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The Au-In binary system has been reviewed and the thermodynamic description was re-assessed using the CALPHAD method with aid of first-principles calculations based on density functional theory (DFT). The predicted enthalpy of formation of all stable and hypothesized intermetallics in the Au-In binary system were used to support the optimization. Compared with the previous assessment of this system, a part of thermodynamic models of the intermediate phases were renewed by considering their atomic positions in the lattice, e.g. the model of Au $$_3$$ In $$_2$$ ( $$\Psi$$ ) phase was revised as (Au) $$_{0.2}$$ (Au, In) $$_{0.6}$$ (In) $$_{0.2}$$ , Au $$_9$$ In $$_4$$ ( $$\gamma$$ ) phase was considered as an intermetallic, modeling as (Au) $$_{0.6923}$$ (In) $$_{0.3077}$$ , and Au $$_{10}$$ In $$_3$$ ( $$\beta '$$ ) phase was corrected numerically as (Au) $$_{0.769}$$ (In) $$_{0.231}$$ . The calculated phase diagram agrees well the experimental phase equilibrium data in the literature and the resulting thermodynamic properties are more reasonable. By the coupling of the phase diagram data and experimental together with predicted thermodynamic data, a set of thermodynamic parameters describing all phases in the Au-In system was obtained.

The Kepler satellite has observed more than eight hundred close binary systems [1], for which it was possible to measure not only the orbital periods, but also the rotation velocities of the stars. It turned out that many stars in close binaries are not synchronized, i.e., the rotation period of the star is not exactly equal to the orbital period. The paper considers two models that can explain the asynchrony of stars: either due to the differential rotation of the star or due to the nonzero eccentricity of the binary system. A numerical simulation of the star’s evolution in a binary system is carried out, considering the inverse effect of a companion on the star, depending on the orbital parameters, and it is shown that a close binary system can be not only in a synchronized, but also in an unsynchronized state during the lifetime of the star on the main sequence. This model is applied to the KIC 8736245 system.

We report the discovery of a rare close binary system, SMSS J160639.78-100010.7, comprised of a magnetic white dwarf with a field of about 30 MG and a brown dwarf. We measured an orbital period of 92 min which is consistent with the photometric period. Minimum and maximum light occur at the orbital quadratures Phi=0.25 and 0.75, respectively, and cannot be caused by reflection on the brown dwarf, but, instead, by a spot on the synchronously rotating magnetic white dwarf. The brown dwarf does not fill its Roche lobe and the system may be in a low-accretion state or, more likely, in a detached state following episodes of mass transfer. SMSS J160639.78-100010.7 is the nearest known magnetic white dwarf plus brown dwarf system., Comment: Accepted for publication in MNRAS Letters

The examination of long-term (1979-2020) photometric observations of SS433 enabled us to discover a non-zero orbital eccentricity of $e=0.05\pm 0.01.$ We have also found evidence for a secular increase in the orbital period at a rate of $\dot P_\mathrm{b}=(1.0\pm0.3)\times10^{-7}$ s s$^{-1}$. The binary orbital period increase rate makes it possible to improve the estimate of the binary mass ratio $q=M_\mathrm{X}/M_\mathrm{V}>0.8$, where $M_\mathrm{X}$ and $M_\mathrm{V}$ are the masses of the relativistic object and the optical star, respectively. For an optical star mass of 10${\rm M}_\odot$, the mass of the relativistic object (a black hole) is $M_\mathrm{X}>8{\rm M}_\odot$. A neutron star in SS433 is reliably excluded because in that case the orbital period should decrease, in contradiction to observations. The derived value of $\dot P_\mathrm{b}$ sets a lower limit on the mass-loss rate in the Jeans mode from the binary system $\gtrsim 7\times 10^{-6} {\rm M}_\odot\mathrm{yr}^{-1}$. The discovered orbital ellipticity of SS433 is consistent with the model of the slaved accretion disc tracing the precession of the misaligned optical star's rotational axis., 5 pages, 4 figures + Appendix. Accepted for publication in MNRAS Letters

HL Draconis (HL Dra) is an oscillating eclipsing binary with an orbital period of 0.944276 d. By analysing the light curves observed with the Transiting Exoplanet Survey Satellite (TESS), it has been detected that HL Dra is an Algol-like binary system with a mass ratio of 0.361, where the radius filling factor (=r/RL) of the primary and secondary component is $87\, {{\ \rm per\ cent}}$ and $98\, {{\ \rm per\ cent}}$, respectively. The secondary component is almost filling its critical Roche lobe, but not entirely. The absolute parameters of the component are estimated in this paper. Both the variable O’Connell effect and the existence of superflares indicate that the secondary should have strong magnetic activities. It is discovered that the O − C curve shows a sinusoidal variation with a period of 129.88 yr. This cyclic change might be caused by the effects of the light travel time as a result of the presence of a cool red dwarf third body. The correlations between the changes of the O − C diagrams and the variable O’Connell effect during TESS observations might be caused by the magnetic activity of the secondary (i.e. the Applegate mechanism). After removal of the binary model, a total of 252 pulsation frequencies are detected from the high-precision photometric data of TESS, including 28 multiplets of tidally split frequencies. We identify two radial modes, 21 non-radial p-modes and three non-radial f-modes from the possible independent frequencies. All of these features reveal that HL Dra is a very interesting system for further investigations of binary formation and evolution, and for tidal interactions on stellar pulsations and on magnetic activities.

