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Pre-formed metal membranes for diaphragm compressors: a combined numerical and experimental investigation of forming process and fatigue life
No full textConventional diaphragm compressors are fundamentally limited by the low displaced volume and poor fatigue life of their flat metal diaphragms. This study presents a comprehensive, numerical and experimental investigation of the design, manufacturing, and performance of pre-formed, bistable dome-shaped membranes to overcome these limitations. A complete process chain was modeled using the finite element method (FE), simulating the hydroforming process, subsequent elastic springback, and the operational folding cycle. The model was based on the characterization of the anisotropic material properties of high-strength stainless steel foil made of 1.4310 in a spring-hard condition. To validate the simulation, prototypes were manufactured via hydroforming and their final geometries were analyzed using an optical 3D scanning system, showing improved results using the anisotropic material model compared the isotropic. X-ray diffraction (XRD) analysis was applied to quantify induced martensite transformation as part of the material hardening behavior. Subsequent, fatigue life testing was performed on the manufactured membranes to assess their durability under cyclic loading. The results demonstrate that the hydroforming process yields a robust component with superior performance. The optimized hydroformed diaphragm successfully endured over 5 million cycles without failure and enabled an increase of 60% in displaced volume compared to a conventional flat membrane. This integrated design and validation methodology provides a clear pathway for developing next-generation, high-performance diaphragm compressors
Epicyclic frequencies around charged regular black hole: constraints using different quasars data
No full textWe examine the dynamics of test particles and epicyclic frequencies around a charged regular black hole, investigating how its mass M and charge q influence orbital motion, stability, and high-energy phenomena. Using an effective potential approach, we derive analytical expressions for the specific energy and angular momentum of particles in stable circular orbits, demonstrating that increasing q shifts the innermost stable circular orbits (ISCOs) inward compared to the Schwarzschild black hole. We compute the radial, vertical, and orbital oscillation frequencies, revealing significant deviations from standard black hole predictions, particularly in the 3:2 frequency ratio associated with high-frequency. Through Markov Chain Monte Carlo (MCMC) analysis of observational data from X-ray binaries (including H 1743-322 and GRS 1915+105), we constrain the charge parameter to –0.4 at high confidence levels. Further, we study particle collisions near the horizon, finding that centre-of-mass energies can be enhanced by up to 40% for , indicating observable signatures in high-energy astrophysical processes. Our results provide testable predictions for distinguishing charged regular black holes from classical singular black holes. This work establishes a framework for probing black hole structures in the strong-gravity regime, with implications for fundamental physics and quantum gravity
Asteroid characterization using Data Release 3 Gaia. II. Taxonomic classification
No full textWe study the taxonomic classification of asteroids observed by as a continuation of the lightcurve inversion work presented in Paper I. Gaia
We examine the taxonomic classification of asteroids by using both Data Release 3 (DR3) photometric and spectroscopic data. Particular focus is placed on Ch-class asteroids, as their potentially hydrated nature makes them promising candidates for sample-return missions and the asteroid mining industry. Gaia
We utilized the photometric slopes and geometric albedos (via absolute magnitudes) derived from lightcurve inversion, and the DR3 spectra (from 418 nm to 770 nm) as classification parameters. We also considered how different parameter sets affect classification accuracies for separate asteroid classes. We classified the asteroids with a combination of linear discriminant analysis and a nearest neighbor classifier. Gaia
We achieve a classification accuracy of 92% for known S-class asteroids and an accuracy of 85% for Ch-class asteroids with a known set of 328 asteroids. Given the three classification parameters, tentative class designations for 1668 previously unclassified asteroids are provided in the Mahlke taxonomy. We also show that the photometric slope values vary significantly within asteroid classes, with a standard deviation three to four times the mean slope uncertainties.
