Binary Systems Research Articles

Self-interacting axion clouds around rotating black holes in binary systems

Self-interacting axion clouds around rotating black holes in binary systems

Studying Intermolecular Interactions in Binary Systems of Butyl Acetate-Dibutyl Phthalate and Butyl Acetate-Dioctyl Phthalate

Studying Intermolecular Interactions in Binary Systems of Butyl Acetate-Dibutyl Phthalate and Butyl Acetate-Dioctyl Phthalate

Key phase diagram experiments and thermodynamic modeling of the ZnO‒B2O3, ZnO‒SiO2, and ZnO‒B2O3‒SiO2 systems

AbstractThermodynamic modeling of binary ZnO‒B2O3 and ZnO‒SiO2 systems and ternary ZnO‒B2O3‒SiO2 system were carried out based on the critical evaluation and optimization of all available phase diagram and thermodynamic property data using the CALculation of PHAse Diagram (CALPHAD) method. To resolve the inconsistency among the available phase diagram data in ternary ZnO‒B2O3‒SiO2 system, key phase diagram experiment was carried out using classical quenching method followed by electron probe micro‐analysis and X‐ray diffraction phase determination. The liquid oxide solution was described using the modified quasichemical model accounting for a short‐range ordering behavior in molten oxide solution. Thermodynamic models with optimized model parameters were used to predict the phase diagram and thermodynamic properties of the ternary systems.

On the non-dissipative orbital evolution of a binary system comprising non-compact components with misaligned spin and orbital angular momenta

Abstract In this Paper we determine the non-dissipative tidal evolution of a close binary system with an arbitrary eccentricity in which the spin angular momenta of both components is misaligned with the orbital angular momentum. We focus on the situation where the orbital angular momentum dominates the spin angular momenta and so remains at small inclination to the conserved total angular momentum. Torques arising from rotational distortion and tidal distortion taking account of Coriolis forces are included. This extends the previous work of Ivanov & Papaloizou relaxing the limitation resulting from the assumption that one of the components is compact and has zero spin angular momentum. Unlike the above study, the evolution of spin-orbit inclination angles is driven by both types of torque. We develop a simple analytic theory describing the evolution of orbital angles and compare it with direct numerical simulations. We find that the tidal torque prevails near ’critical curves’ in parameter space where the time-averaged apsidal precession rate is close to zero. In the limit of small spin, these curves exist only for systems that have at least one component with retrograde rotation. As in our previous work, we find solutions close to these curves for which the apsidal angle librates. As noted there, this could result in oscillation between prograde and retrograde states. We consider the application of our approach to systems with parameters similar to those of the misaligned binary DI Herc.

Variable structures in the stellar wind of the HMXB Vela X-1

Strong stellar winds are an important feature in wind-accreting high-mass X-ray binary (HMXB) systems. Exploring their structure provides valuable insights into stellar evolution and their influence on surrounding environments. However, the long-term evolution and temporal variability of these wind structures are not fully understood. This work probes the archetypal wind-accreting HMXB Vela X-1 using the Monitor of All-sky X-ray Image (MAXI) instrument to study the orbit-to-orbit absorption variability in the $2–10$ keV energy band across more than 14 years of observations. Additionally, the relationship between hardness ratio trends in different binary orbits and the spin state of the neutron star is investigated. We calculated X-ray hardness ratios to track absorption variability, comparing flux changes across various energy bands, as the effect of absorption on the flux is energy-dependent. We assessed variability by comparing the hardness ratio trends in our sample of binary orbits to the long-term averaged hardness ratio evolution derived from all available MAXI data. Consistent with prior research, the long-term averaged hardness ratio evolution shows a stable pattern. However, the examination of individual binary orbits reveals a different hardness ratio evolution between consecutive orbits with no evident periodicity within the observed time span. We find that fewer than half of the inspected binary orbits align with the long-term averaged hardness evolution. Moreover, neutron star spin-up episodes exhibit more harder-than-average hardness trends compared to spin-down episodes, although their distributions overlap considerably. The long-term averaged hardness ratio dispersion and evolution are consistent with absorption column densities reported in literature from short observations, indicating that a heterogeneous wind structure -- from accretion wakes to individual wind clumps -- likely drives these variations. The variability observed from orbit to orbit suggests that pointed X-ray observations provide limited insights into the overall behaviour of the wind structure. Furthermore, the link between the spin state of the neutron star and the variability in orbit-to-orbit hardness trends highlights the impact of accretion processes on absorption. This connection suggests varying accretion states influenced by fluctuations in stellar wind density.

