Binary Systems Research Articles

Detection of extragalactic magnetic massive stars

odot $ leave behind neutron stars and black holes by the end of their evolution. The merging of binary compact remnant systems produces astrophysical transients detectable by gravitational wave observatories. Studies of magnetic fields in massive stars with low metallicities are of particular interest because they provide important information on the role of magnetic fields in the star formation of the early Universe. While several detections of massive Galactic magnetic stars have been reported in the last few decades, the impact of a low-metallicity environment on the occurrence and strength of stellar magnetic fields has not yet been explored. Because of the similarity between Of?p stars in the Magellanic Clouds (MCs) and Galactic magnetic Of?p stars, which possess globally organised magnetic fields, we searched for magnetic fields in Of?p stars in the MCs. Additionally, we observed the massive contact binary Cl$*$ NGC\,346\,SSN7 in the Small Magellanic Cloud to test the theoretical scenario that the origin of magnetic fields involves a merger event or a common envelope evolution. We obtained and analysed measurements of the magnetic field in four massive Of?p stars in the MCs and the binary Cl$*$ NGC\,346\,SSN7 using the ESO/VLT FORS2 spectrograph in spectropolarimetric mode. We detected kilogauss-scale magnetic fields in two Of?p-type stars and in the contact binary Cl$*$ NGC\,346\,SSN7. These results suggest that the impact of low metallicity on the occurrence and strength of magnetic fields in massive stars is low. However, because the explored stellar sample is very small, additional observations of massive stars in the MCs are necessary.

A macroscopic model for predicating stepwise crystalline swelling of montmorillonite

Bentonite, as an optimal buffer material in high-level radioactive waste (HLRW) repository, is usually unsaturated and sensitive to relative humidity (RH) conditions. Accurately modelling unsaturated crystalline swelling of bentonite is crucial for estimating the performance of a geological repository. In this study, we attempt to extend Laird model, a classical model for crystalline swelling, from saturated to unsaturated. For this purpose, a binary system that comprising air phase and water phase is introduced into Laird model, then the concept of effective diabattivity for atmosphere with a certain RH is proposed. On the basis, the net hydration repulsions under various RHs conditions can be determined. To calibrate the effective diavattivity, the oriented montmorillonite (Mt) tactoids is prepared and the RH controlled X-ray diffraction test is carried out. Moreover, a coupling approach of molecular dynamics (MD) simulation and fluctuation–dissipation dielectric theorem is employed to gain interlayer dielectric from dipolar fluctuations, which further improves the model accuracy. The novel model is validated by the experimental results for 3 typical buffer materials, including MX-80, Kunipia and FEBEX bentonites. Comparisons between the predicted and measured basal spacings indicate the proposed model can effectively capture the stepwise nature of crystalline swelling. Besides, the model also provides a quantitative approach to track the evolution of interaction energy during hydration process.

Gas Sensors Based on Nanostructures of Binary and Ternary Oxide Systems

Introduction. Nanomaterials based on binary and multicomponent oxides are of interest for the development of catalysts, photocatalysts, gas sensors, solar cells, as well as in other fields. The most effective methods to produce oxide systems of various compositions are those of chemical co-deposition, as well as two-stage approaches.Aim. To develop sensor nanomaterials based on ZnO, Zn–Fe–O, and Zn–Sn–O ternary oxide nanosystems, as well as to develop methods for assessing their properties.Materials and methods. ZnO and ZnFe2O4 nanopowders were synthesized by chemical coprecipitation, and ZnFe2O4 and Zn2SnO4 nanostructures were produced by modifying ZnO nanowires. The surface chemical composition and microstructure were studied using scanning electron microscopy, backscattered electron diffraction, and Xray photoelectron spectroscopy. The sensor responses of the samples to vapors of organic solvents were analyzed.Results. The response value of zinc oxide and zinc ferrite samples synthesized by chemical coprecipitation was found to be 2–4 orders of magnitude higher than that of modified zinc oxide nanowires. The formation of ternary oxide nanostructures led to an increase in the sensor response of zinc oxide nanowires. This effect can be explained by the formation of adsorption sites of various types during formation of such systems. The samples produced by chemical coprecipitation showed an extremely high sensor response. This may be due to the formation of fractal structures at the percolation threshold.Conclusion. ZnO and ZnFe2O4 oxide nanostructures produced by chemical coprecipitation exhibit a high sensor response to acetone and ethanol vapors. Methods for the formation of multicomponent oxide systems with improved sensor properties compared to the original zinc oxide nanowires were developed. The resultant sensor nanomaterials are promising for use as sensitive layers of gas sensors for detecting organic solvent vapors.

