bluuebunny/crossref_metadata_2025 huggingface dataset:
The restless population of bright X-ray sources of NGC 3621
Authors: Sacchi A. , Imbrogno M. , Motta S. E. , Esposito P. , Israel G. L. , Pinciroli Vago N. O. , De Luca A. , Marelli M. , Pintore F. , Rodríguez Castillo G. A. , Salvaterra R. , Tiengo A.
Published: July 2024

We report on the multi-year evolution of the population of X-ray sources in the nuclear region of NGC 3621 based on Chandra, XMM-Newton, and Swift observations. Among these, two sources, X1 and X5, after their first detection in 2008, seem to have faded below the detectability threshold, a most interesting fact as X1 is associated with the active galactic nucleus (AGN) of the galaxy. Two other sources, X3 and X6, are presented for the first time, the former showing a peculiar short-term variability in the latest available dataset, suggesting an egress from eclipse, and hence belonging to the handful of known eclipsing ultra-luminous X-ray sources. One source, X4, previously known for its heartbeat (i.e. a characteristic modulation in its signal with a period of ≈1 h), shows a steady behaviour in the latest observation. Finally, the brightest X-ray source in NGC 3621, here labelled X2, shows steady levels of flux across all the available datasets, but a change in its spectral shape, reminiscent of the behaviours of Galactic disc-fed X-ray binaries.
The role of outflows in black-hole X-ray binaries
Authors: Kylafis N. D. , Reig P.
Published: July 2024

Context. The hot inner flow in black-hole X-ray binaries is not just a static corona rotating around the black hole: it must be partially outflowing. It is therefore a mildly relativistic “outflowing corona”. We have developed a model in which Comptonization takes place in this outflowing corona. In all of our previous work, we assumed a rather high outflow speed of 0.8c.

Aims. Here, we investigate whether an outflow with a significantly lower speed can also reproduce the observations. Thus, in this work we consider an outflow speed of 0.1c or less.

Methods. As in all of our previous work, we used a Monte Carlo code to compute not only the emergent X-ray spectra, but also the time lags that are introduced to the higher-energy photons with respect to the lower-energy ones via multiple scatterings. We also record the angle (with respect to the symmetry axis of the outflow) and the height at which photons escape.

Results. Our results are very similar to those of our previous work, with some small quantitative differences that can be easily explained. We are again able to quantitatively reproduce five observed correlations: (a) the time lag as a function of Fourier frequency, (b) the time lag as a function of photon energy, (c) the time lag as a function of Γ, (d) the time lag as a function of the cutoff energy in the spectrum, and (e) the long-standing radio–X-ray correlation – and all of them with only two parameters, which vary in the same ranges for all the correlations.

Conclusions. Our model does not require a compact, narrow relativistic jet, although its presence does not affect the results. The essential ingredient of our model is the parabolic shape of the Comptonizing corona. The outflow speed plays a minor role. Furthermore, the bottom of the outflow, in the hard state, looks like a “slab” to the incoming soft photons from the disk, and this can explain the observed X-ray polarization, which is along the outflow. In the hard-intermediate state, we predict that the polarization of GX 339−4 will be perpendicular to the outflow.
Testing cosmic anisotropy with Padé approximations and the latest Pantheon+ sample
Authors: Hu J. P. , Hu J. , Jia X. D. , Gao B. Q. , Wang F. Y.
Published: July 2024

Cosmography can be used to constrain the kinematics of the Universe in a model-independent way. In this work, we attempt to combine the Padé approximations with the latest Pantheon+ sample to test the cosmological principle. Based on the Padé approximations, we first applied cosmographic constraints to different-order polynomials including third-order (Padé(2, 1)), fourth-order (Padé(2, 2)), and fifth-order (Padé(3, 2)) ones. The statistical analyses show that the Padé(2, 1)polynomial has the best performance. Its best fits areH0 = 72.53 ± 0.28 km s−1Mpc−1,q0= −0.35−0.07+0.08, andj0= 0.43−0.56+0.38. By further fixingj0 = 1.00, it can be found that the Padé(2, 1)polynomial can describe the Pantheon+ sample better than the regular Padé(2, 1)polynomial and the usual cosmological models (including the ΛCDM,wCDM, CPL, andRh= ct models). Based on the Padé(2, 1)(j0 = 1) polynomial and the hemisphere comparison method, we tested the cosmological principle and found the preferred directions of cosmic anisotropy, such as (l, b) = (304.6°−37.4+51.4, −18.7°−20.3+14.7) and (311.1°−8.4+17.4, −17.53°−7.7+7.8) forq0andH0, respectively. These two directions are consistent with each other at a 1σconfidence level, but the corresponding results of statistical isotropy analyses including isotropy and isotropy with real positions are quite different. The statistical significance ofH0is stronger than that ofq0; that is, 4.75σand 4.39σfor isotropy and isotropy with real positions, respectively. Reanalysis with fixedq0 = −0.55 (corresponds to Ωm= 0.30) gives similar results. Overall, our model-independent results provide clear indications of a possible cosmic anisotropy, which must be taken seriously. Further testing is needed to better understand this signal.
Luminosity dependence of the multiple cyclotron lines in 4U 0115+63
Authors: Roy Kinjal , Manikantan Hemanth , Paul Biswajit
Published: July 2024

Context. The Be X-ray binary 4U 0115+63 underwent a giant outburst in 2023 with the X-ray luminosity of the source reaching 1038 erg s−1. During the outburst, two target of opportunity observations were made with NuSTAR.