We derive the second-order post-Newtonian solution for the quasi-Keplerian motion of a nonspinning compact binary system in the Wagoner–Will–Epstein–Haugan representation. This adds a new formulation to the literature in which the motion solution has been formulated in the Brumberg–Damour–Deruelle–Schafer representation and the osculating-element parametrization. We also show that the orbital period and the pericenter precession in the Wagoner–Will–Epstein–Haugan representation are identical to those in the other formulations.

We performed the first light curve analysis of GW Leo and a new ephemeris is obtained for QT Boo. The light curve investigation also yields that the system GW Leo is a contact W UMa eclipsing binary with a photometric mass ratio of q = 0.44 ± 0.03, a fillout factor of f = 59.6%, and an inclination of 50.77° ± 0.09°. Due to the O’Connell effect which is known as asymmetries in the light curves’ maxima, a cold spot is employed along with the solution. The photometric and physical parameters of GW Leo were determined (e.g., Mh = 1.373 ± 0.024, Mc = 0.604 ± 0.027, Rh = 1.261 ± 0.041, Rc = 0.909 ± 0.039, and a( $${{R}_{ \odot }}$$ ) = 2.553 ± 0.004). According to the light curve solution results, we suggest that GW Leo is an A-type W UMa binary system. We also calculate the distance of GW Leo from the distance modulus formula as 483.5 ± 41 pc, which is in a good agreement to the quantity measured by the Gaia EDR3 using the binary systems' parallax. Moreover, the positions of their components on the H–R diagram are represented.

Abstract The variations in the orbital periods of the eclipsing binary systems XZ Per and BO Vul have been studied. It has been shown that the variations in the orbital period of the eclipsing binary XZ Per are equally well represented as a superposition of the secular decrease and cyclic variations or as a sum of two cyclic variations. In the first case, the monotonic component can be a consequence of the loss of angular momentum by the system due to magnetic braking, while cyclic variations can be explained by the presence of a third body in the system or by the magnetic activity of the secondary component with a convective shell. In the second case, it is possible to assume the presence of two additional bodies in the system, or to attribute one of the period oscillations to the light-time effect, and the other to the magnetic activity of the secondary component. The variations in the orbital period of the eclipsing binary system BO Vul can be represented as a superposition of the secular decrease and cyclic variations. The observed cyclic variations in the period can occur due to the presence of a third body in the system or due to the magnetic activity of the secondary component with a convective shell.

We consider a new mechanism for the removal of the angular momentum from an X-ray binary system and the change in its orbital period - the mass loss in the form of a wind from an accretion disc. Both observations and models predict powerful winds from discs in X-ray transients. We have obtained an analytical estimate for the increase in the orbital period of a binary system with a wind from the disc during an outburst, and quantitative estimates are given for the systems XTE J1118+480, A0620-00 and GRS 1124-68. Resulting rate of period grow is of order of the observed rates of secular decrease in the period. We also compare the predicted rate of change in the period of a binary system due to the flow of matter into the disc and outflow from the second Lagrange point with the observations. It is concluded that the above mechanisms cannot explain the observed secular decrease in the period of the three X-ray Novae, and it is necessary to consider a circumbinary disc that drains the binary's angular momentum., 10 pages, 7 figures, 2 tables, accepted for publication in Astronomy Letters

Many stars are in binaries or higher-order multiple stellar systems. Although in recent years a large number of binaries have been proven to host exoplanets, how planet formation proceeds in multiple stellar systems has not been studied much yet from the theoretical standpoint. In this paper we focus on the evolution of the dust grains in planet-forming discs in binaries. We take into account the dynamics of gas and dust in discs around each component of a binary system under the hypothesis that the evolution of the circumprimary and the circumsecondary discs is independent. It is known from previous studies that the secular evolution of the gas in binary discs is hastened due to the tidal interactions with their hosting stars. Here we prove that binarity affects dust dynamics too, possibly in a more dramatic way than the gas. In particular, the presence of a stellar companion significantly reduces the amount of solids retained in binary discs because of a faster, more efficient radial drift, ultimately shortening their lifetime. We prove that how rapidly discs disperse depends both on the binary separation, with discs in wider binaries living longer, and on the disc viscosity. Although the less-viscous discs lose high amounts of solids in the earliest stages of their evolution, they are dissipated slowly, while those with higher viscosities show an opposite behaviour. The faster radial migration of dust in binary discs has a striking impact on planet formation, which seems to be inhibited in this hostile environment, unless other disc substructures halt radial drift further in. We conclude that if planetesimal formation were viable in binary discs, this process would take place on very short time scales., 18 pages, 11 figures; accepted for publication in MNRAS

Two scenarios were investigated for predicting binary gas adsorption equilibria when the single gas isotherms of one component is described by the three process Langmuir (TPL) model and the single gas isotherms of the other component is described by either the dual process Langmuir (DPL) or single process Langmuir (SPL) model. For the TPL–SPL and TPL–DPL models, 7 and 12 different correlations of energetic (free energy) site matching respectively exist. For these complex systems, perfect positive (PP) means the free energies of the sites of the two components align in some way from high to low, while perfect negative (PN) means they misalign in some way with high free energy sites for one component aligning with low free energy sites for the other component. Other variations of PP and PN exist where the free energies correlate in some way with the free energy of the site of one of the components distributed among two or more sites of the other component, and uncorrelated exit where the free energies do not correlate but possibly still have some site distribution. A consistent set of single and binary isotherms for CO2 and N2 on 13X zeolite were used to explore all 19 correlations. CO2 fitted well only to the TPL single gas model and N2 fitted equally well to either the DPL or SPL single gas model. Only 3 of the 12 cases for the TPL–DPL model and 2 of the 7 cases for the TPL–SPL model exhibited reasonable predictions of the experimental results; the remaining 14 cases failed. The predictions for CO2 for both models were very good for all 19 cases; but, some of the predictions for N2 were so overpredicted, they were not even close to reality. The simpler site matching correlations fared better than the more complex ones, such as those with the sites of N2 distributed over two or more sites of CO2. For this CO2–N2-13X binary system, PP site matching correlations provided the best predictions, with the high and low free energy sites of N2 decidedly interacting with the high and medium free energy sites of CO2 with the low free energy site of CO2 unoccupied by N2.