Ternary Polymer Solar Cells: Impact of Non-Fullerene Acceptors on Optical and Morphological Properties

Ternary organic solar cells contain a single three-component photoactive layer with a wide absorption window, achieved without the need for multiple stacking. However, adding a third component into a well-known binary blend can influence the energetics, optical window, charge carrier transport, crystalline order and conversion efficiency. In the form of binary blends, the low-bandgap regioregular polymer donor poly(3-hexylthiophene-2,5-diyl), known as P3HT, is combined with the acceptor PC61BM, an inexpensive fullerene derivative. Two different non-fullerene acceptors (ITIC and eh-IDTBR) are added to this binary blend to form ternary blends. A systematic comparison between binary and ternary systems was carried out as a function of the thermal annealing temperature of organic layers (100 °C and 140 °C). The power conversion efficiency (PCE) is improved due to increased fill factor (FF) and open-circuit voltage (Voc) for thermal-annealed ternary blends at 140 °C. The transport properties of electrons and holes were investigated in binary and ternary blends following a Space-Charge-Limited Current (SCLC) protocol. A favorable balanced hole–electron mobility is obtained through the incorporation of either ITIC or eh-IDTBR. The charge transport behavior is correlated with the bulk heterojunction (BHJ) morphology deduced from atomic force microscopy (AFM), contact water angle (CWA) measurement and 2D grazing-incidence X-ray diffractometry (2D-GIXRD).

EXPRESS: Admission Control in Multi-server Systems under Binary Reward Structure

We study a multi-server queueing system where a customer is satisfied (and generates a unit revenue) if their queueing time is at most a given constant. If the queueing time of the admitted customer exceeds this constant, the customer gets served, but is unsatisfied and generates no revenue. Such queueing systems arise in the context of modeling service systems where excessive delays are of concern. A key challenge is how to design an admission control policy to maximize the number of satisfied customers per unit time in the long run, assuming that we can observe the number of customers in the system at any time. We call this the binary reward structure system and show that a threshold-type admission policy is optimal. The optimal threshold policy has to be computed numerically. Hence we propose a square-root admission policy to approximate the optimal admission control policy, and compare the performance of these two policies. We derive an analytical upper bound on the performance of optimal admission control policy by deriving an optimal admission policy assuming we have full information over the queueing time of the admitted customers. This is equivalent to a queueing system where customers abandon the queue (i.e., leave without service) if their queueing time exceeds the given constant. We demonstrate that the optimal policy that includes customer abandonment, or alternatively, the optimal policy under full information, the optimal threshold policy, and the square-root admission policy, all exhibit identical performance in the asymptotic regions of the parameter space. Our numerical results indicate that the worst optimality gap of the square-root admission policy is within 3.9% of the optimal revenue, and implementing the square-root admission policy in the observable queueing system leads to a revenue loss that is at most 5.6% of the maximum possible revenue rate in the full information system. We also compare the binary reward structure with the more common linear reward structure where the system incurs holding cost per unit queueing time per customer. In addition, we also show that the analysis based on queueing time is applicable to the system time as well.