Aims. The main goal of this work is to model the multiple cyclotron scattering features (CRSFs) present in 4U 0115+63 and study their dependence on the luminosity of the source.

Methods. The 3–79 keV broadband X-ray coverage of NuSTAR allowed us to properly model the continuum and investigate the nature of the multiple cyclotron resonance scattering features present in the source spectrum. We used the epoch-folding technique to find the pulsation from the source and also studied the changes in the cyclotron line energy with an order of magnitude variation in the source luminosity.

Results. We detected five cyclotron lines during the 2023 outburst near 12, 16, 24, 34, and 47 keV. The ∼16 keV cyclotron line cannot be harmonically related to the other cyclotron lines at ∼12 keV and ∼24 keV. This indicates the presence of two fundamental lines in the spectrum of 4U 0115+63 at 12 keV and 16 keV.

Conclusions. With the inclusion of the two latest NuSTAR observations, we have expanded the data set of the CRSF line center to encompass a broad range of luminosity. This enables us to comprehensively investigate the relationship between the centroid energy of the cyclotron lines and luminosity. The CRSF line center shows no anticorrelation with luminosity, unlike previously reported. Instead, a weak positive correlation is found in four out of the five detected cyclotron lines of 4U 0115+63. The luminosity variation of the two fundamental CRSFs could be well explained with the prediction from the collisionless shock model. A tentative negative correlation was observed in the fundamental CRSF at 16 keV and its harmonics beyond a “critical luminosity” of 1038 erg/s. This behavior was not present for the 12 keV fundamental CRSF and its harmonic at 24 keV.
Size, albedo, and rotational period of the Hayabusa2# target (98943) 2001 CC21
Authors: Fornasier S. , Dotto E. , Panuzzo P. , Delbo M. , Belskaya I. , Krugly Y. , Inasaridze R. , Barucci M. A. , Perna D. , Brucato J. , Birlan M.
Published: July 2024

Aims. This study aims to determine the size, albedo, and rotational period of (98943) 2001 CC21, a target of the Hayabusa2 extended mission, using thermal data from the Spitzer Space telescope and ground-based observations.

Methods. The Spitzer data were acquired with the Infrared Spectrograph in the 6–38 μm range, reduced using the Spitzer pipeline, and modeled with the near-Earth asteroid thermal model to determine the asteroid size and albedo. The absolute magnitude and rotational period were determined thanks to new observations carried out at the 3.5 m New Technology Telescope, the 1.2 m Observatoire de Haute Provence, and the 0.7 m Abastumani telescope. Three complete light curves were obtained in 2023 and 2024 at the last-mentioned telescope.

Results. We determine an absolute magnitude of H = 18.94 ± 0.05 and a rotational period of 5.02124±0.00001 hours, with a large light curve amplitude of ∼0.8 mag. at a phase angle of 22°, indicating a very elongated shape with an estimated a/b semiaxis ratio ≥1.7, or a close-contact binary body. The emissivity of 2001 CC21 is consistent with that of silicates, and its albedo is 21.6±1.6%. Finally, the spherical-equivalent diameter of 2001 CC21 is 465±15 m.

Conclusions. The albedo value and emissivity determined here, coupled with results from polarimetry and spectroscopy from the literature, confirm that 2001 CC21 is an S-complex asteroid, and not an L-type one as was previously suggested. The size of 2001 CC21 is less than 500 m, which is smaller than its first size estimation (∼700 m). These results are relevant in preparation of the observing strategy for 2001 CC21 of the Hayabusa2 extended mission.
Evolution of Jupiter and Saturn with helium rain
Authors: Howard S. , Müller S. , Helled R.
Published: July 2024

The phase separation between hydrogen and helium at high pressures and temperatures leads to the rainout of helium in the deep interiors of Jupiter and Saturn. This process, also known as “helium rain”, affects their long-term evolution. Modeling the evolution and internal structure of Jupiter and Saturn (and giant exoplanets) relies on the phase diagram of hydrogen and helium. In this work, we simulated the evolution of Jupiter and Saturn with helium rain by applying different phase diagrams of hydrogen and helium and we searched for models that reproduce the measured atmospheric helium abundance in the present day. We find that a consistency between Jupiter’s evolution and the Galileo measurement of its atmospheric helium abundance can only be achieved if a shift in temperature is applied to the existing phase diagrams (−1250 K, +350 K or −3850 K depending on the applied phase diagram). Next, we used the shifted phase diagrams to model Saturn’s evolution and we found consistent solutions for both planets. We confirm that de-mixing in Jupiter is modest, whereas in Saturn, the process of helium rain is significant. We find that Saturn has a large helium gradient and a helium ocean. Saturn’s atmospheric helium mass fraction is estimated to be between 0.13 and 0.16. We also investigated how the applied hydrogen-helium equation of state and the atmospheric model affect the planetary evolution, finding that the predicted cooling times can change by several hundred million years. Constraining the level of super-adiabaticity in the helium gradient formed in Jupiter and Saturn remains challenging and should be investigated in detail in future research. We conclude that further explorations of the immiscibility between hydrogen and helium are valuable as this knowledge directly affects the evolution and current structure of Jupiter and Saturn. Finally, we argue that measuring Saturn’s atmospheric helium content is crucial for constraining Saturn’s evolution as well as the hydrogen-helium phase diagram.
Tetrahedral grids in Monte Carlo radiative transfer
Authors: Lauwers Arno , Baes Maarten , Camps Peter , Vander Meulen Bert
Published: July 2024

Context.To understand the structures of complex astrophysical objects, 3D numerical simulations of radiative transfer processes are invaluable. For Monte Carlo radiative transfer, the most common radiative transfer method in 3D, the design of a spatial grid is important and non-trivial. Common choices include hierarchical octree and unstructured Voronoi grids, each of which has advantages and limitations. Tetrahedral grids, commonly used in ray-tracing computer graphics, can be an interesting alternative option.