Tracking the influence of a very close secondary star on planetary growth and evolution

Abstract This work investigated the dynamics of planets in binary systems and provided insights into the stability and evolution of these systems. We explored the influence of a nearby secondary star on planetary growth and evolution, focusing on S-type configurations. We tracked the orbits of the planets and analyzed their stability over long timescales, considering various parameters such as mass, eccentricity, and inclination. Our results show that the presence of a secondary star can significantly impact the growth and evolution of planets, leading to changes in their orbits and potential ejection from the system, however, it was possible to identify stable planets even in systems experiencing multiple disturbances. One of the most significant results of the work was the analysis of the increased material in the disc near the primary star, which contributes to planet growth, driven by the density spirals influenced by the binary star.These findings have important implications for the search for habitable exoplanets and emphasize the need for further studies of planetary systems in binary star environments.

Spatially Coded Transformations in Gradient‐Dependent Protocell Morphogenesis

AbstractChemical gradients provide spatiotemporal signaling fields in various cellular processes, driving complex dynamic behaviours such as differentiation and spatial organization. Here we employ opposing gradients of two artificial morphogens (sodium dodecyl sulfate (SDS) and sodium phosphotungstate (polyoxometalate; POM)) to systematically investigate morphological differentiation in organized populations of coacervate microdroplet‐based protocells. Using a matrix of 16 sets of counter‐diffusive gradients, we classify the differentiated protocells into five phenotypes and encode their spontaneous organization into different spatially patterned protocell consortia using a 3‐bit binary information system. We show that a predominant SDS gradient produces a diversity of differentiated phenotypes to generate complex spatially coded 2D protocell organizations. In contrast, a prevailing POM gradient decreases morphological differentiation, resulting in population homogenization. Our results improve our understanding of gradient concentration‐dependent collective responses in synthetic microscale agents and provide a step to a new spatially resolved information encoding method with 3‐bit binary outputs.

Spatiotemporal Analysis of the Coupling Relationship Between Urban Infrastructure and Land Utilization in a Shrinking City: A Case Study of Hegang, Northeast China

Globally, urbanization is accelerating, with China witnessing a significant 40% rise in urbanization rate over the past 4 decades. However, the dynamic changes in the spatial coupling between infrastructure and utilization intensity during the early, middle, and late stages of urbanization are not clear. The trajectory of development and coupling within the urbanization process is crucial for understanding issues such as urban over-saturation and urban shrinkage. Using Hegang in Northeastern China as an example, we utilized high-resolution remote sensing data, examined the construction intensity of urban land use, analyzed the degree of coupling with utilization efficiency, and clarified the dynamic evolution of the binary relationship system between development and coupling. Results show that Hegang’s construction intensity has seen a continuous rise from 1992 to 2000, with a 200.06% increase over 28 years, while its coupling with utilization efficiency has experienced a significant drop in the 21st century, suggesting a persistent decline in the utilization of buildings and a notable urban shrinkage phenomenon. Considering development status and coupling degree, we delineate a characteristic urbanization state curve for Hegang, reflecting its progression through stages of “Underdeveloped, Highly coupled,” to “Underdeveloped, Weakly coupled”, and finally to “Highly developed, Weakly coupled”, offering insights into its urban development path. This research not only establishes a foundational data groundwork for future land-use planning in Hegang but also presents a replicable template for urbanization path analysis in other cities, contributing to a broader understanding of urban development dynamics.