We show that the combination of photometry and spectroscopy can be useful in the taxonomic classification of asteroids observed by . Further studies of the surface roughness at different scales could help clarify the potential of the photometric slope in classification efforts. Gai
Massive dusty multiphase outflow in local merger shows no sign of slowing on kiloparsec scales
No full textWe use ALMA CO(1-0) observations and VLT/MUSE rest-frame optical data of the ultraluminous infrared galaxy (ULIRG) IRAS20100-4156 at z=0.1297 to characterize its powerful outflow in multiple phases using tracers of cold molecular, ionized, and neutral atomic gas and dust as well. Our analysis uses the correspondence with the stellar velocity field to split the complex emission line profiles of the CO(1-0) line into components in gravitational and non-gravitational motion. We find a massive (8 9 molecular outflow containing about 40% of the total molecular gas mass in the system. The outflow shows a bi-conical morphology centered on the brightest galaxy in the merger, oriented along its minor axis and extending to sim5,kpc. This outflow has a characteristic velocity of 170,km/s, an outflow mass rate of 700, a depletion time of 16,Myr, and energetics consistent with star formation as a driver. The neutral atomic and ionized gas phases traced by NaI absorption and Hα emission show counterparts to the blueshifted cold molecular outflow but are only 15% and 3% as massive. None of the three gas phases show any signs of slowing down over the extent at which we detected the outflow, suggesting an acceleration mechanism acting on the outflowing gas at kpc scales. We also detect 3.5 10^7 of dust, traced by optical extinction in the MUSE data, in the blueshifted outflowing cold molecular gas. The ionization state of the non-outflowing gas is consistent with star formation, while the outflowing component shows shock-like ionization. We conclude that the multiphase outflow in IRAS20100-4156 originates in the southeast nucleus of the merger and is driven by the starburst activity there, with radiation pressure likely playing a significant role in its acceleration
Rings around irregular bodies. II. Numerical simulations of the 1/3 spin-orbit resonance confinement and applications to Chariklo
No full textOur goal was to understand how collisional rings can be confined near second-order SORs in spite of the fact that they force self-intersecting streamlines.
We used full 3D numerical simulations that treat rings of inelastically colliding particles orbiting nonaxisymmetric central bodies, characterized by a dimensionless mass anomaly parameter μ. While most of our simulations ignore self-gravity, a few runs include gravitational interactions between particles, providing preliminary results on the effect of self-gravity on the ring confinement.
The 1/3 SOR can confine ring material, by transferring the forced resonant mode into free Lindblad modes. We derived a criterion ensuring that the 1/3 SOR counteracts viscous spreading. It reads k μ^2 ≳ τ R^2, where k is a dimensionless coefficient, τ is the ring optical depth, and R is the particle radius. Expressing R in terms of the radius of the synchronous orbit, we obtain k ∼ 4 for the 1/3 SOR acting on nongravitating rings. Assuming meter-sized ring particles, and τ in Chariklo's case. The confinement is not permanent as a slow outward leakage of particles is observed in our simulations. This leakage can be halted by an outside moonlet with a mass of ∼ 10^ 10^ -5 this requires a threshold value μ ≳ 10^ -3 -7 -10^ -6 relative to Chariklo, corresponding to subkilometer-sized objects. With self-gravity, the ring viscosity increases by a factor of a few in low-τ rings due to gravitational encounters. For large τ, self-gravity wakes enhance the viscosity ν by a factor of ∼100 compared to a nongravitating ring, requiring ∼tenfold larger μ values since the threshold value increases proportionally to sqrtν
Pick-up-generated ion cyclotron waves around Io
No full textIo, the innermost Galilean moon of Jupiter, is the main source of plasma in the Jovian magnetosphere. The neutral gas coming from the moon will get ionized through ultra-violet radiation and electron impacts. The newly created ions then get picked up by the Jovian magnetic field and start gyrating, thereby creating a ring-beam distribution in velocity space. This type of distribution is unstable with respect to the generation of ion cyclotron waves.
The aim of this study is to characterize the escaping gas from Io's atmosphere into the Jovian magnetosphere.
