Search Results (160)

PSR B1259-63/LS 2883 is a well-studied gamma-ray binary hosting a pulsar in a 3.4-year eccentric orbit around a Be-type star. Its non-thermal emission spans from radio to TeV energies, exhibiting a significant increase near the periastron passage. This paper is dedicated to the analysis of INTEGRAL observations of the system following its last periastron passage in June 2024. We aim to study the spectral evolution of this gamma-ray binary in the soft (0.3–10 keV) and hard (30–300 keV) X-ray energy bands. We performed a joint analysis of the data taken by INTEGRAL/ISGRI in July–August 2024 and quasi-simultaneous Swift/XRT observations. The spectrum of the system in the 0.3–300 keV band is well described by an absorbed power law with a photon index of $\Gamma =1.42\pm 0.03$. We place constraints on potential spectral curvature, limiting the break energy $E_{\mathrm{b}}>30$ keV for $\Delta \Gamma >0.3$ and cutoff energy $E_{\mathrm{cutoff}}>150$ keV at a 95% confidence level. For one-zone leptonic emission models, these values correspond to electron distribution spectral parameters of $E_{\mathrm{b},\mathrm{e}}>0.8$ TeV and $E_{\mathrm{cutoff},\mathrm{e}}>1.7$ TeV, consistent with previous constraints derived by H.E.S.S. Full article

Supernova 2023ixf occurred on 18 May 2023 in the nearby galaxy Messier 101 ($D\approx 6.85$ Mpc), making it the closest supernova in the last decade. Following its discovery, astronomers around the world rushed to observe the explosion across the electromagnetic spectrum in order to uncover its early-time properties. Based on multi-wavelength analysis during its first year after explosion, Supernova 2023ixf is a type II supernova that interacted with dense, confined circumstellar material in its local environment—this material being lost from its red supergiant progenitor in the final years before explosion. In this article, we will review the findings of >80 studies already published on this incredible event and explore how the synthesis of SN 2023ixf observations across the electromagnetic spectrum can be used to constrain type II supernova explosion physics in addition to the uncertain mass loss histories of red supergiant stars in their final years. Full article

A series of 11 Byzantine gold coins were investigated, including two examples of an extremely rare type called histamenon “stellatus”, from around the reign of the Byzantine emperor Constantine IX Monomachos (AD 1042–1055). The methods applied were X-ray fluorescence spectroscopy (XRF), specific density measurement (SD), and scanning electron microscopy (SEM). The debasement (decreasing gold content) of the Byzantine nomisma gold coinage during the 11th century was demonstrated. A method combining XRF and SD measurement combined with a graphical presentation/analysis called a ternary plot was also demonstrated. The measured gold content of the 11 coins was corrected for the possible “outwashing” effect and a potential cleaning of ancient gold. A model for the estimation of the gold content of Byzantine histamenon nomisma gold coins from the period AD 1020–1118, based on the specific density (SD), was derived. It was demonstrated that two analyzed histamenon “stellati” coins likely were minted around AD 1054–1055, possibly during the same period as the occurrence of the supernova SN1054, known as the Crab-nebula. It is further discussed if the gold content and size of the stars shown on those coins can be correlated to the visibility of the supernova from June AD 1054 to January AD 1055. Full article

Natrium superionic conductor (NASICON) compounds have emerged as a rising star in the field of sodium-ion batteries (SIBs) owing to their stable framework structure and high Na⁺ ionic conductivity. The NASICON-structured Na₂VTi(PO₄)₃ manifests significant potential as Na⁺ storage material, characterized by decent rate capability and cyclability. However, the low redox potential of Ti³⁺/Ti⁴⁺ and undesirable energy density limit its practical applications. We developed a NASICON-structured Na₃Co_2/3V_2/3Ti_2/3(PO₄)₃ (NCTVP) cathode material by doping an appropriate amount of cobalt into Na₂VTi(PO₄)₃. Cobalt doping introduces a Co³⁺/Co²⁺ redox couple at ~4.1 V and activates the V⁵⁺/V⁴⁺ redox at ~3.9 V, resulting in significantly increased medium discharge voltage and capacity. NCTVP demonstrates a high capacity of over 160 mAh g⁻¹ at 20 mA g⁻¹. With a medium discharge voltage of ~2.7 V, the energy density of NCTVP reaches 432.0 Wh kg⁻¹. NCTVP also demonstrates desirable cycling stability (87.4% retention for 100 cycles at 50 mA g⁻¹). In situ X-ray diffraction discloses a solid solution reaction mechanism for NCTVP, while the galvanostatic intermittent titration technique demonstrates fast Na⁺ diffusion kinetics. NCTVP also demonstrates high capacity and good cyclability in full cells. This contribution demonstrates an effective approach for the construction of NASICON materials for SIBs. Full article