Aims.We aim to investigate the possibilities, advantages, and limitations of tetrahedral grids in the context of Monte Carlo radiative transfer. In particular, we want to compare the performance of tetrahedral grids to other commonly used grid structures.

Methods.We implemented a tetrahedral grid structure, based on the open-source library TetGen, in the generic Monte Carlo radiative transfer code SKIRT. Tetrahedral grids can be imported from external applications or they can be constructed and adaptively refined within SKIRT. We implemented an efficient grid traversal method based on Plücker coordinates and Plücker products.

Results.The correct implementation of the tetrahedral grid construction and the grid traversal algorithm in SKIRT were validated using 2D radiative transfer benchmark problems. Using a simple 3D model, we compared the performance of tetrahedral, octree, and Voronoi grids. With a constant cell count, the octree grid outperforms the tetrahedral and Voronoi grids in terms of traversal speed, whereas the tetrahedral grid is poorer than the other grids in terms of grid quality. All told, we find that the performance of tetrahedral grids is relatively poor compared to octree and Voronoi grids.

Conclusions.Although the adaptively constructed tetrahedral grids might not be favourable in most media representative of astrophysical simulation models, they still form an interesting unstructured alternative to Voronoi grids for specific applications. In particular, they might prove useful for radiative transfer post-processing of hydrodynamical simulations run on tetrahedral or unstructured grids.
MUSE Analysis of Gas around Galaxies (MAGG)
Authors: Galbiati Marta , Dutta Rajeshwari , Fumagalli Michele , Fossati Matteo , Cantalupo Sebastiano
Published: July 2024

We present a novel dataset that extends our view of the cosmic gas around z ≈ 3 − 4 Lyα emitters (LAEs) in the Muse Analysis of Gas around Galaxies (MAGG) survey by tracing a cool and enriched gas phase through 47 Mg II absorbers identified in newly obtained VLT/X-shooter near-infrared quasar spectra. Jointly with the more ionized gas traced by C IV systems and the neutral H I from previous work, we find that LAEs are distributed inside cosmic structures that contain multiphase gas in composition and temperature. All gas phases are a strong function of the large-scale galaxy environment: the Mg II and the C IV strength and kinematics positively correlate with the number of associated galaxies, and it is ≈3 − 4 times more likely to detect metal absorbers around groups of LAEs than isolated ones. Exploring the redshift evolution, the covering factor of Mg II around groups of LAEs and isolated ones remains approximately constant from z ≈ 3 − 4 to z ≲ 2, but the one of C IV around group galaxies drops by z ≲ 2. Adding the cool enriched gas traced by the Mg II absorbers to the results that we obtained for the H I and C IV gas, we put forward a picture in which LAEs lie along gas filaments that contain high column-density H I systems and are enriched by strong C IV and Mg II absorbers. While the Mg II gas appears to be more centrally concentrated near LAEs, weaker C IV systems instead trace a more diffuse gas phase extended up to larger distances around the galaxies.
FAUST
Authors: Podio L. , Ceccarelli C. , Codella C. , Sabatini G. , Segura-Cox D. , Balucani N. , Rimola A. , Ugliengo P. , Chandler C. J. , Sakai N. , Svoboda B. , Pineda J. , De Simone M. , Bianchi E. , Caselli P. , Isella A. , Aikawa Y. , Bouvier M. , Caux E. , Chahine L. , Charnley S. B. , Cuello N. , Dulieu F. , Evans L. , Fedele D. , Feng S. , Fontani F. , Hama T. , Hanawa T. , Herbst E. , Hirota T. , Jiménez-Serra I. , Johnstone D. , Lefloch B. , Le Gal R. , Loinard L. , Baobab Liu H. , López-Sepulcre A. , Maud L. T. , Maureira M. J. , Menard F. , Miotello A. , Moellenbrock G. , Nomura H. , Oba Y. , Ohashi S. , Okoda Y. , Oya Y. , Sakai T. , Shirley Y. , Testi L. , Vastel C. , Viti S. , Watanabe N. , Watanabe Y. , Zhang Y. , Zhang Z. E. , Yamamoto S.
Published: July 2024

Context. Recent observations suggest that planet formation starts early, in protostellar disks of ≤105 yr, which are characterized by strong interactions with the environment, such as through accretion streamers and molecular outflows.

Aims. To investigate the impact of such phenomena on the physical and chemical properties of a disk, it is key to understand what chemistry planets inherit from their natal environment.

Methods. In the context of the ALMA large program Fifty AU Study of the chemistry in the disk/envelope system of solar-like protostars (FAUST), we present observations on scales from ∼1500 au to ∼60 au of H2CO, HDCO, and D2CO toward the young planet-forming disk IRS 63.