2019odp -- A massive oxygen-rich Type Ib supernova

Stripped envelope (SE) supernovae are explosions of stars that have somehow lost most of their outer envelopes. We present the discovery and analyse the observations of the supernova 2019odp (a.k.a. ZTF19abqwtfu) covering epochs within days of the explosion to late nebular phases at 360\,d post-explosion. Our observations include an extensive set of photometric observations and low- to medium-resolution spectroscopic observations, both covering the complete observable time range. We analysed the data using analytic models for the recombination cooling emission of the early excess emission and the diffusion of the peak light curve. We expanded on existing methods to derive oxygen mass estimates from nebular phase spectroscopy, and briefly discuss progenitor models based on this analysis. Our spectroscopic observations confirm the presence of He in the supernova ejecta and we thus (re)classify SN 2019odp as a supernova . From the pseudo-bolometric light curve, we estimate a high ejecta mass of $M_ ej 4 - 7 M_ The high ejecta mass, large nebular O I Ca II $ line flux ratio ($1.2 - 1.9$), and an oxygen mass above $ 0.5\, M_ point towards a progenitor with a pre-explosion mass higher than $18\,M_ Whereas a majority of analysed SE supernovae in the literature seem to have low ejecta masses, indicating stripping in a binary star system, SN 2019odp instead has parameters that are consistent with an origin in a single massive star. The compact nature of the progenitor ($ 10\,R_ suggests that a Wolf-Rayet star is the progenitor.

AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system

With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT\,2021hdr, whose optical light curve used to be consistent with a classic Seyfert 1 nucleus, which was also confirmed by its optical spectrum and high-energy properties. From late 2021, AT\,2021hdr started to present sudden brightening episodes in the form of oscillating peaks in the Zwicky Transient Facility (ZTF) alert stream, and the same shape is observed in X-rays and UV from Swift data. The oscillations occur every sim 60-90 days with amplitudes of sim 0.2 mag in the g and r bands. Very Long Baseline Array (VLBA) observations show no radio emission at milliarcseconds scale. It is argued that these findings are inconsistent with a standard tidal disruption event (TDE), a binary supermassive black hole (BSMBH), or a changing-look active galactic nucleus (AGN); neither does this object resemble previous observed AGN flares, and disk or jet instabilities are an unlikely scenario. Here, we propose that the behavior of AT\,2021hdr might be due to the tidal disruption of a gas cloud by a BSMBH. In this scenario, we estimate that the putative binary has a separation of sim 0.83 mpc and would merge in sim 7times 10$^4$ years. This galaxy is located at 9 kpc from a companion galaxy, and in this work we report this merger for the first time. The oscillations are not related to the companion galaxy.

Millisecond pulsars phenomenology under the light of graph theory

We compute and apply the minimum spanning tree (MST) of the binary millisecond pulsar population, and discuss aspects of the known phenomenology of these systems in this context. We find that the MST effectively separates different classes of spider pulsars ---eclipsing radio pulsars in tight binary systems with a companion of either sim 0.1–0.8 M$_ (redbacks) or $ M$_ in mass (black widows)--- into distinct branches. The MST also separates black widows (BWs) in globular clusters from those found in the field and groups other pulsar classes of interest, including transitional millisecond pulsars (tMSPs). Using the MST and a defined ranking for similarity, we identify possible candidates likely to belong to these pulsar classes. In particular, based on this approach, we propose the BW classification of J1300+1240, J1630+3550, J1317-0157, J1221-0633, J1627+3219, J1737-0314A, and J1701-3006F, discuss that of J1908+2105, and analyze J1723-2837, J1431-4715, and J1902-5105 as possible transitional systems. We introduce an algorithm that quickly locates where new pulsars fall within the MST and use this to examine the positions of the tMSP IGR J18245-2452 (PSR J1824-2452I), the tMSP candidate 3FGL J1544.6-1125, and the accreting millisecond X-ray pulsar SAX J1808.4-3658. Assessing the positions of these sources in the MST ---assuming a range for their unknown variables (e.g., the spin period derivative of PSR J1824-2452I)---, we can effectively narrow down the parameter space necessary for searching for and determining key pulsar parameters through targeted observations.