MWC 342 (V1972 Cyg) was discovered nearly 90 years ago as an early-type emission-line star. It was among the first hot stars whose strong infrared excess was detected in the early 1970s. Several mostly short-term photometric and spectroscopic studies resulted in contradictory conclusions about the nature and evolutionary status of MWC 342. It has been classified as a pre-main-sequence Herbig Be star, an evolved suspected binary system, and a long-period variable star. Suggestions on the nature of the secondary component to this B0/B1 primary included a cool M-type giant and an X-ray source. We collected medium- and high-resolution optical spectra of MWC 342 taken in 1994–2024 as well as optical photometric data taken in 1986–2024. Analysis of these data shows strong variations in the object’s brightness and spectral line properties at various time scales, but no strictly periodic phenomena have been found. Inparticular, such a long-term dataset allowed us to reveal the optical brightness variations over a nearly 20-year-long quasi-period, as well as their anti-correlation with the H$\alpha$ emission-line strength. Also, we did not confirm the presence of He ii emission lines and absorption lines of the star’s atmosphere that were suspected in previously published studies. Full article

We summarize the X-ray emission from young SNe. Having accumulated data on most observed X-ray SNe, we display the X-ray lightcurves of young SNe. We also explore the X-ray spectra of various SN types. The X-ray emission from Type Ib/c SNe is non-thermal. It is also likely that the emission from Type IIP SNe with low mass-loss rates (around 10⁻⁷ M_⊙ yr⁻¹) is non-thermal. As the mass-loss rate increases, thermal emission begins to dominate. Type IIn SNe have the highest X-ray luminosities, and are clearly thermal. We do not find evidence of non-thermal emission from Type IIb SNe. The aggregated data are used to obtain approximate mass-loss rates of the progenitor stars of these SNe. Type IIP have progenitors with mass-loss rates $<{10}^{-5}{\mathrm{M}}_{\odot }$ yr⁻¹, while Type IIn progenitors generally have mass-loss rates $>{10}^{-3}{\mathrm{M}}_{\odot }$ yr⁻¹. However, we emphasize that the density of the ambient medium is the important parameter, and if it is due to a non-steady outflow solution, it cannot be translated into a mass-loss rate. Full article

Background/Objectives: Polymeric nanofibers are promising platforms for skin treatment applications due to their large surface area and high porosity, which promote enhanced drug delivery. This study aimed to develop and compare poly(lactic acid)-based (PLA) nanofibrous mats, using linear PLA and a star-like PLA-pentaerythritol (PLA-PE) copolymer, as carriers for transdermal delivery of the antibacterial agent levofloxacin (LEV). Methods: Electrospinning was employed to fabricate nanofibers from PLA and PLA-PE solutions. Spinning parameters and polymer concentrations (10% w/v PLA and 20% w/v PLA-PE) were optimized to produce uniform fibers. LEV was loaded at 10% and 20% w/w. A sum of complementary characterization techniques, including scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), were applied to comparatively investigate the fibers’ morphology, structural properties, and crystallinity. Drug loading, porosity, degradation, and in vitro release profiles were evaluated. Results: PLA-PE nanofibers demonstrated smaller diameters and higher porosity (up to 90.1%) compared to PLA (82.4%), leading to enhanced drug loading (up to 34.78%) and faster degradation (55% vs. 43% mass loss over 60 days). Drug release exhibited a biphasic profile with an initial burst followed by sustained release. PLA-PE formulations released up to 60.2% LEV, compared to 38.1% for PLA counterparts. Conclusions: The star-like PLA-PE copolymer enhances nanofiber properties relevant to the desired application, including porosity, degradation rate, and drug release. These findings suggest that PLA-PE is a promising material for developing advanced transdermal antibiotic delivery systems. Full article