A kinetic impact occurs when an asteroid is moving. The impact may be caused by other small celestial body or an artificial object. Ejecta is produced from an impact. Dynamics of ejecta near a binary system which contains an ellipsoid and a sphere is analyzed. A phase diagram which comes from numerical simulation is shown in this work. The phase diagram shows a clear structure. Some special trajectories are also shown, which indicates a potential source of asteroid orbiting objects.

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1 m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4 m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work.

The results of optical spectroscopic monitoring observations of a young binary system, Z CMa, are presented in this study. Z CMa consists of a Herbig Be star and an FU Orionis object, and it shows irregular light variation in the quiescent phase and exploding brightening in the outburst phase. Medium-resolution spectra were obtained on 21 nights between 2015 and 2019 using the Nayuta telescope in Japan. We also used five high-resolution spectra, obtained between 2008 and 2011, with the Keck Telescope. During the outburst phase, the intensity of the He I absorption line increased with an increase in the luminosity of the system. Because the He I absorption line is a characteristic feature of an early-type star, we considered that the outbursts were caused by the Herbig Be star. The equivalent widths of the [O I] line decreased with an increase in the luminosity of the system. We claim steady mass loss at the rate of The intensities of the Hα and Fe II emission lines did not change during the outbursts. However, the line intensities increased with an increase in the luminosity of the system in the quiescent phase. We consider that those lines are attributed to the FU Orionis object and the light variations in the quiescent phase were caused by the FU Orionis object.

In 2015 a radial velocity monitoring campaign was started in order to redetermine and/or constrain the orbital solutions of spectroscopic binary systems. The observations were carried out at the University Observatory Jena with the \'Echelle spectrograph FLECHAS. The results from the main part of our target sample are already published. For the final target of this campaign, $\theta$ Cep, we can now present an orbital solution based on a homogeneously covered radial velocity curve. The period of this single-lined spectroscopic binary turns out to be significantly larger and the orbit is much more eccentric compared to the given values in the 9th Catalogue of Spectroscopic Binary Orbits., Comment: 8 pages, 2 figures, 4 tables, accepted for publication in AN

The intermediate mass Herbig Ae star V1787 Ori is a member of the L1641 star-forming region in the Orion A molecular cloud. We report the detection of an M-type companion to V1787 Ori at a projected separation of 6.66" (corresponding to 2577 au), from the analysis of VLT/NACO adaptive optics $K_s$-band image. Using astrometric data from Gaia DR2, we show that V1787 Ori A and B share similar distance ($d$ $\sim$ 387 pc) and proper motion, indicating that they are physically associated. We estimate the spectral type of V1787 Ori B to be M5 $\pm$ 2 from color--spectral type calibration tables and template matching using SpeX spectral library. By fitting PARSEC models in the Pan-STARRS color-magnitude diagram, we find that V1787 Ori B has an age of 8.1$^{+1.7}_{-1.5}$ Myr and a mass of 0.39$^{+0.02}_{-0.05}$ $M_\odot$. We show that V1787 Ori is a pre-main sequence wide binary system with a mass ratio of 0.23. Such a low mass ratio system is rarely identified in Herbig Ae/Be binary systems. We conclude this work with a discussion on possible mechanisms for the formation of V1787 Ori wide binary system., 10 pages,3 tables, 5 figures, accepted for publication in MNRAS

The results of 14-year photometric monitoring of the contact close binary system (CBS) W UMa-type AM Leo are presented. Low-amplitude cyclic variations in brightness with a period of $$7.6 \pm 0.3$$ years, not associated with the phenomena of eclipses and tidal deformations of the components, as well as low-amplitude cyclic variations of the CBS period with practically the same value of the oscillation period, were found. It is concluded that the mechanism generating such oscillations may be the process of changing the magnetic field of the convective shells of the components. Based on the detected decrease in the depths of both minima of the light curves and the change in their relative values, it was concluded that the system is currently transiting from the W-subtype class to the A-subtype class. The values of seven new values of the moments of minima are given.

The variations in the orbital period of the eclipsing binary system V505 Sgr, which is a part of the visual binary system CHR 90, have been analyzed. It has been shown that the variations in the period can be represented as a superposition of the secular decrease in the period at a rate of 2.97 × 10–7 days/year and the light-time effect with a period of 72.8 years. The secular decrease in the period can be explained by the loss of angular momentum due to magnetic braking on the secondary component of a late spectral type. The light-time effect is explained by the presence of a third body in the system, which was discovered from both spectral and speckle interferometric observations.