Results. The H2CO probes the gas in the disk as well as in a large scale streamer (∼1500 au) impacting onto the southeast disk side. We detected for the first time deuterated formaldehyde, HDCO and D2CO, in a planet-forming disk and HDCO in the streamer that is feeding it. These detections allowed us to estimate the deuterium fractionation of H2CO in the disk: [HDCO]/[H2CO] ∼ 0.1 − 0.3 and [D2CO]/[H2CO] ∼ 0.1. Interestingly, while HDCO follows the H2CO distribution in the disk and in the streamer, the distribution of D2CO is highly asymmetric, with a peak of the emission (and [D]/[H] ratio) in the southeast disk side, where the streamer crashes onto the disk. In addition, D2CO was detected in two spots along the blue- and redshifted outflow. This suggests that (i) in the disk, HDCO formation is dominated by gas-phase reactions in a manner similar to H2CO, while (ii) D2CO is mainly formed on the grain mantles during the prestellar phase and/or in the disk itself and is at present released in the gas phase in the shocks driven by the streamer and the outflow.

Conclusions. These findings testify to the key role of streamers in the buildup of the disk concerning both the final mass available for planet formation and its chemical composition.
Filling in the blanks
Authors: Callingham Thomas M. , Helmi Amina
Published: July 2024

Context. In the solar neighbourhood, only ∼2% of stars in the Gaia survey have a line-of-sight velocity (vlos) contained within the RVS catalogue. These limitations restrict conventional dynamical analysis, such as finding and studying substructures in the stellar halo.

Aims. We aim to present and test a method to infer a probability density function (PDF) for the missing vlos of a star with 5D information within 2.5 kpc. This technique also allows us to infer the probability that a 5D star is associated with the Milky Way’s stellar Disc or the stellar Halo, which can be further decomposed into known stellar substructures.

Methods. We use stars from the Gaia DR3 RVS catalogue to describe the local orbital structure in action space. The method is tested on a 6D Gaia DR3 RVS sample and a 6D Gaia sample crossmatched to ground-based spectroscopic surveys, stripped of their true vlos. The stars predicted vlos, membership probabilities, and inferred structure properties are then compared to the true 6D equivalents, allowing the method’s accuracy and limitations to be studied in detail.

Results. Our predicted vlos PDFs are statistically consistent with the true vlos, with accurate uncertainties. We find that the vlos of Disc stars can be well-constrained, with a median uncertainty of 26 km s−1. Halo stars are typically less well-constrained with a median uncertainty of 72 km s−1, but those found likely to belong to Halo substructures can be better constrained. The dynamical properties of the total sample and subgroups, such as distributions of integrals of motion and velocities, are also accurately recovered. The group membership probabilities are statistically consistent with our initial labelling, allowing high-quality sets to be selected from 5D samples by choosing a trade-off between higher expected purity and decreasing expected completeness.

Conclusions. We have developed a method to estimate 5D stars’ vlos and substructure membership. We have demonstrated that it is possible to find likely substructure members and statistically infer the group’s dynamical properties.
Re-evaluating the cosmological redshift: Insights into inhomogeneities and irreversible processes
Authors: Tremblin P. , Chabrier G.
Published: July 2024

Aims. Understanding the expansion of the Universe remains a profound challenge in fundamental physics. The complexity of solving general relativity equations in the presence of intricate, inhomogeneous flows has compelled cosmological models to rely on perturbation theory in a homogeneous Friedmann–Lemaître–Robertson-Walker background. This approach accounts for a redshift of light encompassing contributions from both the cosmological background expansion along the photon’s trajectory and Doppler effects at emission due to peculiar motions. However, this computation of the redshift is not covariant, as it hinges on specific coordinate choices that may distort physical interpretations of the relativity of motion.

Methods. In this study we show that peculiar motions, when tracing the dynamics along time-like geodesics, must contribute to the redshift of light through a local volume expansion factor, in addition to the background expansion. By employing a covariant approach to redshift calculation, we address the central question of whether the cosmological principle alone guarantees that the averaged local volume expansion factor matches the background expansion.

Results. We establish that this holds true only in scenarios characterised by a reversible evolution of the Universe, where inhomogeneous expansion and compression modes compensate for one another. In the presence of irreversible processes, such as the dissipation of large-scale compression modes through matter virialisation and associated entropy production, the averaged expansion factor becomes dominated by expansion in voids that can no longer be compensated for by compression in virialised structures. Furthermore, for a universe in which a substantial portion of its mass has undergone virialisation, adhering to the background evolution on average leads to significant violations of the second law of thermodynamics. Our approach shows that entropy production due to irreversible processes during the formation of structures plays the same role as an effective, time-dependent cosmological constant (i.e. dynamical dark energy) without the need to invoke new unknown physics. Our findings underscore the imperative need to re-evaluate the influence of inhomogeneities and irreversible processes on cosmological models, shedding new light on the intricate dynamics of our Universe.
INTEGRAL/IBIS polarization detection in the hard and soft intermediate states of Swift J1727.8−1613
Authors: Bouchet T. , Rodriguez J. , Cangemi F. , Thalhammer P. , Laurent P. , Grinberg V. , Wilms J. , Pottschmidt K.
Published: July 2024

Aims. Soft γ-ray emission (100 keV–10 MeV) has previously been detected in the hard state of several microquasars. In some sources, this emission was found to be highly polarized and was suggested to be emitted at the base of the jet. Until now, no γ-ray polarization had been found in any other state.

Methods. Using INTEGRAL/IBIS, we studied the soft γ-ray spectral and polarization properties of Swift J1727.8−1613 throughout its outburst.

