Current Issue : July-September Volume : 2025 Issue Number : 3 Articles : 6 Articles
V902 Mon is one of a few eclipsing intermediate polars (IPs) and shows deep eclipses in the optical lightcurves. The presence of a strong Fe Kα fluorescence line in its X-ray spectrum and its low X-ray flux compared to other IPs suggests significant absorption, most likely from an accretion disk. In an observation carried out using the Nuclear Spectroscopic Telescope Array (NuSTAR), we confirm the presence of an X-ray eclipse in the energyresolved lightcurves, coincident with the optical AAVSO/CV-band lightcurves. Broadband X-ray spectral analysis using NuSTAR and XMM-Newton observations confirm a strong absorption NH ∼ 1023 cm−2 local to the source, along with a high equivalent width of about 0.7 keV for an Fe Kα fluorescence line. We interpret this using a model similar to an accretion disk corona source, which has a very high inclination, and the compact object is heavily obscured by the body of the accretion disk. We propose that the primary X-rays from the accretion column in V902 Mon are hidden from our direct view at all times by the accretion disk. In this scenario, the observed scattered X-rays indicate substantial absorption of direct X-rays by the accretion disk. Additionally, a strong Fe fluorescence line suggests reprocessing of the radiation by a more extended region, such as the pre-shock region, which could be located a few white dwarf radii above the orbital plane....
This study investigates the chemical and mineralogical composition of bauxite samples from five operating sites in Boffa, Guinea, aiming to assess their quality and suitability for alumina production using the Bayer process. The researchers employed X-ray fluorescence (XRF) to determine elemental composition after calcination and fusion with lithium borates. The results indicate that the Boffa bauxites are high in alumina (34.28% - 54.02% Al2O3) and low in silica (0.98% - 7.29% SiO2), suggesting high quality and economic viability....
Several studies over the last two decades have used canonical correlation analysis (CCA) to study the relationships between main γ-ray (e.g. fluence, peak flux, and duration) and main X-ray (flux, decay and spectral index, and hydrogen column density) data from gamma-ray bursts (GRBs). In this paper, we revisit this approach using a much larger dataset to identify potential new insights into these relationships. We used CCA to investigate the interrelationship of the aforementioned gamma-ray and X-ray parameters. Using the derived canonical variables, we calculated their correlations (canonical loadings) with the original data. Consistently with previous research, the analysis revealed that gamma-ray fluence and X-ray flux have the strongest correlation, while the X-ray decay index and spectral index have a lower contribution. Interestingly, our analysis of a much larger dataset reveals that the HI column density makes a significant contribution to the overall correlation. This finding, in the context of the collapsar model for long GRBs, could be interpreted as an indication that the progenitor star ejected an HI envelope during the GRB....
The advent of X-ray Free Electron Lasers (XFELs) has opened unprecedented opportunities for advances in the physical, chemical, and biological sciences. With their state-of-the-art methodologies and ultrashort, and intense X-ray pulses, XFELs propel X-ray science into a new era, surpassing the capabilities of traditional light sources. Ultrafast X-ray scattering and imaging techniques leverage the coherence of these intense pulses to capture nanoscale structural dynamics with femtosecond spatial-temporal resolution. However, spatial and temporal resolutions remain limited by factors such as intrinsic fluctuations and jitters in the Self-Amplified Spontaneous Emission (SASE) mode, relatively low coherent scattering cross-sections, the need for high-performance, singlephoton- sensitive detectors, effective sample delivery techniques, low parasitic X-ray instrumentation, and reliable data analysis methods. Furthermore, the highthroughput data flow from high-repetition rate XFEL facilities presents significant challenges. Therefore, more investigation is required to determine how Artificial Intelligence (AI) can support data science in this situation. In recent years, deep learning has made significant strides across various scientific disciplines. To illustrate its direct influence on ultrafast X-ray science, this article provides a comprehensive overview of deep learning applications in ultrafast X-ray scattering and imaging, covering both theoretical foundations and practical applications. It also discusses the current status, limitations, and future prospects, with an emphasis on its potential to drive advancements in fourthgeneration synchrotron radiation, ultrafast electron diffraction, and attosecond X-ray studies....
X-ray response performances of a p-NiO/β-Ga2O3 hetero-junction diode (HJD) X-ray detector were studied before and after γ-ray irradiation at −200 V, with a total dose of 13.5 kGy(Si). The response performances of the HJD X-ray detector were influenced by the trap-assistant conductive process of the HJD under reverse bias, which exhibited an increasing net (response) current, nonlinearity, and a long response time. After irradiation, the Poole–Frenkel emission (PFE) dominated the leakage current of HJDs due to the higher electric field caused by the increased net carrier concentration of β-Ga2O3. This conductive process weakened the performance of the HJD X-ray detector in terms of sensitivity, output linearity, and response speed. This study provided valuable insights into the radiation damage and performance degradation mechanisms of Ga2O3-based radiation detectors and offered guidance on improving the reliability and stability of these radiation detectors....
About 100 sherds from Haltern 70 amphorae recovered from Castro do Vieito (NW Portugal) and from kiln sites located at Guadalquivir valley, Rio Tinto valley, bay of Cadix and Algarve coast, were analyzed by X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The study aimed mainly to verify the provenance of Castro do Vieito (CV) Haltern 70 amphorae. Principal components analysis (PCA) and cluster analysis (CA) were performed. A CV sherd with a potter’s stamp “LH…” was studied among other CV sherds and it was found that they have the same origin, and probably a unique provenance. The most considered area of Haltern 70 type, Guadalquivir valley, is not likely to be the origin of CV Haltern 70 amphorae. Moreover, it is quite possible that these amphorae were produced in a region with Nb rich soils....
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