Predefined‐time tracking control of multiplicative systems

ABSTRACTThis article describes a control approach for obtaining predefined‐time robust tracking in multiplicative systems despite positive, bounded, and unknown multiplicative disturbances. The proposed approach is distinguished by imposing predefined‐time convergence, a topic previously studied in conventional calculus in the context of multiplicative systems. Multiplicative calculus is recognized as a beneficial tool that complements standard calculus by simplifying the modeling and comprehension of numerous processes. Simulations are carried out to illustrate that the given control strategy enforces convergence before a predefined time instant and, while inducing robustness against system uncertainties. The findings of this article pave the way for further research into predefined‐time synchronization of multiplicative oscillator systems, which would bring promising implications for data encryption and secure communication.

Testing an exact diffraction formula with gravitational wave source lensed by a supermassive black hole in binary systems

When it comes to long-wavelength gravitational waves (GWs), diffraction effect becomes significant when these waves are lensed by celestial bodies. Typically, the traditional diffraction integral formula neglects large-angle diffraction, which is often adequate for most of cases. Nonetheless, there are specific scenarios, such as when a GW source is lensed by a supermassive black hole in a binary system, where the lens and source are in close proximity, where large-angle diffraction can play a crucial role. In our prior research, we have introduced an exact, general diffraction integral formula that accounts for large-angle diffraction as well. This paper explores the disparities between this exact diffraction formula and the traditional, approximate one under various special conditions. Our findings indicate that, under specific parameters — such as a lens-source distance of D LS = 0.1 AU and a lens mass of M L = 4 × 106 M ⊙ — the amplification factor for the exact diffraction formula is notably smaller than that of the approximate formula, differing by a factor of approximately rF ≃ 0.806. This difference is substantial enough to be detectable. Furthermore, our study reveals that the proportionality factor rF gradually increases from 0.5 to 1 as D LS increases, and decreases as M L increases. Significant differences between the exact and approximate formulas are observable when D LS ≲ 0.2 AU (assuming M L = 4 × 106 M ⊙) or when M L ≳ 2 × 106 M ⊙ (assuming D LS = 0.1 AU). These findings suggest that there is potential to validate our general diffraction formula through future GW detections.

Gravitational radiation from eccentric binary black hole system in dynamical Chern-Simons gravity

Dynamical Chern-Simons (DCS) gravity, a typical parity-violating gravitational theory, modifies both the generation and propagation of gravitational waves from general relativity (GR). In this work, we derive the gravitational waveform radiated from a binary slowly-rotating black hole system with eccentric orbits under the spin-aligned assumption in the DCS theory. Compared with GR, DCS modification enters the second-order post-Newtonian (2PN) approximation, affecting the spin-spin coupling and monopole-quadrupole coupling of binary motion. This modification produces an extra precession rate of periastron. This effect modulates the scalar and gravitational waveform through a quite low frequency. Additionally, the dissipation of conserved quantities results in the secular evolution of the semimajor axis and the eccentricity of binary orbits. Finally, the frequency-domain waveform is given in the post-circular scheme, requiring the initial eccentricity to be ≲ 0.3. This ready-to-use template will benefit the signal searches and improve the future constraint on DCS theory.