The interpretation of the thermal relaxation of some transiently accreting neutron stars in quasipersistent soft X-ray transients, especially MXB 1659-29, has been found to be challenging within the traditional deep crustal heating paradigm. Due to the pinning of quantized vortices, the neutron superfluid is not expected to remain at rest in the crust, as was generally assumed. We have recently shown that for sufficiently large relative superflows, the neutron superfluid could become gapless. This dynamical phase could naturally explain the late-time cooling of MXB 1659-29. However, the interpretation of the last observation of MXB 1659-29 in 2013 before its second accretion phase in 2015 remains debated, with some spectral fits being consistent with no further temperature decline. Here, we revisit the cooling of this neutron star considering the different fits. New simulations of the crust cooling are performed, accounting for neutron diffusion and allowing for gapless superfluidity. In all cases, gapless superfluidity is found to provide the best fit to observations. Full article

The process of mass exchange between the components of High-Mass X-ray Binary (HMXB) systems with neutron stars undergoing wind-fed accretion is discussed. The X-ray luminosity of these systems allows us to evaluate the mass capture rate by the neutron star from the stellar wind of its massive companion and set limits on the relative velocity between the neutron star and the wind. We found that the upper limit to the wind velocity in the orbital plane during the high state of the X-ray source is in the range of 120–1000 $\mathrm{km}{\mathrm{s}}^{-1}$, which is by a factor of 2–4 lower than both the terminal wind velocity and the speed of the wind flowing out from the polar regions of massive stars for all the objects under investigation. This finding is valid not only for the systems with Be stars, but also for the systems in which the optical components do not exhibit the Be phenomenon. We also show that the lower limit to the radial wind velocity in these systems can unlikely be smaller than a few percent of the orbital velocity of the neutron star. This provides us with a new constraint on the mass transfer process in the outflowing disks of Be-type stars. Full article

The broad point spread function of the NuSTAR telescope makes resolving astronomical X-ray sources a challenging task, especially for off-axis observations. This limitation has affected the observations of the high-mass X-ray binary pulsars SXP 15.3 and SXP 305, in which pulsations are detected from nearly overlapping regions without spatially resolving these X-ray sources. To address this issue, we introduce a deconvolution algorithm designed to enhance NuSTAR’s spatial resolution for closely spaced X-ray sources. We apply this technique to archival data and simulations of synthetic point sources placed at varying separations and locations, testing the algorithm’s efficacy in source detection and differentiation. Our study confirms that on some occasions when SXP 305 is brighter, SXP 15.3 is also resolved, suggesting that some prior non-detections may have resulted from imaging limitations. This deconvolution technique represents a proof of concept test for analyzing crowded fields in the sky with closely spaced X-ray sources in future NuSTAR observations. Full article

Accreting white dwarf binaries (AWDs) comprise cataclysmic variables (CVs), symbiotics, AM CVns, and other related systems that host a primary white dwarf (WD) accreting from a main sequence or evolved companion star. AWDs are a product of close binary evolution; thus, they are important for understanding the evolution and population of X-ray binaries in the Milky Way and other galaxies. AWDs are essential for studying astrophysical plasmas under different conditions along with accretion physics and processes, transient events, matter ejection and outflows, compact binary evolution, mergers, angular momentum loss mechanisms, and nuclear processes leading to explosions. AWDs are also closely related to other objects in the late stages of stellar evolution, with other accreting objects in compact binaries, and even share common phenomena with young stellar objects, active galactic nuclei, quasars, and supernova remnants. As X-ray astronomy came to a climax with the start of the Chandra and XMM-Newton missions owing to their unprecedented instrumentation, new excellent imaging capabilities, good time resolution, and X-ray grating technologies allowed immense advancement in many aspects of astronomy and astrophysics. In this review, we lay out a panorama of developments on the study of AWDs that have been accomplished and have been made possible by these two observatories; we summarize the key observational achievements and the challenges ahead. Full article