The formation of multiples in small-N subclusters

Abstract We explore the relative percentages of binary systems and higher-order multiples that are formed by pure stellar dynamics, within a small subcluster of N stars. The subcluster is intended to represent the fragmentation products of a single isolated core, after most of the residual gas of the natal core has dispersed. Initially the stars have random positions, and masses drawn from a log-normal distribution. For low-mass cores spawning multiple systems with Sun-like primaries, the best fit to the observed percentages of singles, binaries, triples and higher-order systems is obtained if a typical core spawns on average between N = 4.3 and 5.2 stars, specifically a distribution of N with mean $\mu _{_{N}}\sim 4.8$ and standard deviation $\sigma _{_N}\sim 2.4$. This fit is obtained when $\sim 50\%$ of the subcluster’s internal kinetic energy is invested in ordered rotation and $\sim 50\%$ in isotropic Maxwellian velocities. There is little dependence on other factors, for example mass segregation or the rotation law. Whilst such high values of N are at variance with the lower values often quoted (i.e. N = 1 or 2), very similar values (N = 4.3 ± 0.4 and N = 4.5 ± 1.9) have been derived previously by completely independent routes, and seem inescapable when the observed distribution of multiplicities is taken into account.

XMM‐Newton Observations of the Peculiar Be X‐Ray Binary A0538‐66

ABSTRACTA0538‐66 is a neutron star/Be x‐ray binary located in the Large Magellanic Cloud and, since its discovery in the 70s, it showed a peculiar behavior that makes it a unique object in the high‐mass x‐ray binaries scene: the extremely eccentric orbit (), the short spin period of the neutron star ( ms), the episodes of super‐Eddington accretion. These characteristics contribute to a remarkable bursting activity that lasts from minutes to hours and increases the flux by a factor . In 2018, A0538‐66 was observed by XMM‐Newton in a particularly active state, characterized by a forest of short bursts lasting s each. In this contribution, we present a reanalysis of these observations. The timing analysis allowed us to distinguish between the epochs of direct accretion and propeller state that do not correlate with the orbital position of the neutron star. The spectral analysis revealed that during the accretion regime, three components (a soft one, a hard one, and a ‐keV emission line) equally contribute to the overall emission, while the propeller regime is characterized by a single soft component. We discuss these findings in the context of spherical and disk accretion regimes, highlighting the similarities and differences with other x‐ray binary systems.

Evaluating and improving the predictive accuracy of mixing enthalpies and volumes in disordered alloys from universal pretrained machine learning potentials

The advent of machine learning in materials science opens the way for exciting and ambitious simulations of large systems and long time scales with the accuracy of calculations. Recently, several pretrained universal machine learned interatomic potentials (UPMLIPs) have been published, i.e., potentials distributed with a single set of weights trained to target systems across a very wide range of chemistries and atomic arrangements. These potentials raise the hope of reducing the computational cost and methodological complexity of performing simulations compared to models that require for-purpose training. However, the application of these models needs critical evaluation to assess their usability across material types and properties. In this work, we investigate the application of the following UPMLIPs: MACE, CHGNET, and M3GNET to the context of alloy theory. We calculate the mixing enthalpies and volumes of 21 binary alloy systems and compare the results with DFT calculations to assess the performance of these potentials over different properties and types of materials. We find that the small relative energies necessary to correctly predict mixing energies are generally not reproduced by these methods with sufficient accuracy to describe correct mixing behaviors. However, the performance can be significantly improved by supplementing the training data with relevant training data. The potentials can also be used to partially accelerate these calculations by replacing the structural relaxation step. Published by the American Physical Society 2024

Rational Pathways to Ordered Multianion Chalcogenides Using Retrosynthetic Crystal Chemistry.