The SPHERE view of the Chamaeleon I star-forming region

Context. The past few years have seen a revolution in the study of circumstellar disks. New instrumentation in the near-infrared and (sub)millimeter regimes have allowed us to routinely spatially resolve disks around young stars of nearby star-forming regions. As a result, we have found that substructures with scales of ~10 au in disks are common. We have also revealed a zoo of different morphologies, sizes, and luminosities that is as complex as the diversity of architectures found in evolved exoplanet systems. Aims. We study disk evolutionary trends as they appear in scattered light observations. Scattered light traces the micron-sized particles at the disk surface that are well coupled to the gas. This means that scattered light observations can be used to trace the distribution of the disk gas and its interaction with embedded perturbers. Methods. We used VLT/SPHERE to observe 20 systems in the Cha I cloud in polarized scattered light in the near-infrared. We combined the scattered light observations with existing literature data on stellar properties and with archival ALMA continuum data to study trends with system age and dust mass. We also connected resolved near-infrared observations with the spectral energy distributions of the systems. Results. In 13 of the 20 systems included in this study we detected resolved scattered light signals from circumstellar dust. For the CR Cha, CT Cha, CV Cha, SY Cha, SZ Cha, and VZ Cha systems we present the first detailed descriptions of the disks in scattered light. The observations found typically smooth or faint disks, often with little substructure, with the notable exceptions of SZ Cha, which shows an extended multiple-ringed disk, and WW Cha, which shows interaction with the cloud environment. New high S/N K-band observations of the HD 97048 system in our survey reveal a significant brightness asymmetry that may point to disk misalignment and subsequent shadowing of outer disk regions, possibly related to the suggested planet candidate in the disk. We resolve for the first time the stellar binary in the CS Cha system. Multiple wavelength observations of the disk around CS Cha have revealed that the system contains small, compact dust grains that may be strongly settled, consistent with numerical studies of circumbinary disks. We find in our sample that there is a strong anti-correlation between the presence of a (close) stellar companion and the detection of circumstellar material with five of our seven nondetections located in binary systems. We also find a correlation between disk mass, as inferred from millimeter observations, and the detection of scattered light signal. Finally, we find a tentative correlation between relative disk-to-star brightness in scattered light and the presence of a dust cavity in the inner (unresolved) disk, as traced by the system spectral energy distribution. At the same time, faint disks in our sample are generally younger than 2 Myr.

Synthesis of Ag/NiFe2O4 doped multiwalled carbon nanotube for antibiotic removal from water

Antibiotics impose severe impacts on humans and the ambient water environment by creating antimicrobial resistance in bacterial pathogens; therefore, there exists an urgent need to develop sustainable and efficient adsorbents for the removal of these contaminants from the water. To this goal, silver/nickel ferrite-doped multiwalled carbon nanotubes (Ag/NiFe2O4 doped MWCNTs) were prepared as functional integrated adsorbent material for antibiotic removal from water. The TEM results showed that Ag/NiFe2O4 species were dispersed on the surface of MWCNTs through the available functional groups on their surface. The introduction of Ag/NiFe2O4 nanocomposite onto the MWCNTs efficiently improved the adsorption capacity for ciprofloxacin. The maximum adsorption capacity is estimated to be 26.45 mg/g. The results indicated a higher adsorptive capacity for the produced ternary sample compared to pristine MWCNTs, Ag/NiFe2O4, or NiFe2O4/MWCNTs binary systems. The adsorption capacity for ciprofloxacin in the samples was evidently dependent on the MWCNTs dose, solution pH, adsorbate dose, and temperature. Ag/NiFe2O4 doped MWCNTs (65 % w/w) were able to remove ∼95 % of ciprofloxacin in the testing solution even after being reclaimed for 4 times following the Langmuir isotherm model in the endothermic manner. Also, the adsorption of CIP by the nanocomposite demonstrates a pseudo-second-order model. These promising results open a pathway for efficient carbon materials to be replaced by conventional adsorbents to remove antibiotics from water.