We explore the evolutionary link between Galactic Be X-ray binaries (BeXBs) and Galactic field double neutron stars (DNSs) based on the properties of the NS spin period—P and binary orbital period—$P_{\mathrm{orb}}$. First, both BeXB and DNS sources show positive correlation trends in P versus $P_{\mathrm{orb}}$ relation ($P-P_{\mathrm{orb}}$ diagram), which may relate to the influence of the accretion evolution. Secondly, the two types of sources exhibit similar bi-modal P/$P_{\mathrm{orb}}$ distributions with the gaps of $P\sim 40$ s/$P_{\mathrm{orb}}\sim 60$ days for BeXBs and $P\sim 50$ ms/$P_{\mathrm{orb}}\sim 1$ day for DNSs, respectively. We propose a possibility that Galactic BeXBs may transfer the bi-modal P/$P_{\mathrm{orb}}$ classifications to Galactic field DNSs during the evolution process. Furthermore, based on the bi-modal gaps, we infer the contraction factors of P (by $\sim {\displaystyle \frac{1}{800}}$) and $P_{\mathrm{orb}}$ (by $\sim {\displaystyle \frac{1}{60}}$) valuesin the evolution from Galactic BeXBs to Galactic field DNSs. We find that the scaled P or $P_{\mathrm{orb}}$ values of Galactic BeXBs share the similar bi-modal distributions to that of Galactic field DNSs, and these results can offer a reference to trace the classification and evolution between the two types of sources. Full article

The star $\gamma$ Cas and its analogs are a subset of Be stars that display particularly hard and bright thermal X-ray emission, which has no equivalent among other massive stars. Here, I will review their characteristics and present the latest results of our optical and X-ray monitoring campaigns, including an assessment of the links between the circumstellar environment and the high-energy properties. Possible scenarios to explain this phenomenon will be presented in light of these observational results. Full article

The misfolding and amyloid aggregation of proteins have been attracting scientific interest for a few decades, due to their link with several diseases, particularly neurodegenerative diseases. Proteins can assemble and result in insoluble aggregates that, together with intermediate oligomeric species, modify the extracellular environment. Many efforts have been and are devoted to the search for cosolvents and cosolutes able to interfere with amyloid aggregation. In this work, we intensively study the effect of saponins, bioactive compounds, on human insulin aggregation. To monitor the kinetic of amyloid aggregation following secondary structure changes, we perform fluorescence and UV-Visible absorption spectroscopies, using Thioflavin T and Congo Red as amyloid specific probes, and Circular Dichroism. To study the overall structural features and size of aggregates, we perform Synchrotron Small-Angle X-ray Scattering and Dynamic Light Scattering experiments. The morphology of the aggregates was assessed by Atomic Force Microscopy. To deepen the understanding of the saponins interaction with insulin, a Molecular Dynamics investigation is performed, too. The reported data demonstrate that saponins interfere with the amyloid aggregation by inducing a strong inhibition on the formation of insulin fibrils, likely through specific interactions with insulin monomers. A dose-dependent effect is evident, and amyloid inhibition is already clear when saponins are just 0.01% w/w in solution. We suggest that saponins, which are natural metabolites present in a wide range of foods ranging from grains, pulses, and green leaves to sea stars and cucumbers, can be promising metabolites to inhibit human insulin aggregation. This basic research work can pave the way to further investigations concerning insulin amyloidosis, suggesting the use of saponins as amyloid inhibitors and/or stabilizing agents in solution. Full article

Accreting X-ray pulsars, located in X-ray binaries, are neutron stars with magnetic fields as strong as $B\sim {10}^{12–13}$ G. This review offers a concise overview of the accretion and radiation processes of X-ray pulsars and summarizes their rich observational features, particularly focusing on complex and variable temporal phenomena, spectral properties, and evolution, the new window for X-ray polarimetry and multi-wavelength advances. We also briefly discuss other related systems, i.e., gamma-ray binaries and pulsating ultraluminous X-ray sources. Full article