Search

The discovery in 1962 of the compact source Sco X-1, the first X-ray source located outside the Solar System, marked a new ("golden") era in the study of close binary systems (CBSs). Soon after, accreting neutron stars and first black hole candidates in CBSs were discovered. The ability to "weigh" neutron stars and black holes in CBSs made it possible to distinguish accreting black holes from neutron stars. The theory of accretion onto relativistic objects in CBSs has been developed, as well as the theory of the evolution of CBSs with mass exchange up to the latest stages, including binary black holes and neutron stars. CBSs have become the cutting edge of astrophysics. Subsequent observations of gravitation waves and observations with the EHT intercontinental radio interferometer with an angular resolution of ~10–5 arcsec made it possible to finally prove the existence of black holes in the Universe. Thus, the modern triumph of black holes has largely been due to the development of the science of CBSs. This paper is based on a presentation made in the astrophysical memorial seminar "Novelties in Understanding the Evolution of Binary Stars", dedicated to the 90th anniversary of Professor M.A. Svechnikov. [ABSTRACT FROM AUTHOR]

Eccentricity of wide binaries is difficult to measure due to their long orbital periods. With Gaia 's high-precision astrometric measurements, eccentricity of a wide binary can be constrained by the angle between the separation vector and the relative velocity vector (the v - r angle). In this paper, by using the v - r angles of wide binaries in Gaia Early Data Release 3, we develop a Bayesian approach to measure the eccentricity distribution as a function of binary separations. Furthermore, we infer the eccentricities of individual wide binaries and make them publicly available. Our results show that the eccentricity distribution of wide binaries at 102 AU is close to uniform and becomes superthermal at >103 AU, suggesting two formation mechanisms dominating at different separation regimes. The close binary formation, most likely disc fragmentation, results in a uniform eccentricity distribution at <102 AU. The wide binary formation that leads to highly eccentric wide binaries at >103 AU may be turbulent fragmentation and/or the dynamical unfolding of compact triples. With Gaia , measuring eccentricities is now possible for a large number of wide binaries, opening a new window to understanding binary formation and evolution. [ABSTRACT FROM AUTHOR]

We revisit the eccentric neutron star (NS)â€"white dwarf (WD) binary model for the periodic activity of fast radio burst (FRB) sources, by including the effects of gravitational-wave (GW) radiation. In this model, the WD fills its Roche lobe at the periastron and mass transfer occurs from the WD to the NS. The accreted materials can be fragmented and arrive at the NS episodically, resulting in multiple bursts through curvature radiation. Consequently, the WD may be kicked away owing to the conservation of angular momentum. To initiate the next mass transfer, the WD has to refill its Roche lobe through GW radiation. In this scenario, whether the periodic activity can show up relies on three timescales, i.e., the orbital period P orb, the timescale T GW for the Roche lobe to be refilled, and the time span T frag for all the episodic events corresponding to each mass-transfer process. Only when the two conditions T GW ≲ P orb and T frag < P orb are both satisfied, the periodic activity will manifest itself and the period should be equal to P orb. In this spirit, the periodic activity is more likely to show up for relatively long periods (P orb ≳ several days). Thus, it is reasonable that FRBs 180916 and 121102, the only two sources having been claimed to manifest periodic activity, both correspond to relatively long periods. [ABSTRACT FROM AUTHOR]

R-mode oscillations in a rotating star produce characteristic signatures in a Fourier amplitude spectrum at frequencies related with the rotation frequency, which can be, in turn, used to obtain the surface rotation rate of the star. Some binary stars observed by Kepler indicate the presence of r modes that are probably excited by the tidal effect. In this paper, we have obtained stellar rotation periods in 20 eccentric (heartbeat) binaries with r-mode signatures. The majority of the rotation periods are found to be comparable to pseudo-synchronous periods, in which the angular velocity of rotation is similar to the angular orbital motion of the companion at periastron. In particular, for the heartbeat stars with orbital periods longer than about 8 d, all but one agree with pseudo-synchronous rotation. In contrast to a previous investigation by Zimmerman et al. our result supports the pseudo-synchronisation theory developed by Hut. [ABSTRACT FROM AUTHOR]