Discovery of a hot post-AGB star in Galactic globular cluster E3

We report a new hot post-asymptotic giant branch (PAGB) star in the Galactic globular cluster (GC) E3, which is one of the first of the identified PAGB stars in a GC to show a binary signature. The star stands out as the brightest source in E3 in the Astrosat/UVIT images. We confirmed its membership with the cluster E3 using Gaia DR3 kinematics and parallax measurements. We supplemented the photometric observations with radial velocities (RVs) from high-resolution spectroscopic observations at two epochs and with ground- and space-based photometric observations from 0.13 μm to 22 μm. We find that the RVs vary over ∼6 km s−1 between the two epochs. This is an indication of the star being in a binary orbit. A simulation of possible binary systems with the observed RVs suggests a binary period of either 39.12 days or 17.83 days with mass ratio q ≥ 1.0. The [Fe/H] derived using the high-resolution spectra is ∼−0.7 dex, which closely matches the cluster metallicity. The spectroscopic and photometric measurements suggest Teff and logg of the star as 17 500 ± 1000 K and 2.37 ± 0.20 dex, respectively. Various PAGB evolutionary tracks on the Hertzsprung–Russell (H–R) diagram suggest a current mass of the star in the range 0.51–0.55 M⊙. The star is enriched with C and O abundances, showing similar CNO abundances compared to the other PAGB stars in GCs with the evidence of the third dredge-up on the AGB phase.

First Light Curve Analysis of NSVS 8294044, V1023 Her, and V1397 Her Contact Binary Systems

The first photometric light curve investigation of the NSVS 8294044, V1023 Her, and V1397 Her binary systems is presented. We used ground-based observations for the NSVS 8294044 system and Transiting Exoplanet Survey Satellite data for V1023 Her and V1397 Her. The primary and secondary times of minima were extracted from all the data, and, by collecting the literature, a new ephemeris was computed for each system. Linear fits for the O − C diagrams were conducted using the Markov Chain Monte Carlo (MCMC) method. Light curve solutions were performed using the PHysics Of Eclipsing BinariEs Python code and the MCMC approach. The systems were found to be contact binary stars based on the fillout factor and mass ratio. V1023 Her showed the O’Connell effect, and a cold starspot on the secondary component was required for the light curve solution. The absolute parameters of the system were estimated based on an empirical relationship between orbital period and mass. We presented a new T–M equation based on a sample of 428 contact binary systems and found that our three target systems were in good agreement with the fit. The positions of the systems were also depicted on the M–L, M–R, q–L ratio, and M tot–J 0 diagrams in the logarithmic scales.

A systematic investigation of solution and technological parameters for the fabrication and characterization of poly (vinyl alcohol–chitosan electrospun nanofibers

AbstractNanomaterials, particularly nanofibers are demonstrating exceptional potential for medical applications considered as promising systems for the integration of drug molecules, providing an enhancement of drug effectiveness and safety, while reducing drug side effects. Nanofibers based on two polymeric matrices poly(vinyl alcohol) (PVA) and chitosan (CS) have been demonstrated to be safe and promising materials for the drug integration and targeted drug delivery. This article studied the factors influencing on the fabrication and properties of PVA–CS nanofibers, including the impact of solution components on solution structure, rheological properties, electrospinning technology parameters, as well as the structure and thermomechanical properties of the obtained nanofibers have been investigated in details. The increasing of acetic acid concentration has the effect of pH lowering as well as electrical conductivity while heightening its viscosity. The pH, conductivity, and viscosity values of the solution rises as the CS concentration increases. Based on the Hildebrand‐Scatchard solubility theory, calculated Teas diagrams that account intermolecular interactions allow to predict low‐defect nanofibers based on PVA–CS in binary solvent systems with a greater concentration of hydrogen bonds. The optimal solution content and electrospinning parameters were determined. Infrared spectroscopy confirmed that the two polymer materials have a good interaction and the acetic acid was completely separated from the PVA–CS nanofibers. The XRD spectrum reveals that the crystal lattice parameters of the nanofibers change according to the polymer ratio. The polymers ratio also influence on the thermal and tensile properties. Such biosafe polymer materials may be considered as the promising drug delivery systems with the targeted mode of action.