Mixed-anion chalcogenides make up a versatile class of materials with properties that can be fine-tuned for specific applications. While chalcogen anions (Q = S, Se, or Te) tend to form solid solutions in simple binary systems, ordering does occur in structures that have more than one unique anion site. Here, we use crystallographic analysis and hard-soft acid-base principles to predict the Wyckoff positions that secondary chalcogens will occupy in a range of single-anion hosts. The analysis serves as a guide for generating ordered sulfoselenide, selenotelluride, and sulfotelluride products in a predictable manner. The study focuses on ternary and quaternary systems with varying compositional and structural features, with an emphasis on 3D CsCu5Q3 (P42/mnm) and 2D NaCuZrQ3 (Pnma) crystal systems. The samples were prepared by using high-temperature solid-state methods and structurally characterized by using single-crystal X-ray diffraction. Ordering in the mixed-anion products is attributed to the size and bonding variance across the chalcogen series. The degree of ordering varies according to the distinctiveness of the local chemistry at the anion sites and additionally the specific combination of chalcogens employed in the reaction. Additionally, we find that mixed-chalcogen products can adopt phases that are distinct from their single-anion end members, including KCuZrTe2S (P21/m), where an alternate arrangement of polyhedral building blocks maximizes favorable bonding interactions. Density-functional theory calculations corroborate the experimental findings and offer additional insights into the ordering trends. We anticipate that the reverse-engineering approach, which is inspired by the retrosynthetic analyses used in molecular chemistry, will help accelerate the discovery and understanding of heteroanionic phenomena.

Surface Activity of Hydrophobized Modified Starch Hydrolysates in Mixed Systems

The manuscript presents research focusing on the adsorption and emulsion properties of starch hydrolysates modified through acetylation, oxidation, and cross-linking. The techniques used in this study included measurements of equilibrium surface tension (du Noüy ring) dynamic surface tension (drop shape analysis), and the preparation and evaluation of emulsion stability (TURBISCAN). The surface activity of the acetylated starch hydrolysates is affected by the degree of acetylation. The acetylated starch 0.02Ac-H exhibited higher surface activity than the more highly substituted derivative 0.1Ac-H. Furthermore, it was shown that the surface activity of the components increased as the acetylated oxidized starch underwent hydrolysis. The fractions collected after 180 min using a membrane with a low separation capability (8 kDa) revealed the highest capacity for reducing surface tension. In binary systems consisting of starch derivatives and surfactants, synergistic effects in reducing surface tension were particularly noticeable in systems containing ionic surfactants. The addition of a cationic surfactant to the modified starch hydrolysate solution (1:6 mol/mol) resulted in a significantly more efficient saturation of the air/water interface. This study demonstrated that emulsions stabilized with modified starch hydrolysates remained stable over time, even when these hydrolysates constituted up to 60% of the emulsifier mixture.

Analytical study of the merging rate of low-mass intermediate-mass black holes in preparation for the future Einstein Telescope

The detection of gravitational wave (GW) signals by Advanced LIGO, Virgo, and KAGRA interferometers opened a new chapter in our understanding of the formation of compact objects. In particular, the detection of GW190521 is observational confirmation of the existence of intermediate-mass black holes (IMBHs); yet more direct observations are needed to better understand the mechanisms behind their formation. In this study, we explore the potential of the next-generation ground-based detector, the Einstein Telescope (ET), to advance our understanding of astrophysics through the detection of GWs emitted by IMBHs. To achieve this, the ET is designed to have improved sensitivity in the low-frequency range of approximately 2-10 Hz, enabling the detection of GWs originating from binary systems containing IMBHs with masses in the range of approximately 10$^2$-10$^5$ $M_ odot We consider black holes (BHs) in the pair-instability form via the hierarchical merger model in galaxies, and approximate the number of events that could be observed by the ET. Our findings indicate that ET could detect a binary black hole (BBH) merger rate of around $2 yr^ $ for BH masses ranging from 10 to 200 M$ odot $, with around 100 $Gpc^ yr^ $ of this rate specifically attributed to BHs in the 100–200 M$ odot $ mass range, which we classify as low-mass IMBHs in this study. This suggests that ET could detect several dozen events similar to GW190521. The exact locations of these BBH mergers are not specified and we count our BH mergers across the entire universe up to a redshift of $z$ approx 2. Observations made with the ET are expected to significantly enhance our comprehension of galactic BH growth, and the existence and characteristics of low-mass IMBHs.

