of minima or maxima for a number of parameters at a fluence of 5×1014 ions/cm2 showed that this was the optimum fluence. The linear and non-linear properties showed that the sample have potential applications in photonic devices.

Enhancing X-ray generation from twisted multilayer van der Waals materials by shaping electron wavepackets

We study twisted bilayer van der Waals (vdW) materials as a platform to generate versatile bremsstrahlung X-rays, and show that the twist angle in bilayer vdW materials provides an unprecedented degree of controllability over various properties of bremsstrahlung radiation from these materials. Specifically, we combine the waveshaping of the free electron’s quantum wavepacket with the unique crystalline atomic positioning of twisted bilayers to realize shaped bremsstrahlung X-rays, which feature enhancements in directionality and intensity. In the process, we present a theoretical model for bremsstrahlung radiation that is applicable to twisted multilayer vdW materials in general. We also investigate the dependence of our X-ray emission mechanism on physical parameters, including the interlayer spacing and number of layers. Our findings pave the way for the use of twisted multilayer van der Waals materials in the generation of tailored X-ray spectra for applications like X-ray imaging, X-ray fluorescence, and X-ray treatment.

Joining the dots: high redshift black holes

ABSTRACT A recent paper suggested that emission from the central supermassive black holes in high-redshift galaxies must be tightly collimated by the effects of partly expelling a super-Eddington mass supply. I show here that this idea predicts that these galaxies should produce very little detectable rest-frame X-ray emission, appear Compton thick, and show no easily detectable sign of outflows. All of these properties agree with current observations. To produce these effects, the mass supply to the black holes should exceed the Eddington rate by factors ${\sim} 50{\!-\!}100$, which appears in line with conditions during the early growth of the holes. I note that theoretical derivations of the ratio of black hole mass to host galaxy stellar mass already predict that this should increase significantly at high redshift, in line with recent observations.

Structure-Function Correlation in Cobalt-Induced Brain Toxicity.

Cobalt toxicity is difficult to detect and therefore often underdiagnosed. The aim of this study was to explore the pathophysiology of cobalt-induced oxidative stress in the brain and its impact on structure and function. Thirty-five wild-type C57B16 mice received intraperitoneal cobalt chloride injections: a single high dose with evaluations at 24, 48, and 72 h (n = 5, each) or daily low doses for 28 (n = 5) or 56 days (n = 15). A part of the 56-day group also received minocycline (n = 5), while 10 mice served as controls. Behavioral changes were evaluated, and cobalt levels in tissues were measured with particle-induced X-ray emission. Brain sections underwent magnetic resonance imaging (MRI), electron microscopy, and histological, immunohistochemical, and molecular analyses. High-dose cobalt caused transient illness, whereas chronic daily low-dose administration led to long-term elevations in cobalt levels accompanied by brain inflammation. Significant neurodegeneration was evidenced by demyelination, increased blood-brain barrier permeability, and mitochondrial dysfunction. Treated mice exhibited extended latency periods in the Morris water maze test and heightened anxiety in the open field test. Minocycline partially mitigated brain injury. The observed signs of neurodegeneration were dose- and time-dependent. The neurotoxicity after acute exposure was reversible, but the neurological and functional changes following chronic cobalt administration were not.

Fast and Robust Noise Background Modeling and Quasiperiodic Oscillation Detection for Astronomical Time Series

Spectrum with confidence levels is a commonly used method for quasiperiodic oscillation (QPO) detection, but it is prone to yield false positives for two reasons: poor choice and/or biased modeling of the null hypothesis (or noise background). Motivated by this, we propose a new time-domain maximum-likelihood estimation method, which can quickly and accurately estimate the noise background free from background trends, spectra peaks, and even QPOs. Our method provides a wide range of candidate stochastic models (e.g., conventional first-order autoregressive, power law, generalized Gauss–Markov, Matérn, and damped random walk), some of which have not been considered previously. Some pitfalls (e.g., detrending) in previous QPO detections are also correctly processed to minimize the false detections. Along with the multitaper method and wavelet, we revisit QPO detection in the X-ray emission from the active galaxies RE J10341+396 and 1H 0707-495, and point out why the significance levels of the QPO at ∼2.6 × 10−4 Hz would be different in previous detections and reduced if the whole observation duration is considered. Our algorithm can be easily extended to other branches of astrophysics and beyond.

Ion Beam-Induced Luminescence (IBIL) for Studying Manufacturing Conditions in Ceramics: An Application to Ceramic Body Tiles.

The first experimental results obtained by the ion beam-induced luminescence technique from the ceramic bodies of ancient tiles are reported in this work. The photon emission from the ceramic bodies is related to the starting minerals and the manufacturing conditions, particularly the firing temperature and cooling processes. Moreover, the results indicate that this non-destructive technique, performed under a helium-rich atmosphere instead of an in-vacuum setup and with acquisition times of only a few seconds, presents a promising alternative to traditional, often destructive, compositional characterisation methods. Additionally, by adding other ion beam-based techniques such as PIXE (Particle-Induced X-ray Emission) and PIGE (Particle-Induced Gamma-ray Emission), compositional information from light elements such as Na can also be inferred, helping to also identify the raw materials used.

Anisotropic electronic structure study of MgB2C2 using soft X-ray emission 0spectroscopy microscopes.

The anisotropic electronic structure of MgB2C2 was studied using soft X-ray emission spectroscopy electron microscopes. MgB2C2 fragments were selected by examining C K-emission profiles. C and B K-emission and Mg L-emission spectra were obtained, revealing common and distinct structures that reflect the mixing of valence orbitals. Since the material is reported to have two-dimensional B-C honeycomb layers, the orientational dependence of these emission spectra was also examined. Experimental data were compared with theoretically calculated partial density of states of the valence bands of the material. The C K-emission profile showed an apparent orientational dependence, while the B K-emission exhibited minimal dependence. This difference originated from the different energy distributions of C-2pz and B-2pz components in the valence bands. The Mg L-emission intensity was very small, likely due to charge transfer from Mg atoms to B-N layers. The Mg L-emission profile showed a peak related to structures in C-K and B-K. An unexpected intensity was observed just above the valence bands, which also showed orientational dependence, possibly due to a small deviation from the ideal composition of Mg:B:C = 1:2:2.