We present an analysis of a newly discovered 2+1 + 1 quadruple system with TESS containing an unresolved eclipsing binary (EB) as part of TIC 121088960 and a close neighbour TIC 121088959. The EB consists of two very low-mass M dwarfs in a highly eccentric (e  = 0.709) short-period (P  = 3.043 58 d) orbit. Given the large pixel size of TESS and the small separation (3 |${_{.}^{\prime\prime}}$| 9) between TIC 121088959 and TIC 121088960 we used light centroid analysis of the difference image between in-eclipse and out-of-eclipse data to show that the EB likely resides in TIC 121088960, but contributes only ∼10 per cent of its light. Radial velocity data were acquired with iSHELL at NASA's Infrared Facility and the Coudé spectrograph at the McDonald 2.7-m telescope. For both images, the measured RVs showed no variation over the 11 d observational baseline, and the RV difference between the two images was 8 ± 0.3 km s−1. The similar distances and proper motions of the two images indicate that TIC 121088959 and TIC 121088960 are a gravitationally bound pair. Gaia's large RUWE and astrometric_excess_noise parameters for TIC 121088960, further indicate that this image is the likely host of the unresolved EB and is itself a triple star. We carried out an SED analysis and calculated stellar masses for the four stars, all of which are in the M dwarf regime: 0.19 M⊙ and 0.14 M⊙ for the EB stars and 0.43 M⊙ and 0.39 M⊙ for the brighter visible stars, respectively. Lastly, numerical simulations show that the orbital period of the inner triple is likely the range 1–50 yr. [ABSTRACT FROM AUTHOR]

Eccentricity has emerged as a potentially useful tool for helping to identify the origin of black hole mergers. However, eccentric templates can be computationally very expensive owing to the large number of harmonics, making statistical analyses to distinguish formation channels very challenging. We outline a method for estimating the signal-to-noise ratio (S/N) for inspiraling binaries at lower frequencies such as those proposed for LISA and DECIGO. Our approximation can be useful more generally for any quasi-periodic sources. We argue that surprisingly, the S/N evaluated at or near the peak frequency (of the power) is well approximated by using a constant-noise curve, even if in reality the noise strain has power-law dependence. We furthermore improve this initial estimate over our previous calculation to allow for frequency dependence in the noise to expand the range of eccentricity and frequency over which our approximation applies. We show how to apply this method to get an answer accurate to within a factor of 2 over almost the entire projected observable frequency range. We emphasize this method is not a replacement for detailed signal processing. The utility lies chiefly in identifying theoretically useful discriminators among different populations and providing fairly accurate estimates for how well they should work. This approximation can furthermore be useful for narrowing down parameter ranges in a computationally economical way when events are observed. We furthermore show a distinctive way to identify events with extremely high eccentricity where the signal is enhanced relative to naive expectations on the high-frequency end. [ABSTRACT FROM AUTHOR]

The search for special and rare celestial objects has always played an important role in astronomy. Cataclysmic Variables (CVs) are special and rare binary systems with accretion disks. Most CVs are in the quiescent period, and their spectra have the emission lines of Balmer series, HeI, and HeII. A few CVs in the outburst period have the absorption lines of Balmer series. Owing to the scarcity of numbers, expanding the spectral data of CVs is of positive significance for studying the formation of accretion disks and the evolution of binary star system models. At present, the research for astronomical spectra has entered the era of Big Data. The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) has produced more than tens of millions of spectral data. the latest released LAMOST-DR7 includes 10.6 million low-resolution spectral data in 4926 sky regions, providing ideal data support for searching CV candidates. To process and analyze the massive amounts of spectral data, this study employed the Light Gradient Boosting Machine (LightGBM) algorithm, which is based on the ensemble tree model to automatically conduct the search in LAMOST-DR7. Finally, 225 CV candidates were found and four new CV candidates were verified by SIMBAD and published catalogs. This study also built the Gradient Boosting Decision Tree (GBDT), Adaptive Boosting (AdaBoost), and eXtreme Gradient Boosting (XGBoost) models and used Accuracy, Precision, Recall, the F1-score, and the ROC curve to compare the four models comprehensively. Experimental results showed that LightGBM is more efficient. The search for CVs based on LightGBM not only enriches the existing CV spectral library, but also provides a reference for the data mining of other rare celestial objects in massive spectral data. [ABSTRACT FROM AUTHOR]

Common envelope evolution (CEE) is believed to be an important stage in the evolution of binary/multiple stellar systems. Following this stage, the CE is thought to be ejected, leaving behind a compact binary (or a merger product). Although extensively studied, the CEE process is still little understood, and although most binaries have non-negligible eccentricity, the effect of initial eccentricity on the CEE has been little explored. Moreover, most studies assume a complete circularization of the orbit by the CE onset, while observationally such eccentricities are detected in many post-CE binaries. Here we use smoothed particle hydro-dynamical simulations to study the evolution of initially eccentric (0 ≤ e ≤ 0.95) CE-systems. We find that initially eccentric binaries only partially circularize. In addition, higher initial eccentricity leads to a higher eccentricity following the end of the inspiral phase, with eccentricities as high as 0.18 in the most eccentric cases, and even higher if the initial pericentre of the orbit is located inside the star (e.g. following a kick into an eccentric orbit, rather than a smooth transition). CEE of more eccentric binaries leads to enhanced dynamical mass-loss of the CE compared with more circular binaries, and depends on the initial closest approach of the binary. We show that our results and the observed eccentricities of post-CE binaries suggest that the typical assumptions of circular orbits following CEE might potentially be revised. We expect post-CE eccentricities to affect the delay time distributions of various transients such as supernovae, gamma-ray bursts, and gravitational-wave sources by up to tens of per cents. [ABSTRACT FROM AUTHOR]