The phoebe code was used to analyse the Kepler light-curve and to estimate the physical and geometrical parameters of a rare pulsating binary system, KIC 3858884. The analysis indicated that the system is composed of two detached and very similar main-sequence A-type stars, in a highly eccentric orbit with e = 0.47. After disentangling the binarity effect, the residual data were subjected to Fourier frequency decomposition using period04 software. The resulting frequency spectrum consists of two moderately high-amplitude nearby frequencies, F1 = 7.232199 d−1 and $F2=7.472889\, \mathrm{d}^{-1}$, which were attributed to δ Scuti-type pulsations. In addition, 18 frequencies were identified that were exact harmonics of the orbital frequency $f_{\rm orb}= 0.038533\, \mathrm{d}^{-1}$, and also 53 anharmonics. However, it was found that many of these anharmonic frequencies coupled together non-linearly to give harmonic modes of pulsation. Furthermore, some existing theoretical models of the tidal oscillations were numerically verified in general binary systems through estimations of various modal characteristics, for example mode quantum numbers ${n, l, m,}$ energies Ei, threshold energies Ei,th, damping rates γi, growth rates Γi and stability criteria, etc. The evolution of the stars in the binary system was compared with some similar single pulsating stars on the Hertzsprung–Russell diagram and it was concluded that the evolution of a single star is more rapid. Finally, the observed rate of apsidal line displacement was estimated through eclipse timing variation analysis as Uobs = 74745.2 ± 2566 yr. This was compared with the theoretically calculated rate of the line of apsides motion, UTheo = 73588 ± 2298 yr, and found to be in good agreement within errors, hence verifying general relativity theory once again.

The variations in the orbital period of the eclipsing binary system Z Per have been analyzed. It has been shown that the variations in the period can be represented as a superposition of the secular decrease in the period at a rate of 1.61 × 10–6 days/year and its three cyclic variations with periods of 22.6, 37.9, and 62.4 years. Z Per is most likely a quadruple system with periods of additional orbits equal to 22.6 and 62.4 years, while cyclic oscillations with a period of 37.9 years are a consequence of the magnetic activity of the secondary component. The secular decrease in the orbital period of the eclipsing binary system can be caused by the loss of angular momentum due to magnetic braking.

The properties of a model based on the analogy between binary stratifying liquid mixtures and coupled self-oscillating systems is studied. In this paper, an expression representing a curve mapping in the phase diagram of a binary system is derived. The mapping of a boundary curve is presented in the form of the dependence between the ratio of characteristic frequencies assigned to pure components and the mixture concentration. In the framework of this model, the temperature dependence of the squared ratio of frequencies $$({\nu}_{a}/{\nu}_{b})^{2}$$ is also determined. One important aspect of this model is that the temperature-dependent characteristic frequencies $$\nu_{a}$$ and $$\nu_{b}$$ reflect the properties of pure components (instead of solutions). The problem is posed of investigating the physical aspects of the model proposed in this paper in more detail. In the present study, it has been shown that the use of Pade approximants makes it possible to determine the character of the temperature dependence of each characteristic frequency separately on the basis of the temperature dependence derived by linking to experimental data for the ratio $$({\nu}_{a}/{\nu}_{b})^{2}$$ .

RY Sct is a unique massive binary star system in a short transitional evolutionary phase. It is an eclipsing binary where both stars have overfilled their Roche cavities, so that the system is in an “overcontact” state. It is surrounded by a young circumstellar nebula. The binary is regarded as a rare progenitor of a type WR+OB system. RY Sct is close to the Eddington luminosity limit, so that radiative pressure plays an important role in mass loss. At least one of the components of the close binary may be associated with a rare class of LBV stars or the so-called S Doradus variables. We have calculated the orbital elements using the old photometric data of Zakirov and Kumsiashvili and new spectral data, together with an analysis of HST observations. A model was examined according to which the components of RY Sct are in an overcontact state and fill their Roche cavities. The brighter primary component transfers mass to the more massive but less bright secondary. The binary system is surrounded by a common envelope. As initial parameters we, chose a mass ratio q = 4.42 and orbital period P = 11d.12471, and used an orbital inclination of i = 75.6°.

Compact orbiting binaries like the black hole binary system observed in GW150914 carry large amount of orbital angular momentum. The post-ringdown compact object formed after merger of such a binary configuration has only spin angular momentum, and this results in a large orbital angular momentum excess. One significant possibility is that the gravitational waves generated by the system carry away this excess orbital angular momentum. An estimate of this excess is made. Arguing that plane gravitational waves cannot possibly carry any orbital angular momentum, a case is made in this paper for gravitational wave beams carrying orbital angular momentum, akin to optical beams. Restricting to certain specific beam-configurations, we predict that such beams may produce a new type of strain, in addition to the longitudinal strains measured at aLIGO for GW150914 and GW170817. Current constraints on post-ringdown spins, derived within the planewave approximation of gravitational waves, therefore stand to improve. The minimal modification that might be needed on a laser-interferometer detector (like aLIGO or VIRGO) to detect such additional strains is also briefly discussed., Comment: 8 pages, 4 figures Version to appear in EPJC

This paper presents the first detection of Shapiro delay from the binary millisecond pulsar PSR J1811–2405. We report a 11σ measurement of the orthometric amplitude, h3 = 6.8(6) × 10−7, and a 16σ measurement of the orthometric ratio, ς = 0.81(5). Given the relatively high orbital inclination, i = 79(2)°, of this binary system, we obtain constraints on the companion mass of $m_{\rm {c}}=0.31^{+0.08 }_{ -0.06}\, \mathrm{M}_{\odot }$. The pulsar mass is currently less well constrained, with a value of $2.0^{+0.8 }_{ -0.5}\, \mathrm{M}_{\odot }$. The companion mass and the orbital period are in agreement with the prediction made by previous numerical calculations of the evolution of compact binary systems. From a study of the polarization, we find that the orbital inclination angle is ∼100° and that PSR J1811–2405 is an orthogonal rotator. In addition, the μs-level timing precision together with its narrow profile makes PSR J1811–2405 a good candidate for inclusion in the pulsar timing arrays being used to detect nHz gravitational waves.