The Galileo magnetometer data have been investigated for the five Io flybys that have magnetometer data available. The ion cyclotron waves can be measured with magnetometers and through spectral analysis the specific pick-up ions can be determined. Assuming that the energy of the ions in the ring-beam distribution is fully transferred to the cyclotron waves, the pick-up ion densities can be estimated for all these species.
We found evidence of sulfur-bearing ions , , , and , as well as either or (which have the same mass-to-charge ratio and cannot be discerned), and for non-sulfur-bearing ions: , , , and . We also present a first plausible detection of Io-genic phosphorous through the detection of cyclotron waves. SO3+ SO2+ SO+ S+ H2S+ ^ 34 S+ ^ 35 Cl+ ^ 37 Cl+ K+ Si+ P+
The main pick-up densities are related to and , varying with distance from Io between ∼ 10^8 and ∼ 10^6 m SO2+ SO+ -3 , with the other ions exhibiting a similar variation, but their pick-up densities are lower by an order of magnitude
Young system development in a cometary globule: An investigation into the eccentric disk around AT Pyx⋆ in terms of planet formation and interaction with its surrounding environment
No full textTo understand the formation of planetary systems, it is necessary to observe and study systems at different evolutionary stages and in different environments. This paper presents new data and analyses of the AT Pyx system, a disk-hosting young star located in a cometary globule in the Gum Nebula. This radiation-driven structure is an unusual environment for observations of planet formation, and differs greatly from the low-mass star-forming regions disks are most commonly observed in.
Aided by a collection of visual and spectroscopic data available for this system, our aim is to infer the possibility of embedded planets existing within the disk and how the system's environment may affect its disk morphology.
Using data from the VLT's instruments XSHOOTER, ESPRESSO, and most prominently SPHERE, along with data from ALMA, we made a variety of measurements (geometric, photometric, and otherwise) to characterise the observed disk features and attributes such as spiral arms and eccentricity. Mapping of the velocity components was also undertaken using the ALMA gas line data to characterise disk orientation and determine the likelihood that the system is experiencing a late-stage infall event.
The disk is measured to have a position angle of 28.06pm0.02 ̧irc and an inclination of 42.5pm0.5^̧irc. The disk is found to be eccentric with measured e when deprojected. Under the assumption that the formation of a planet is wholly responsible for the primary and secondary spiral arms, we find the mass of such a planet can range between 0.004 and 3 Jupiter masses. Measurements of the velocities associated with nearby globule cloud material return reasonable velocities for a late-stage infall event. We estimate the far-ultraviolet (FUV) field strength at AT Pyx's location to be low in comparison to other surveyed disks. We also find that AT Pyx is possibly a binary system.
AT Pyx is the first disk within a cometary globule to be spatially resolved, and is now the first such disk to be investigated to this extent. The work of this paper could potentially be a first step into the further study of disks in the moderate FUV environment of the Gum Nebula and its globules
Investigating particle acceleration in the Wolf-Rayet bubble NGC 2359
No full textMassive stars have been proposed as potential major factories of Galactic cosmic rays (GCRs). However, this claim lacks sufficient empirical evidence, especially in the case of isolated stars. The powerful stellar winds from massive stars impact the ambient medium and produce strong shocks suitable for accelerating relativistic particles. The detection of nonthermal emission --- particularly synchrotron emission in low-frequency radio bands --- serves as proof of particle acceleration sites.
We assess whether isolated massive stars can be sources of GCRs.
We observed the Wolf-Rayet bubble NGC,2359 using the upgraded Giant Metrewave Radio Telescope in Band 3 (250--500 MHz) and Band 4 (550--950 MHz). Additionally, we utilized complementary archival radio datasets across different frequencies to derive the broad spectral energy distribution (SED) for several regions within the bubble. In addition, to further characterize the interaction between the stellar wind and the ambient medium, we introduced a composite SED model that includes synchrotron and free--free emission, as well as two low-frequency turnover processes, the Razin-Tsytovich (RT) effect and free--free absorption (FFA). We used a Bayesian inference approach to fit the SEDs and constrain the electron number density and magnetic field strength.