Results. We detect a highly polarized spectral component in both the hard intermediate state and the early stages of the soft intermediate state above 210 keV. In the hard intermediate state, the polarization angle significantly deviates from the compact jet angle projected onto the sky, whereas in the soft intermediate they are closely aligned. This constitutes the first detection of jet-aligned polarization in the soft γ-ray for a microquasar. We attribute this polarized spectral component to synchrotron emission from the jet, which indicates that some of the jet might persist into the softer states.
A study of centaur (54598) Bienor from multiple stellar occultations and rotational light curves
Authors: Rizos J. L. , Fernández-Valenzuela E. , Ortiz J. L. , Rommel F. L. , Sicardy B. , Morales N. , Santos-Sanz P. , Leiva R. , Vara-Lubiano M. , Morales R. , Kretlow M. , Alvarez-Candal A. , Holler B. J. , Duffard R. , Gómez-Limón J. M. , Desmars J. , Souami D. , Assafin M. , Benedetti-Rossi G. , Braga-Ribas F. , Camargo J. I. B. , Colas F. , Lecacheux J. , Gomes-Júnior A. R. , Vieira-Martins R. , Pereira C. L. , Morgado B. , Kilic Y. , Redfield S. , Soloff C. , McGregor K. , Green K. , Midavaine T. , Schreurs O. , Lecossois M. , Boninsegna R. , Ida M. , Le Cam P. , Isobe K. , Watanabe Hayato , Yuasa S. , Watanabe H. , Kidd S.
Published: July 2024

Context. Centaurs, distinguished by their volatile-rich compositions, play a pivotal role in understanding the formation and evolution of the early Solar System, as they represent remnants of the primordial material that populated the outer regions. Stellar occultations offer a means to investigate their physical properties, including shape and rotational state, and the potential presence of satellites and rings.

Aims. This work aims to conduct a detailed study of the centaur (54598) Bienor through stellar occultations and rotational light curves from photometric data collected during recent years.

Methods. We successfully predicted three stellar occultations by Bienor that were observed from Japan, Western Europe, and the USA. In addition, we organized observational campaigns from Spain to obtain rotational light curves. At the same time, we developed software to generate synthetic light curves from three-dimensional shape models, enabling us to validate the outcomes through computer simulations.

Results. We resolved Bienor’s projected ellipse for December 26, 2022; determined a prograde sense of rotation; and confirmed an asymmetric rotational light curve. We also retrieved the axes of its triaxial ellipsoid shape as a = (127 ± 5) km, b = (55 ± 4) km, and c = (45 ± 4) km. Moreover, we refined the rotation period to 9.1736 ± 0.0002 h and determined a geometric albedo of (6.5 ± 0.5)%, which is higher than previously determined by other methods. Finally, by comparing our findings with previous results and simulated rotational light curves, we analyzed whether an irregular or contact-binary shape, an additional element such as a satellite, or significant albedo variations on Bienor’s surface may be present.
Unveiling complex magnetic field configurations in red giant stars
Authors: Das S. B. , Einramhof L. , Bugnet L.
Published: July 2024

The recent measurement of magnetic field strength inside the radiative interior of red giant stars has opened the way toward full 3D characterization of the geometry of stable large-scale magnetic fields. However, current measurements, which are limited to dipolar (ℓ = 1) mixed modes, do not properly constrain the topology of magnetic fields due to degeneracies on the observed magnetic field signature on such ℓ = 1 mode frequencies. Efforts focused toward unambiguous detections of magnetic field configurations are now key to better understand angular momentum transport in stars. We investigated the detectability of complex magnetic field topologies (such as the ones observed at the surface of stars with a radiative envelope with spectropolarimetry) inside the radiative interior of red giants. We focused on a field composed of a combination of a dipole and a quadrupole (quadrudipole) and on an offset field. We explored the potential of probing such magnetic field topologies from a combined measurement of magnetic signatures on ℓ = 1 and quadrupolar (ℓ = 2) mixed mode oscillation frequencies. We first derived the asymptotic theoretical formalism for computing the asymmetric signature in the frequency pattern for ℓ = 2 modes due to a quadrudipole magnetic field. To access asymmetry parameters for more complex magnetic field topologies, we numerically performed a grid search over the parameter space to map the degeneracy of the signatures of given topologies. We demonstrate the crucial role played by ℓ = 2 mixed modes in accessing internal magnetic fields with a quadrupolar component. The degeneracy of the quadrudipole compared to pure dipolar fields is lifted when considering magnetic asymmetries in both ℓ = 1 and ℓ = 2 mode frequencies. In addition to the analytical derivation for the quadrudipole, we present the prospect for complex magnetic field inversions using magnetic sensitivity kernels from standard perturbation analysis for forward modeling. Using this method, we explored the detectability of offset magnetic fields from ℓ = 1 and ℓ = 2 frequencies and demonstrate that offset fields may be mistaken for weak and centered magnetic fields, resulting in underestimating the magnetic field strength in stellar cores. We emphasize the need to characterize ℓ = 2 mixed-mode frequencies, (along with the currently characterized ℓ = 1 mixed modes), to unveil the higher-order components of the geometry of buried magnetic fields and to better constrain angular momentum transport inside stars.
Exploring fluorine chemical evolution in the Galactic disk: The open cluster perspective
Authors: Bijavara Seshashayana S. , Jönsson H. , D’Orazi V. , Sanna N. , Andreuzzi G. , Nandakumar G. , Bragaglia A. , Romano D. , Spitoni E.
Published: July 2024

Context. Open clusters are ideal tools for tracing the abundances of different elements because their stars are expected to have the same age, distance, and metallicity. Therefore, they serve as powerful tracers for investigating the cosmic origins of elements. This paper expands on a recent study by us, in which the element fluorine was studied in seven open clusters; here we add six open clusters and eight field stars.