The evolution of close binary cosmic objects in the mass-asymmetry coordinate is considered. Conditions for the formation of stable symmetric binary stars and galaxies are analyzed. The role of symmetrization of an asymmetric binary system in the transformation of the potential energy into the internal energy and in the release of a large amount of energy is explained.

In the literature, no detailed description is reported about how to detect if a miscibility gap exists in terms of interaction parameters analytically. In this work, a method to determine the likelihood of the presence of a miscibility gap in a binary substitutional solution phase is proposed in terms of interaction parameters. The range of the last interaction parameter along with the former parameters is analyzed for a set of self-consistent parameters associated with the miscibility gap in assessment process. Furthermore, we deduce the first and second derivatives of Gibbs energy with respect to composition for a phase described with a sublattice model in a binary system. The Al-Zn and Al-In phase diagrams are computed by using a home-made code to verify the efficiency of these techniques. The method to detect the miscibility gap in terms of interaction parameters can be generalized to sublattice models. At last, a system of equations is developed to efficiently compute the Gibbs energy curve of a phase described with a sublattice model.

37th International Cosmic Ray Conference, ICRC 2021, Berlin, Germany, 15 Jul 2021 - 22 Jul 2021; Proceedings of Science 395, 1136 (2022). doi:10.22323/1.395.1136 special issue: "37th International Cosmic Ray Conference : ICRC2021 : 12-23 July 2021 : Berlin, Germany - Online / Editorial Board: Alexander Kappes, Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany ; Bianca Keilhauer, Karlsruhe Institute of Technology, Institute for Astroparticle Physics (IAP)", Published by SISSA, Trieste

The properties of low-mass neutron stars with rigid rotation are considered. The possible evolution paths of such stars in a close binary system with mass transfer are calculated. The properties of the gamma-ray burst GRB 170817A interpreted in terms of the stripping model, a natural ingredient of which is the explosion of a low-mass neutron star - a binary component, are briefly discussed., Comment: 16 pages, 3 figs, 1 table

Atmospheric modeling and dynamical analysis of the components of the visually close binary system (VCBS) HD6009 were used to estimate their individual physical and geometrical parameters. Model atmospheres were constructed using a grid of Kurucz solar metalicity blanketed models and used to compute the individual synthetic spectral energy distribution (SED) for each component separately. These SEDs were combined together to compute the entire SED for the system from the net luminosities of the components $a$ and $b$ located at a distance $d$ from the Earth. %The entire observational SED of the system was used as a reference for the comparison with the synthetic ones. We used the feedback modified parameters and iteration method to get the best fit between synthetic and observational entire SEDs. The physical and geometrical parameters of the system's components were derived as: $T_{\rm eff}^{a} =5625\pm75$\,K, $T_{\rm eff}^{b} =5575\pm75$\,K, log $g_{a}=3.75\pm0.25$, log $g_{b}=3.75\pm0.25$, $R_{a}=2.75\pm0.30 R_\odot$, $R_{b}=2.65\pm0.30 R_\odot$, $M_v^{a}= 2\fm80\pm0.30$, $M_v^{b}=2\fm93\pm0.30$, $M_a= 1.42\pm0.15 M_{\odot}$, $M_b=1.40\pm0.15 M_{\odot}$, $L_a=6.80\pm0.75 L_\odot$, $L_b=6.09\pm0.75 L_\odot$ and $\pi=14.43$mas dynamical parallax. The system is shown to be consist of G6 IV primary and G6 IV secondary components., Comment: 7 pages, 4 figures, 7 Tables. arXiv admin note: text overlap with arXiv:1311.5721, arXiv:1204.4589

I present a numerical fit to the peak harmonic gravitational wave frequency emitted by an eccentric binary system in the post-Newtonian approximation. This fit significantly improves upon a previous commonly-used fit in population synthesis studies, in particular for eccentricities $\lesssim 0.8$., Research Notes of the American Astronomical Society (RNAAS). 3 pages, 1 figure

Stable compounds in the V-N binary system are systematically investigated and four new phases are found: $Pbam\text{\ensuremath{-}}{\mathrm{V}}_{5}{\mathrm{N}}_{2}, Pnma\text{\ensuremath{-}}{\mathrm{V}}_{2}\mathrm{N}, P\overline{3}m1\text{\ensuremath{-}}{\mathrm{V}}_{2}{\mathrm{N}}_{3}$, and $I4/mcm\text{\ensuremath{-}}{\mathrm{VN}}_{2}$. All the predicted high-pressure vanadium nitrides are dynamically stable at ambient pressure. Moreover, the thermodynamic stability of vanadium nitrides in the temperature range of 0--1500 K at different pressures (0, 20, 40, 60, and 120 GPa) was also evaluated within the harmonic approximation. The sequence of phases of ${\mathrm{V}}_{2}\mathrm{N}$ under pressure is $\ensuremath{\varepsilon}{\text{-Fe}}_{2}\text{N}\phantom{\rule{0.16em}{0ex}}\text{type}\ensuremath{\rightarrow}\ensuremath{\zeta}{\text{-Fe}}_{2}\text{N}\phantom{\rule{0.16em}{0ex}}\text{type}\ensuremath{\rightarrow}{\text{Fe}}_{2}\text{C}\phantom{\rule{0.16em}{0ex}}\text{type}\ensuremath{\rightarrow}Pnma{\text{-V}}_{2}\text{N}$. In addition, relative stability and lattice dynamics properties of several vanadium mononitrides are systematically calculated and discussed. Structural features, mechanical properties, electronic structures, and chemical bonding of all the V-N compounds are analyzed at 0 GPa. Among these vanadium nitrides, WC-type VN has the highest Vickers hardness ($\ensuremath{\sim}37\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$) and superior fracture toughness (4.3--6.1 MPa ${\mathrm{m}}^{1/2}$), which mainly originate from its strong V-N bonding as well as its strong three-dimensional V-N covalent bond network. The configuration of the strong and short N-N covalent bonds enables the new phase $I4/mcm\text{\ensuremath{-}}{\mathrm{VN}}_{2}$ to exhibit good mechanical properties. Our results also reveal that the formation of a strong covalent-bond network topology in a crystal is a fundamental principle for designing a hard or superhard structure.