The Hera Radio Science Experiment at Didymos

Hera represents the European Space Agency's inaugural planetary defense space mission and plays a pivotal role in the Asteroid Impact and Deflection Assessment international collaboration with NASA DART mission that performed the first asteroid deflection experiment using the kinetic impactor techniques. With the primary objective of conducting a detailed post-impact survey of the Didymos binary asteroid following the DART impact on its small moon called Dimorphos, Hera aims to comprehensively assess and characterize the feasibility of the kinetic impactor technique in asteroid deflection while conducting an in-depth investigation of the asteroid binary, including its physical and compositional properties as well as the effect of the impact on the surface and shape of Dimorphos. In this work, we describe the Hera radio science experiment, which will allow us to precisely estimate critical parameters, including the mass, which is required to determine the momentum enhancement resulting from the DART impact, mass distribution, rotational states, relative orbits, and dynamics of the asteroids Didymos and Dimorphos. Through a multi-arc covariance analysis, we present the achievable accuracy for these parameters, which consider the full expected asteroid phase and are based on ground radiometric, Hera optical images, and Hera to CubeSats InterSatellite Link radiometric measurements. The expected formal uncertainties for Didymos and Dimorphos GM are better than 0.01% and 0.1%, respectively, while their J2 formal uncertainties are better than 0.1% and 10%, respectively. Regarding their rotational state, the absolute spin pole orientations of the bodies can be recovered to better than 1 degree, and Dimorphos’ spin rate to better than 10-3%. Dimorphos reconstructed relative orbit can be estimated at the sub-m level. Preliminary results, using a higher-fidelity dynamical model of the coupled motion between rotational and orbital dynamics, show uncertainties in the main parameters of interest that are comparable to those in standard radio science models. A first-order estimate of the expected uncertainty in the momentum transfer efficiency from DART's impact, obtainable with Hera, yields a value of about 0.25. This represents a significant improvement compared to current estimates. Overall, the retrieved values meet the Hera radio science requirements and goals, and remain valid under the condition that the system is determined to be in an excited but non-chaotic (or tumbling) state. The Hera radio science experiment will play an integral role in the exploration of the Didymos binary asteroid system and will provide unique scientific measurements, which, when combined with other observables such as optical images, altimetry measurements, and satellite-to-satellite tracking of the CubeSats, will support the mission's overarching goals in planetary defense and the deep understanding of binary asteroids.

Quasinormal Modes in Noncommutative Schwarzschild Black Holes

We investigate the quasinormal modes of a massless scalar field in a Schwarzschild black hole, which is deformed due to noncommutative corrections. We introduce the deformed Schwarzschild black hole solution, which depends on the noncommutative parameter Θ. We then extract the master equation as a Schrödinger-like equation, giving the explicit expression of the effective potential which is modified due to the noncommutative corrections. After that, we solve the master equation numerically. The significance of these results is twofold. Firstly, our results can be related to the detection of gravitational waves by the near future gravitational wave detectors, such as LISA, which will have a significantly increased accuracy. In particular, these observed gravitational waves produced by binary strong gravitational systems have oscillating modes which can provide valuable information. Secondly, our results can serve as an additional tool to test the predictions of GR, as well as to examine the possible detection of this kind of gravitational corrections.

Wide binaries and modified gravity (MOG)

Wide binaries and modified gravity (MOG)

Thermodynamic and spectroscopic investigation of the molecular interactions among vitamin B5, calcium salt, and cyclodextrins in aqueous media

The pharmaceutical industry aims to enhance drug development processes by gaining a deeper understanding of the physiochemical properties of drug molecules. This study provides a comprehensive analysis of the volumetric and compressibility properties of the drug, calcium-D-pantothenate (CDP) in aqueous solutions of cyclodextrins (β-CD/HP-β-CD). By measuring density and speed of sound, we have evaluated various parameters, including apparent molar volume, compressibility, and their corresponding infinite dilution parameters. by measuring density and speed of sound. In addition to this, positive transfer parameters such as ΔtrVs,φo and ΔtrKs,φo of solute provide insights into solute-co-solute and solute–solvent interactions. Also, Hepler’s constant offers valuable information on the structure-breaking characteristics of the studied drug in cyclodextrin medium. The decrease in molar conductance of binary system on addition of cyclodextrin supports our theoretical observation from volumetric and compressibility studies. Positive values of activation energy favours spontaneity and solubilization process. Furthermore, the 1H NMR study demonstrates that the β-CD molecule interacts more strongly with CDP molecules as compared to HP-β-CD.