Aims. The primary objective is to determine the abundance of fluorine (F) to gain insight into its production and evolution. The magnesium (Mg) abundances were derived to categorize the field stars into high and low alpha disk populations. Additionally, cerium (Ce) abundances were determined to better understand the interplay between F and s-process elements. Our goal is to analyze the trend of F abundances across the Galactic disk based on metallicity and age. By comparing observational data with Galactic chemical evolution models, the origin of F can be better understood.

Methods. The spectra were obtained from the high-resolution near-infrared GIANO-B instrument at the Telescopio Nazionale Galileo (TNG). For the derivation of the stellar parameters and abundances, the Python version of Spectroscopy Made Easy (PySME) was used. OH, CN, and CO molecular lines and band heads along with Fe I lines were used to determine the stellar parameters in the H-band region. Two HF lines in the K band (λλ 2.28, and 2.33 μm), three K-band Mg I lines (λλ 2.10, 2.11, and 2.15 μm), and two Ce II lines in the H band (λλ 1.66, and 1.71 μm) were used to derive the abundances of F, Mg, and Ce, respectively.

Results. F, Mg, and Ce abundances were derived for 14 stars from 6 OCs, as well as for 8 field stars. The F and Ce abundances were investigated as a function of metallicity, age, and galactocentric distance. We also compared our findings with different Galactic chemical evolution models.

Conclusions. Our results indicate that asymptotic giant branch stars and massive stars, including a subset of fast rotators (whose rotation speed likely increases as metallicity decreases), are necessary to explain the cosmic origin of F. This finding is consistent with and, with the large sample size, reinforces the conclusion of our previous study.
Diversité des exploitations agricoles d’oasis de montagne : une analyse par le travail, les revenus et le couplage entre cultures et élevage
Authors: Sraïri Mohamed Taher , Amartini Hakim
Published: July 2024

Les oasis de montagne d’Afrique du Nord subissent de plein fouet les effets du changement climatique, qui amplifient l’ensemble des contraintes agronomiques : foncier exigu, aridité structurelle, etc. Dans cette étude, l’objectif est d’analyser les différentes dimensions du couplage entre cultures et élevage et leurs effets sur le fonctionnement des systèmes de production. Trente exploitations des communes de M’semrir et Tilmi (1900 m d’altitude, Haut Atlas central, Maroc) ont été retenues. Les durées de travail agricole et les revenus annuels générés par les différentes spéculations ont été déterminés. Une typologie d’exploitations agricoles a été établie sur la base des données de fonctionnement collectées. Elle a révélé les cinq types suivants, illustrant les différences de localisation géographique : i) élevage transhumant et cultures diversifiées ; ii) élevages sédentaires avec un important volume de travail familial ; iii) couplage cultures de rente et élevage sédentaire ; iv) élevage sédentaire basé sur les cultures fourragères ; et v) exploitations de vergers et d’élevage avec un épandage massif de fumier. Les résultats ont montré que le travail alloué à l’élevage représente plus de la moitié (57 %) du temps de travail total, illustrant son importance, puisqu’il est aussi associé à près de la moitié (49 %) des revenus agricoles. Ce travail dédié à l’élevage est assumé presque exclusivement (93 %) par de la main-d’œuvre familiale. Cette dernière participe aussi aux travaux liés aux cultures (66 %). Le pommier en occupe l’essentiel (57 %), suivi des céréales (29 %) et du maraîchage (14 %). Un jour de travail est rémunéré en moyenne à 7,5 € pour l’élevage ; 23,6 € pour le pommier ; 6,1 € pour les céréales et 3,7 € pour le maraîchage.
A study on the importance of mutual funds as an investment tool
Authors: Indira D. , Sah Vanisree , Tanvi P. , Sai Deepika P. , Anvith Reddy P.
Published: July 2024

Mutual Funds play an important role in helping small, medium and large savers across the globe by reducing risk and increasing return. Mutual Funds have contributed in a big way in the transformation of Indian economy by setting a platform through the financial markets. The objectives of the present study is to analyse the growth of Mutual Fund Industry in India. The data used for the study is secondary and descriptive method is used in analysis. It is found that MF’s have grown significantly. The reasons behind their growth have been the tax benefits, the growth strategies and SEBI as a regulator has played a pivotal role in ensuring transparency in the mechanism.
Investigation of tempered AISI 420 SS under dry slided conditions for sustainable applications
Authors: Kumar S.N.S. Santhosh , Vinoth R. , Kumar Rajesh , Kumar M. Jeevan , Prasad D.V.S.S.S.V. , Prabhu S. , Ram S.
Published: July 2024