The theory of substellar evolution predicts that there is a sharp mass boundary between lithium and non-lithium brown dwarfs, not far below the substellar-mass limit. The imprint of thermonuclear burning is carved on the surface lithium abundance of substellar-mass objects during the first few hundred million years of their evolution, leading to a sharp boundary between lithium and non-lithium brown dwarfs, so-called, the lithium test. New optical spectroscopic observations of the binaries DENIS+J063001.4-184014 and DENIS+J225210.7-173013 obtained using the 10.4-m Gran Telescopio de Canarias are reported here. They allow us to re-determine their combined optical spectral types (M9.5 and L6.5, respectively) and to search for the presence of the LiI resonance doublet. The non detection of the LiI feature in the combined spectrum of DENIS\,J063001.4$-$184014AB is converted into estimates for the depletion of lithium in the individual components of this binary system. In DENIS\,J225210.7$-$173013AB we report the detection of a weak LiI feature which we tentatively ascribe as arising from the contribution of the T3.5-type secondary. Combining our results with data for seven other brown dwarf binaries in the literature treated in a self-consistent way, we confirm that there is indeed a sharp transition in mass for lithium depletion in brown dwarfs, as expected from theoretical calculations. We estimate such mass boundary is observationally located at 51.48$^{+0.22}_{-4.00}$ $M_\mathrm{Jup}$, which is lower than the theoretical determinations., 12 pages, 6 figures, accepted for publication in MNRAS

YY Eri, the short-period binary system, is a W UMa type of the eclipsing binary system. This study using a 0.7-meter telescope with CCD photometric system in B V and R filters. It was observed at the Regional Observatory for the Public, Chachoengsao, Thailand on December 5, 2018, UT. The MaxIm DL software was used to analyzed the images photometry to produce the light curve. The Wilson-Devinney technique was computed the synthetic light curve that prefer to the physical properties of the YY Eri. The results show that the effective temperature of the primary and secondary star was 5533 and 5598 K, respectively. The inclination is 81.450 and the mass ratio is 0.55. The degree of contact was calculated as 16.64%

A significant fraction of the most massive stars move through space with a high velocity. One of the possible physical explanations is that a supernova in a compact binary system results in a high recoil velocity of the system. If the system remains bound, it can be subsequently observed as a spectroscopic binary (SB1), a high-mass X-ray binary, a compact binary, and finally a gravitational-wave event. If such a system is traced back to its parent cluster, binary evolution models can be tested in great detail. The Gaia proper motions and parallaxes are used to demonstrate that the high-mass X-ray binary HD153919/4U 1700-37 originates from NGC6231, the nucleus of the OB association Sco OB1. The O supergiant and its compact companion, of which the physical nature (a neutron star or a black hole) is unknown, move with a space velocity of 63 km/s with respect to NGC6231. The kinematical age of the system is 2.2 Myr. The parallaxes and accurate proper motions in Gaia DR2 were used to perform a membership analysis of NGC 6231. The distance to NGC6231 is 1.63 kpc. Isochrone fitting results in an age of 4.7 Myr. With the identification of NGC6231 as the parent cluster, the upper limit on the age of the progenitor of 4U1700-37 at the moment of the supernova explosion is 3.0 Myr. With these constraints, the evolutionary history of the system can be reconstructed with an initial mass of the progenitor of the compact object >60 Msun. Given its current high space velocity and the derived evolutionary history, the compact object in the system is more likely to have received a large natal kick, which suggests that it is more likely a neutron star than a black hole. HD153919/4U1700-37 might be a prototype in the Milky Way for the progenitor of gravitational wave events such as GW190412, 17 pages, A&A in press

We present observations (with NAO Rozhen and AS Vidojevica telescopes) of the AM Canum Venaticorum (AM CVn) type binary star CR Bootis (CR Boo) in the UBV bands. The data were obtained in two nights in July 2019, when the V band brightness was in the range of 16.1-17.0 mag. In both nights, a variability for a period of $25 (\pm 1)$ min and amplitude of about 0.2 magnitudes was visible. These brightness variations are most likely indications of "humps". During our observational time, they appear for a period similar to the CR Boo orbital period. A possible reason of their origin is the phase rotation of the bright spot, placed in the contact point of the infalling matter and the outer disc edge. We estimated some of the parameters of the binary system, on the base of the observational data., 8 pages, 2 figures