Modeling Spitzer 3.6 and 4.5 μm Eclipse Depths for the Inflated Hot Jupiter in the Evolved Binary System HD 202772

As an inflated hot Jupiter orbiting an early-type primary star in the evolved binary HD 202772 system, HD 202772 A b’s presence invites a study of how such a planet forms and evolves. As a prelude to potential atmospheric characterization with the latest generation of observatories, we present a reduction and analysis of eclipse light-curve observations of HD 202772 A b acquired with the Spitzer Space Telescope using the 3.6 and 4.5 μm channels. We find eclipse depths of 680 ± 68 and 1081−53+54 ppm, respectively, corresponding to dayside effective temperatures of 2130−91+102 and 2611−49+46 K. The corresponding Bond albedos are consistent with the distribution of albedos for hot Jupiters observed with both Spitzer and Transiting Exoplanet Survey Satellite. The heat redistribution efficiencies consistent with the Bond albedo range predicted by one-dimensional atmospheric models in radiative-convective equilibrium are 0.71 ± 0.10 and 0.03−0.02+0.03 , respectively, indicating a weak day–night contrast for the former and a strong contrast for the latter. Given this, and the unique environment in which this planet resides, we recommend follow-up observations with JWST to more precisely constrain its atmospheric composition and structure, as well as its host stellar environment, to elucidate if and how the atmospheres of these close-in giants evolve with host stars in binaries past the main sequence.

Vapour–liquid equilibrium using quantum chemical molecular dynamics simulation and radial distribution function analysis

AbstractInstead of the classical molecular simulation widely implemented for estimating the vapour–liquid equilibrium (VLE), a quantum chemical (QC) molecular dynamics simulation was applied to the VLE estimation in three typical systems that include a deep eutectic solvent (DES) and an ionic liquid (IL). In addition, a radial distribution function (RDF) was derived from the QC simulation to examine the molecular behaviour in the liquid phase. A mean absolute error of 2.72% was obtained from the QC simulation compared to the experimental data. The RDF analysis explains the relative volatility increase of the acetic acid and water binary system with the propyl acetate solvent. This analysis indicated that the DES mixture comprising glycerol and choline chloride facilitated the separation of water and i‐propanol. The interaction between water and ethyl sulphate pair with the help of 1‐ethyl‐3‐methylimidazolium as an IL is stronger than that between ethanol and water, which explains how the IL improves ethanol and water separation in the vapour phase.

Unveiling nodeless unconventional superconductivity proximate to honeycomb-vacancy ordering in the Ir-Sb binary system

Vacancies in solid-state physics are underexplored in materials with strong electron-electron correlations. Recent research on the Ir-Sb binary system revealed an extended buckled-honeycomb vacancy (BHV) order. Superconductivity arises by suppressing BHV ordering through high-pressure growth with excess Ir atoms or Rh substitution, yet the superconducting pairing nature remains unknown. To explore this, we conducted muon spin rotation experiments on Ir1−δSb (synthesized at 5.5 GPa, Tc = 4.2 K) and ambient pressure synthesized optimally Rh-doped Ir1−xRhxSb (x=0.3, Tc = 2.7 K). The exponential temperature dependence of the superfluid density suggests a fully gapped superconducting state exists in both samples. The ratio of Tc to the superfluid density resembles that of unconventional superconductors. A significant increase in the superfluid density in the high-pressure synthesized sample correlates with Tc, indicating that unconventional superconductivity is intrinsic to the Ir-Sb binary system. These findings, along with the dome-shaped phase diagram, highlight IrSb as the first unconventional superconducting parent phase with ordered vacancies, requiring further theoretical investigations.