Martensitic stainless steel exhibits a lower corrosion resistance, higher hardness, wear resistance, and strength, but no ductility. As a result, tempering techniques have been used to stabilise the ductility. AISI 420 stainless were chosen and prepared in cylindrical shape for a dimension of 35 mm length, 10 mm diameter. The specimens were tempered to 245°C, 345°C, 445°C temperatures respectively and termed as T1, T2 and T3. The material which is not treated is kept on the other side for results comparison. Testing of hardness was taken up by Rockwell method. Wear tests were carried out for all the specimens using pin-on disc wear analyser. The changes in microstructure were distinguished with all the samples and were captured by electron microscopic techniques. The goal of the test is to determine, the best treated specimen suited for a particular application. It was noted that, phase change from martensite stage to residual austenite is determined.
Assessment of wear behavior analysis on normalized martensitic stainless steel for sustainable applications
Authors: Sathish S. , Beena T. , Rahul V. , Kumar M. Saravana , Das A. Daniel , Seema Banu , Ram Ramaswamy
Published: July 2024

An alloy of iron and chromium is called stainless steel. The compositionratio of stainless steel will vary depending on the grade required and the intended use of the steel, although it must contain at least 0.5% chromium. Numerous applications exist for stainless steel in the industrial and consumer markets because of its superior corrosion resistance, high strength and good appearance aesthetic wise. Because of the chemical composition, martensitic steel is a kind of stainless steel that can be strengthened, hardened with heat and ageing processes. Because of these techniques, Martensitic steel is stronger than other kinds, which makes it a good option for manufacturing mechanical valves, turbine parts, medical equipment applications. AISI 410 martensitic stainless are strong and wear resistant one. The usage of this material is limited because of its hardness. For enhancing the ductility, these steels were subjected to normalizing process at 740°C, 840°C, 940°C and designated as N1, N2, N3 respectively. The samples were made cylindrical in shape with 11 mm diameter, length of 40 mm. The outcomes of the results like measurement of hardness, loss of wear were noted down and comparisons of microstructures with all the samples were carried out.
Synthesis and effect of epoxy in lamination for Kevlar / E-glass hybrid composites
Authors: Kumar P. Ravi , Reddy G. Shashank , Rohith P. , Karthik S. Sai
Published: July 2024

A combination of their unique stiffness and strength, hybrid composites has great potential in a variety of industries, including medium-duty automotive, aircraft, and submarines. In order to evaluate the performance of kevlar/E-glass epoxy composites in this article concentrated on their fabrication and testing. It is well known that the composition has a major impact on the mechanical properties and functional traits of the composite. In order to ascertain the ideal epoxy mix, we thus used a manual layup technique to produce three unique composite sheets designated as P (2:3), Q (2:4), and R (3:2). Research follow ASTM guidelines while analyzing the mechanical parameters, concentrating on tensile strength and binding strength to assess overall structural integrity. As a way to find the interlayer laminar strength between Kevlar fibre and epoxy provide information on interfacial properties, delamination experiments were also carried out. Comparing composite sample P (2:3) to other compositions, our results showed that it had the lowest swelling ratio and the best mechanical qualities. Composite sample Q (2:4), on the other hand, showed the best interlaminar characteristics and adhesion capabilities. The significance of composition mix in attaining targeted performance attributes in hybrid composites is highlighted by these findings.
Optimizing Mix Proportion of Geopolymer Concrete with Steel Sludge - A Sustainable Approach
Authors: Selvakumar M. , Geetha S. , C Janahar , Krishnan S Lakshmi , Kumar R Rohith
Published: July 2024

As the construction industry is moving towards sustainable infrastructure, the need for green construction materials has gained importance in current scenario. Geopolymer concrete is considered to be an alternate to conventional concrete with cement as cement production is considered to emit more greenhouse gases into the atmosphere. This work has still raised the sustainable part of the geopolymer concrete by using steel sludge generated from automobile industry as partial replacement for fine aggregate. The experimental results were designed using fractional factorial design. The results were analysed for statistical integrity with ANOVA. It has been observed that the maximum compressive strength achieved with steel sludge up to 30% replacement is 48 Mpa with flexural strength of 5.16 Mpa and split tensile strength of 4.6 Mpa. Optimisation was done to find the proportion that gives maximum strength and it was ascertained with experimental validation. XRD and SEM analysis were carried out for studying the microstructure and reaction products formed in the process.
Non-contact structure solar desalination system for higher depths
Authors: Uday Kiran Matta , Kumar Kaviti Ajay
Published: July 2024

To address the worldwide issue of water scarcity, prompt action is required. Solar desalination is one potential sustainable solution that could be considered for this problem. A nano-structure solar still that does not require touch is the subject of this investigation. As a result of the non-contact structure, the solar still structure does not meet water, which not only extends its lifespan but also prevents salt from accumulating when it is doing continuous operation. One side of the non-contact structure is made to be a high absorber of sun’s light, while the other side is made to be a high emitter of the infrared wavelength. A total of three and four centimeters of saline water were used in the experiments that were conducted. The information was gathered over the course of three months to evaluate the performance of the construction in a variety of specific environmental conditions. Several characteristics, such as glass, basin, vapor, water, absorber, ambient temperature, time, and solar intensity, were measured over the course of the experiment. In proportion to the increasing water depth, the NCNS system generates a greater quantity of distillate than the CSS system. When compared to the CSS approach, it generates 15% and 8% more distillate for depths of 3 cm and 4 cm, respectively. Hence, non-contact structure is sustainable solution for solar desalination.
Mechanical and wear behavior of al-steel solid state cladding produced by friction stir surfacing
Authors: Badheka Kedar , Kumar Sharma Daulat , Badheka Vishvesh
Published: July 2024