Supernova Ia are bright explosive events that can be used to estimate cosmological distances, allowing us to study the expansion of the Universe. They are understood to result from a thermonuclear detonation in a white dwarf that formed from the exhausted core of a star more massive than the Sun. However, the possible progenitor channels leading to an explosion are a long-standing debate, limiting the precision and accuracy of supernova Ia as distance indicators. Here we present HD265435, a binary system with an orbital period of less than a hundred minutes, consisting of a white dwarf and a hot subdwarf -- a stripped core-helium burning star. The total mass of the system is 1.65+/-0.25 solar-masses, exceeding the Chandrasekhar limit (the maximum mass of a stable white dwarf). The system will merge due to gravitational wave emission in 70 million years, likely triggering a supernova Ia event. We use this detection to place constraints on the contribution of hot subdwarf-white dwarf binaries to supernova Ia progenitors., Preprint of an article published in Nature Astronomy. The final authenticated version is available online at: https://doi.org/10.1038/s41550-021-01413-0

We present the orbital solution of a peculiar double-lined spectroscopic and eclipsing binary system, 2M17091769+3127589. This solution was obtained by a simultaneous fit of both APOGEE radial velocities and TESS and ASAS-SN light curves to determine masses and radii. This system consists of an $M=0.256^{+0.010}_{-0.006}$ $M_\odot$, $R=3.961^{+0.049}_{-0.032}$ $R_{\odot}$ red giant and a hotter $M=1.518 ^{+0.057}_{-0.031}$ $M_\odot$, $R=2.608^{+0.034}_{-0.321}$ $R_{\odot}$ subgiant. Modelling with the MESA evolutionary codes indicates that the system likely formed 5.26 Gyrs ago, with a $M=1.2$ $M_\odot$ primary that is now the system's red giant and a $M=1.11$ $M_\odot$ secondary that is now a more massive subgiant. Due to Roche-lobe overflow as the primary ascends the red giant branch, the more evolved "primary" (i.e., originally the more massive star of the pair) is now only one-sixth as massive as the "secondary". Such a difference between the initial and the current mass ratio is one of the most extreme detected so far. Evolutionary modelling suggests the system is still engaged in mass transfer, at a rate of $\dot{M} \sim 10^{-9}$ $M_\odot$ yr$^{-1}$, and it provides an example of a less evolved precursor to some of the systems that consist of white dwarfs and blue stragglers., Accepted to AJ; 12 pages, 8 figures

We report our analyses of the multi-epoch (2015-2017) ALMA archival data of the Class II binary system XZ Tau at Bands 3, 4 and 6. The millimeter dust continuum images show compact, unresolved (r, Comment: 18 pages, 11 figures, ApJ accepted for publication

AST3-1 is the second-generation optical photometric telescope at Dome A in Antarctica. In this study, photometric solutions of three eclipsing binaries comprising AST19571, AST21541, and AST38503 were determined for the first time using the light curves obtained with AST3-1. The light curves for the three binaries in the Galactic disk field were analyzed with the Wilson–Devinney method. We found that AST19571 and AST21541 are intermediate-contact binary systems with fill-out factors of f = 39.9 ( ± 5.4 ) % and 36.4( ± 4.7) %, respectively, and their mass ratios were determined as q = 0.275 ( ± 0.0034 ) and 0.25( ± 0.0024). AST38503 was shown to be a deep-contact binary system with a degree of contact of f = 66 ( ± 33 ) % and a mass ratio of q = 0.314 ( ± 0.03 ) . Some light minimum times were derived for the three contact binary stars. The results showed that the period of AST19571 is increasing at a rate of d p / d t = + 4.71 × 10 − 7 . This increase in the period could be explained by mass transfer between the components. The absolute parameters were estimated for the components of the three binaries.

UV Psc is a typical RS CVn type system undergoing dynamic chromosphere activity. We performed photometric observations of the system in 2015 and secured new BVR light curves showing well-defined photometric waves. In this paper, we analyzed the light curves using Wilson-Devinney binary code and investigated the orbital period of the system. The combination of our light curve synthesis with the spectroscopic solution developed by previous investigators yielded the absolute parameters as: M1 = 1.104 ± 0.042 Mⵙ, R1 = 1.165 ± 0.025 Rⵙ, and L1 = 1.361 ± 0.041 Lⵙ for the primary star, and M2 = 0.809 ± 0.082 Mⵙ, R2 = 0.858 ± 0.018 Rⵙ, and L2 = 0.339 ± 0.010 Lⵙ for the secondary star. The eclipse timing diagram for accurate CCD and photoelectric timings showed that the orbital period may vary either in a downward parabolic manner or a quasi-sinusoidal pattern. If the latter is adopted as a probable pattern for the period change, a more plausible account for the cyclic variation may be the light time effect caused by a circumbinary object rather than an Applegate-mechanism occurring via variable surface magnetic field strengths.

By means of the CALPHAD (CALculation of PHAse Diagrams) technique, the holmium–gallium binary system was critically assessed. The thermodynamic parameters involved in the excess term of the Gibbs energy phases are optimized based on all the experimental data available in the literature. The Ho–Ga system contains five intermetallic compounds: $${\text{HoGa}}_{6} ,\,{\text{HoGa}}_{3} ,\,{\text{HoGa}}_{2} ,\,{\text{HoGa}}\,{\text{and}}\,{\text{Ho}}_{ 5} {\text{Ga}}_{3}$$, which are all treated as stoichiometric phases. The term $${}_{ }^{\text{exe}} G$$ of the Gibbs energy of the liquid phase is described, using the Redlich–Kister, Kaptay equations and the association solution model. The primary phases $$\alpha {\text{Ho}}$$ (Hcp) and Ga (orthorhombic) are treated as pure stoichiometric phases. The phase diagram and model parameters were derived from a thermodynamic optimization. More experimental work on this system may be needed to confirm our results.