The SEDs of several regions across the bubble have spectral indices steeper than -0.5, indicative of synchrotron radiation. Furthermore, the SEDs show a turnover below ∼1 GHz. Our SED modeling suggests that the observed turnover is primarily caused by the RT effect, with a minor contribution from internal FFA.
Our analysis confirms the presence of synchrotron radiation within NGC,2359. This is the second detection of nonthermal emission in a stellar bubble surrounding a Wolf–Rayet star, reinforcing the idea that such environments are sites of relativistic particle acceleration. This finding further supports the hypothesis that isolated massive stars are sources of GCRs of at least GeV energies
Linking Fermi blazars and radio galaxies through accretion and jet radiation mechanisms
No full textBased on the classical unification, blazars, namely BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs), are believed to correspond to radio galaxies, when observed at small jet viewing angles.
In this paper, we aim to compile a sample of blazars Fermi redshift, z∈(0.002-4.313) and radio galaxies z∈(0.001-1.048) to provide new insights into a unified accretion and ejection scenario between aligned and misaligned radio-loud active galactic nuclei, by considering their optical emission-line classifications (low- and high-excitation radio galaxies, LERGs and HERGs, respectively), which are more representative of their accretion states.
We adopted the statistical analyses of accretion properties and high-energy beaming patterns for both blazars and radio galaxies to investigate a unified accretion–ejection scenario. Fermi
In the γ-ray luminosity–photon index plane, HERGs populate the region of higher luminosities and softer photon indices, akin to FSRQs, whereas LERGs fill at lower luminosities with harder photon indices, analogous to BL Lacs. This parallel segregation indicates that LERGs and HERGs represent the misaligned counterparts of BL Lacs and FSRQs, respectively. The unified picture is further supported by the Compton dominance–photon index diagram, whereby FSRQs and HERGs dominated by external Compton (EC) emissions are distinctly separated from BL Lacs and LERGs governed by synchrotron self-Compton (SSC) emissions. Similarly, the diagram of accretion rate versus γ-ray photon index reveals two distinct accretion–ejection states: a low-accretion-rate branch (BL Lacs and LERGs) is associated with the SSC model, and a high-accretion-rate branch (FSRQs and HERGs) is linked to the EC model. These results strongly strengthen the idea of a unified accretion and ejection paradigm between blazars and radio galaxies separating into two distinct states
Analytical modeling of helium absorption signals of isothermal atmospheric escape
No full textAtmospheric escape driven by extreme ultraviolet radiation is a critical process shaping the evolution of close-in exoplanets. Recent observations have detected helium triplet absorption in numerous close-in exoplanets (>20), highlighting the importance of understanding upper atmospheric thermo-chemical structure. While super-solar metallicity has been observed in the atmospheres of some close-in exoplanets, the impact of metal species on both atmospheric escape dynamics and observed absorption features remains poorly understood. In this study, we derived a simplified yet accurate formula for calculating the equivalent width of helium absorption in the limit of an isothermal temperature for the upper atmosphere. Our results demonstrate that planets with lower temperatures (metal-rich atmospheres) exhibit lower mass-loss rates, though the equivalent width of helium triplet absorption remains largely independent of atmospheric temperature (metallicity) because the low temperatures in these atmospheres enhance the fraction of helium in its triplet state. Additionally, we present a hydrodynamic model based on radiation-hydrodynamic simulations that incorporates the effects of metal cooling. Our analytical model can predict the helium triplet equivalent width of the atmosphere in simulations. The analytical model provides a comprehensive framework for understanding how metal cooling in the upper atmosphere influences the thermo-chemical structure and observable helium features of close-in exoplanetary atmospheres, offering valuable insights for interpreting current and future observational data