Friction surfacing (FS) is a solid-state cladding method that produces a coating with minimum dilution and good metallurgical bonding. Deposition of aluminium over mild steel with using fusion based joining process is not feasible sue to the formation of iron aluminide and Fe and Al are metallurgically immiscible to each other. Hence, deposition of aluminium on steel with solid-state condition is feasible and most viable option. During the process, a rotating consumable rod is rubbed against the substrate plate under an applied axial load. The friction between rod and substrate generates a visco-plastic layer at the end of rod tip. The high temperature and pressure at interfaces aids in the cladding of the rod material on the substrate. Aluminium alloy 6351 T6 rod of 22 mm diameter was used as consumable material for surfacing on a 6mm thick SA516 Gr70 steel substrate plate. Optimized process parameters were used for the final experimental trials. Multilayer samples generated at constant Friction Surfacing variables were subjected to Pin-on-disc wear test at 40N load. Mechanical interlocking was also observed at the interface of the layers. The process was also observed to produce extremely fine grain microstructures of the deposited material due to the hot forging action involved resulting in superior wear properties.
Sustainable Improvements in Mechanical and Tribological Properties of AA2017-Aluminum Nitride Composites: A Comprehensive Investigation and Numerical Analysis
Authors: R Senthil , Vinayagam M.
Published: July 2024

An AA2017-aluminum nitride composite was created through stir casting, and its tribological properties, like hardness and wear rate were examined by varying the aluminum nitride content from 5% to 15%. A numerical model was established to predict the wear rates of aluminum metal matrix composites (MMCs), and the accuracy of the model was confirmed through an analysis of variance (ANOVA). The findings demonstrated that the addition of aluminum nitride to AA2017 resulted in improved mechanical and wear characteristics for the composites. Furthermore, the utilization of sustainable materials and manufacturing techniques underscores the potential for environmentally responsible engineering solutions in material science and manufacturing processes. Aluminum nitride emerged as a critical component in enhancing the wear resistance of the metal matrix composites, contributing to their overall durability and sustainability.
Recent Reviews on Hybrid Nano Reinforcements for Improving Mechanical Properties of Polymers for sustainable applications
Authors: B Seema , Girisha L. , Subbiah Ramaswamy , T P Jeevan
Published: July 2024

The paper reviews the impact of hybrid nano particles in polymers that would enhance the mechanical properties. Various nano fillers have been used as reinforcements that would improve the mechanical properties of the composite materials. Poly methly methacrylate (PMMA) is preferred as the matrix material especially in denture bases as it overcomes the deficiencies that the other materials show. (PMMA) is an acrylic resin commonly used with a long heritage for prosthetic reasons. It can be classed as chemically or thermally polymerized material based on the causes that trigger the reaction. The nano fillers when used as reinforcements in PMMA have shown very good results. The microstructure behavior of the distribution of the nanofillers were studied through XRD, SEM, AFM and other techniques. Some studies have used optimization techniques to compare the results.
A Detailed Review on Sustainable Engineering Methods Integrated with Waste Management Practices
Authors: Bandhu Din , Umashankari E. , V Revathi , Dutt Amit , Kumar Pramod , Ali Abd Ulabbas Abedi Tamam
Published: July 2024

Environmental engineering is a broad field that considers the complex interactions between natural issues and human action to make long-term arrangements and provide solutions. Natural designing uses many principles from the field of chemistry science, material technology, and other research to analyse and carry out strategies for resource conservation, protecting the environment, and the minimization of contaminated particles and polluting substances. The focus of the paper is on the sustainable and waste management practices that can reduce the undesirable effects such as carbon prints on the environment. the framework has been designed to attract more and more industries and management to achieve the sustainable growth of the sector. The key objectives of remediation activities are to safeguard public health, repair harmed ecosystems, and encourage the long-term, sustainable use of contaminated land or that area. Environmental engineering will continue to be essential in helping to shape a more sustainable relationship between humans and the natural world as society faces constantly shifting ecological issues and all the challenges related to the environment.
Development of a Sustainable Nano-refrigerant using agro-waste (rice husk ash) as a base material for a domestic refrigeration system
Authors: Ikumapayi Omolayo M. , Afolalu Sunday A. , Laseinde Opeyeolu T. , Ogedengbe Temitayo S. , Akinlabi Stephen A. , Akinlabi Esther T.
Published: July 2024

Silica nanoparticles were synthesized from Rice husk ash (RHA) through the top-down approach production greyish coloured particles. The spectroscopical investigation showed a compositional analysis of 74.6% silicon, 20% oxygen and 5.4% carbon. Microstructural studies indicated an average particle area of 7.8nm2 and average particle size of 4nm. The nanoparticles were dispersed into the lubricant oil of the compressor such that when the refrigerant is dispersed over the compressor, the particles mix with the refrigerant giving the nano-refrigerant mixture. The nanoparticles were dispersed into the mineral oil at concentrations of 0.2wt%, 0.3 wt%, 0.5 wt% and 0.6 wt% and fed into the compressor to combine with the refrigerant in the vapour compression system. The refrigerator was run for 240 minutes for each sample as well as the control sample which was the refrigerant R600a. Performance evaluation was carried out to assess the viability of the developed nano-refrigerant. Generally, an increase in the refrigerating effect compared to the control sample by all concentrations apart from the 0.6wt% by 13, 7.5, and 12.5% and a corresponding increase in the COP by 31, 23 and 35% compared to the control sample for the 0.2 wt%, 0.3 wt% and 0.5 wt% concentrations respectively was recorded.