We present the first application of deep learning forecasting for binary neutron stars, neutron starâ€"black hole systems, and binary black hole mergers that span an eccentricity range e ≤ 0.9. We train neural networks that describe these astrophysical populations, and then test their performance by injecting simulated eccentric signals in advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) noise available at the Gravitational Wave Open Science Center to (1) quantify how fast neural networks identify these signals before the binary components merge; (2) quantify how accurately neural networks estimate the time to merger once gravitational waves are identified; and (3) estimate the time-dependent sky localization of these events from early detection to merger. Our findings show that deep learning can identify eccentric signals from a few seconds (for binary black holes) up to tens of seconds (for binary neutron stars) prior to merger. A quantized version of our neural networks achieves 4Ă— reduction in model size, and up to 2.5Ă— inference speedup. These novel algorithms may be used to facilitate time-sensitive multimessenger astrophysics observations of compact binaries in dense stellar environments. [ABSTRACT FROM AUTHOR]

Didymos and Dimorphos are primary and secondary, respectively, asteroids who compose a binary system that make up the set of Near Earth Asteroids (NEAs). They are targets of the Double Asteroid Redirection Test (DART), the first test mission dedicated to study of planetary defense, for which the main goal is to measure the changes caused after the secondary body is hit by a kinect impactor. The present work intends to conduct a study, through numerical integrations, on the dynamics of massless particles distributed in the vicinity of the two bodies. An approximate shape for the primary body was considered as a model of mass concentrations (mascons) and the secondary was considered as a massive point. Our results show the location and size of stable regions, and also their lifetime. [ABSTRACT FROM AUTHOR]

Using the model based on the Regge-like laws, new analytical formulas are obtained for the moment of inertia, the rotation frequency, and the radius of astronomical non-exotic objects (planets, stars, galaxies, and clusters of galaxies). The rotation frequency and moment of inertia of a neutron star and the observable Universe are estimated. The estimates of the average numbers of stars and galaxies in the observable Universe are given. The Darwin instability effect in the binary systems (di-planets, di-stars, and di-galaxies) is also analyzed. [ABSTRACT FROM AUTHOR]

Eclipsing binary stars are rare and extremely valuable astrophysical laboratories that make possible precise determination of fundamental stellar parameters. Investigation of early-type chemically peculiar stars in eclipsing binaries provides important information for understanding the origin and evolutionary context of their anomalous surface chemistry. In this study, we discuss observations of eclipse variability in six mercury–manganese (HgMn) stars monitored by the Transiting Exoplanet Survey Satellite (TESS) satellite. These discoveries double the number of known eclipsing HgMn stars and yield several interesting objects requiring further study. In particular, we confirm eclipses in HD 72208, thereby establishing this object as the longest-period eclipsing HgMn star. Among five other eclipsing binaries, reported here for the first time, HD 36892 and HD 53004 stand out as eccentric systems showing heartbeat variability in addition to eclipses. The latter object has the highest eccentricity among eclipsing HgMn stars and also exhibits tidally induced oscillations. Finally, we find evidence that HD 55776 may be orbited by a white dwarf companion. [ABSTRACT FROM AUTHOR]

Secular evolution of binaries driven by an external (tidal) potential is a classic astrophysical problem. Tidal perturbations can arise due to an external point mass, as in the Lidov–Kozai (LK) theory of hierarchical triples, or due to an extended stellar system (e.g. galaxy or globular cluster) in which the binary resides. For many applications, general-relativistic (GR) apsidal precession is important, and has been accounted for in some LK calculations. Here, we generalize and extend these studies by exploring in detail the effect of GR precession on (quadrupole-level) tidal evolution of binaries orbiting in arbitrary axisymmetric potentials (which includes LK theory as a special case). We study the (doubly averaged) orbital dynamics for arbitrary strengths of GR and binary initial conditions and uncover entirely new phase space morphologies with important implications for the binary orbital evolution. We also explore how GR precession affects secular evolution of binary orbital elements when the binary reaches high eccentricity (e → 1) and delineate several different dynamical regimes. Our results are applicable to a variety of astrophysical systems. In particular, they can be used to understand the high eccentricity behaviour of (cluster) tide-driven compact object mergers – i.e. LIGO/Virgo gravitational wave sources – for which GR effects are crucial. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present a search for gravitational waves from subsolar mass compact-binary mergers that allows for nonnegligible orbital eccentricity. Subsolar mass black holes are a signature of primordial origin black holes, which may be a component of dark matter. To produce binary coalescences, primordial black holes may form close binaries either in the early universe or more recently through dynamical interactions. A signature of dynamical formation would be the observation of noncircularized orbits. We search for black hole mergers where the primary mass is 0.1–7M⊙ and the secondary mass is 0.1–1M⊙. We allow for eccentricity up to ∼0.3 at a dominant-mode gravitational-wave frequency of 10 Hz for binaries with component masses >0.5M⊙. We find no convincing candidates in the public LIGO data from 2015–2017. The two most promising candidates have a false alarm rate of 1 per 3 and 4 yr, respectively, which combined is only a ∼2.4σ deviation from the expected Poisson rate. Given the marginal statistical significance, we place upper limits on the rate of subsolar mass mergers under the assumption of a null observation and compare how these limits may inform the possible dark matter contribution. [ABSTRACT FROM AUTHOR]