The binary star Par 1802 in the Orion Nebula presents an interesting puzzle in the field of stellar dynamics and evolution. Binary systems such as Par 1802 are thought to form from the same natal material and thus the stellar members are expected to have very similar physical attributes. However, Par 1802's stars have significantly different temperatures despite their identical (within $3\%$) masses of about $0.39$ solar mass. The leading proof-of-concept idea is that a third companion gravitationally induced the two stars to orbit closer than their Roche-limit, which facilitated heating through tidal effects. Here we expand on this idea and study the three-body dynamical evolution of such a system, including tidal and pre-main-sequence evolution. We also include tidal heating and mass transfer at the onset of Roche-limit Crossing. We show, as a proof-of-concept, that mass transfer combined with tidal heating can naturally explain the observed temperature discrepancy. We also predict the orbital configuration of the possible tertiary companion. Finally we suggest that the dynamical evolution of such a system has pervasive consequences. We expect an abundance of systems to undergo mass transfer during their pre-main-sequence time, which can cause temperature differences., Comment: 10 pages, 8 figures, accepted to MNRAS

Recent observations have revealed that protoplanetary discs often exhibit cavities and azimuthal asymmetries such as dust traps and clumps. The presence of a stellar binary system in the inner disc regions has been proposed to explain the formation of these structures. Here, we study the dust and gas dynamics in circumbinary discs around eccentric and inclined binaries. This is done through two-fluid simulations of circumbinary discs, considering different values of the binary eccentricity and inclination. We find that two kinds of dust structures can form in the disc: a single horseshoe-shaped clump, on top of a similar gaseous over-density; or numerous clumps, distributed along the inner disc rim. The latter features form through the complex interplay between the dust particles and the gaseous spirals caused by the binary. All these clumps survive between one and several tens of orbital periods at the feature location. We show that their evolution strongly depends on the gas-dust coupling and the binary parameters. Interestingly, these asymmetric features could in principle be used to infer or constrain the orbital parameters of a stellar companion - potentially unseen - inside the inner disc cavity. Finally, we apply our findings to the disc around AB Aurigae., 12 pages, 13 figures, accepted for publication in MNRAS

Two methodologies were developed to predict adsorption equilibria of a binary system when one of the components is described by the dual-process Langmuir (DPL) model and the other component is described by either the single process Langmuir (SPL) or linear isotherm (LI) model. Energetic site matching with the DPL–SPL model considered perfect positive (PP), perfect negative (PN) and unselective (US) correlations, and that with the DPL–LI model considered PP and PN correlations. A consistent set of single and binary isotherms for O2 and N2 on 5A zeolite were used to successfully demonstrate these concepts. For the DPL–SPL binary system, PP meant O2 adsorbed only on the N2 low energy site, PN meant O2 adsorbed only on the N2 high energy site, and US meant O2 adsorbed on both sites with the ratio of its saturation capacity on each site the same as that for N2. For this case, the PP model predicted the binary data well and correctly predicted that O2 only adsorbed on the low energy site of N2; the PN model predicted the data poorly and US was close but not as good as PP. The binary predictions from the DPL–SPL model that require only single component information to obtain the single component DPL and SPL parameters were nearly as good as those obtained from a non-predictive formulation similar to the US correlation but that utilized all the single and binary data to obtain the single component DPL and SPL parameters. For the DPL–LI binary system, with O2 having an affinity for only one site, PN meant O2 interacted solely with the high energy site of N2 and PP meant O2 interacted solely with the low energy site of N2; and because O2 exhibited a linear isotherm (i.e., the Henry’s law constants from the SPL parameters), it did not affect the adsorption of N2 on its sites, but N2 did affect the adsorption of O2 on its sites. For this case, the PP model predicted the binary data well and correctly predicted that O2 did not affect the adsorption of N2, but that N2 did affect the adsorption of O2 on the low energy site of N2; the PN model predicted the data poorly.

We present the results of spectral observations of the Herbig Ae/Be star HD179218. We discovered a wave-like variation in the parameters of the Hα line emission component with a typical time scale of about 40 days. The observed wave is characterized by a significant decrease in the measured line parameters, with conspicuous branches of increasing and decreasing parameters. Simultaneously, additional blue and red emission and absorption components appear and disappear in the Hα line profile during the moment of minimum. The observed variations in the spectrum of the star may be explained by the existence of polar winds and accretion, or by assuming that the star is a binary system.

NSVS 10441882 is a newly discovered eclipsing binary system with strong magnetic activity and an orbital period of ∼ 0.5166 days. In order to study this eclipsing binary system, we analyzed its first four-color (BVRcIc) light curves. The observed light curves were asymmetric, so we used the 2013 version of the Wilson–Devinney (W–D) program with cool star-spots to analyze these data. We discovered that NSVS 10441882 is a detached total eclipsing binary system with an orbit inclination of 85°.34 ± 0.07 and a mass ratio of q = 0.94 ± 0.03. Based on the CCD times of the light minima according to our observations and those reported previously, the orbital period changes of NSVS 10441882 were studied using the traditional O–C method for the first time. The O–C diagram of the target exhibited a cyclic oscillation with a period of 16.7 ± 0.20 years and an amplitude of 0.00349 ± 0.00029 days, probably due to the presence of an unseen third body. If we assume that the total mass of NSVS 10441882 is 1.3M⊙ (according to our calculated results for the average color index and mass ratio), then the mass of the third body is no less than 0.12 ± 0.01 M⊙. Moreover, the orbital evolution of the central system will be accelerated due to the presence of this additional component.