Supernova Archaeology with X-Ray Binary Winds: The Case of GRO J1655−40

Supernovae are responsible for the elemental enrichment of the galaxy, and some are postulated to leave behind a black hole. In a stellar binary system, the supernova pollutes its companion, and the black hole can accrete back its own debris and emit X-rays. In this sequence of events, which is only poorly understood, winds are ejected and observed through X-ray absorption lines. Measuring abundances of elements in the wind can lead to inferences about the historical explosion and possibly identify the long-gone progenitor of the compact object. Here, we reanalyze the uniquely rich X-ray spectrum of the 2005 outburst of GRO J1655−40. We reconstruct the absorption measure distribution (AMD) of the wind and find that it increases sharply with ionization from H-like O up to H-like Ca and then flattens out. The AMD is then used to measure the relative abundances of 18 different elements. The present abundances are in partial agreement with a previous work with discrepancies mostly for low-Z elements. The overabundance of odd-Z elements hints at a high-metallicity, high-mass (≃25 M ⊙) progenitor. Interestingly, the abundances are different from those measured in the companion atmosphere, indicating that the wind entrains lingering ambient supernova debris. This can be expected since the current total stellar mass of the binary (<10 M ⊙) is much less than the progenitor mass.

Coupled Phase Diagram Study and Thermodynamic Modeling of the Na2O-B2O3-ZnO System

The Phase diagram of ternary Na2O-B2O3-ZnO system was investigated for the first time using the classical equilibration/quenching method and differential thermal analysis followed by the phase analysis using the Electron Probe Micro-Analysis (EPMA) and X-Ray Diffraction (XRD). The isothermal phase diagrams of this ternary system at 900, 1000 and 1100oC were determined, and the melting temperatures of two ternary compounds were investigated using Differential Thermal Analysis (DTA). The thermodynamic modeling of ternary Na2O-B2O3-ZnO system was carried out based on the present ternary phase diagram data and the optimized model parameters of binary systems. Thermodynamic models with optimized model parameters were used to predict the phase diagram of the ternary Na2O-B2O3-ZnO system.

Runaway OB Stars in the Small Magellanic Cloud. III. Updated Kinematics and Insights into Dynamical versus Supernova Ejections

We use the kinematics of field OB stars to estimate the frequencies of runaway stars generated by the dynamical ejection scenario (DES), the binary supernova scenario (BSS), and the combined two-step mechanism. We update the proper motions for field OB and OBe stars in the Small Magellanic Cloud (SMC) using Gaia DR3. Our sample now contains 336 stars from the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC, and we update our algorithm to calculate more accurate velocities compared to those obtained previously from DR2. We find a decrease in median velocity from 39 to 29 km s−1, implying that the proper motions from our previous work were systematically overestimated. We present the velocity distribution for OBe stars and quantitatively compare it to those of noncompact binaries and high-mass X-ray binaries. We confirm that OBe stars appear to be dominated by the BSS and are likely post-SN binary systems, further supporting the mass-transfer model to explain the origin of their emission-line disks. In contrast, normal OB stars may show a bimodal velocity distribution, which may be expected from different processes that occur with dynamical ejections. The kinematics of fast-rotating OB stars are similar to those of normal OB stars rather than OBe stars, suggesting that the origin of their high vrsini is different from that of OBe stars. We update our model parameters describing the kinematic origins of the SMC field population, still confirming that for runaway stars, the DES mechanism dominates, and two-step ejections seem comparable in frequency to pure BSS ejections.