Tidal dissipation due to turbulent viscosity in the convective regions of giant stars plays an important role in shaping the orbits of pre-common-envelope systems. Such systems are possible sources of transients and close compact binary systems that will eventually merge and produce detectable gravitational wave signals. Most previous studies of the onset of common envelope episodes have focused on circular orbits and synchronously rotating donor stars under the assumption that tidal dissipation can quickly spin-up the primary and circularize the orbit before the binary reaches Roche lobe overflow (RLO). We test this assumption by coupling numerical models of the post-main-sequence stellar evolution of massive stars with the model for tidal dissipation in convective envelopes developed in Vick & Lai – a tidal model that is accurate even for highly eccentric orbits with small pericentre distances. We find that, in many cases, tidal dissipation does not circularize the orbit before RLO. For a |$10\, {\rm M}_{\odot }$| (⁠|$15\, {\rm M}_{\odot }$|⁠) primary star interacting with a |$1.4\, {\rm M}_{\odot }$| companion, systems with pericentre distances within 3 au (6 au) when the primary leaves the main sequence will retain the initial orbital eccentricity when the primary grows to the Roche radius. Even in systems that tidally circularize before RLO, the donor star may be rotating subsynchronously at the onset of mass transfer. Our results demonstrate that some possible precursors to double neutron star systems are likely eccentric at the Roche radius. The effects of pre-common-envelope eccentricity on the resulting compact binary merit further study. [ABSTRACT FROM AUTHOR]

Due to their small mass, subsolar mass black hole binaries would have to be primordial in origin instead of the result of stellar evolution. Soon after formation in the early universe, primordial black holes can form binaries after decoupling from the cosmic expansion. Alternatively, primordial black holes as dark matter could also form binaries in the late universe due to dynamical encounters and gravitational-wave braking. A significant feature for this channel is the possibility that some sources retain nonzero eccentricity in the LIGO/Virgo band. Assuming all dark matter is primordial black holes with a delta function mass distribution, 1M⊙–1M⊙ binaries formed in this late-universe channel can be detected by Advanced LIGO and Virgo with their design sensitivities at a rate of yr−1, where 12%(3%) of events have eccentricity at a gravitational-wave frequency of 10 Hz, e10 Hz ≥ 0.01(0.1), and nondetection can constrain the binary formation rate within this model. Third generation detectors would be expected to detect subsolar mass eccentric binaries as light as 0.01M⊙ within this channel, if they accounted for the majority of the dark matter. Furthermore, we use simulated gravitational-wave data to study the ability to search for eccentric gravitational-wave signals using a quasi-circular waveform template bank with Advanced LIGO design sensitivity. For a match-filtering targeted search, assuming binaries with a delta function mass of 0.1(1)M⊙ and the eccentricity distribution derived from this late-universe formation channel, 41%(6%) of the signals would be missed compared to the ideal detection rate due to the mismatch in the gravitational-wave signal from eccentricity. [ABSTRACT FROM AUTHOR]

We present a detailed study of KIC 2306740, an eccentric double-lined eclipsing binary system. Kepler satellite data were combined with spectroscopic data obtained with the 4.2 m William Herschel Telescope (WHT). This allowed us to determine precise orbital and physical parameters of this relatively long period (P = 10.ͩ3) and slightly eccentric (e = 0.3) binary system. The physical parameters have been determined to be M1 = 1.194 ± 0.008 M⊙, M2 = 1.078 ± 0.007 M⊙, R1 = 1.682 ± 0.004 R⊙, R2 = 1.226 ± 0.005 R⊙, L1 = 2.8 ± 0.4 L⊙, L2 = 1.8 ± 0.2 L⊙, and orbital separation a = 26.20 ± 0.04 R⊙ through simultaneous solutions of the Kepler light curves and WHT radial velocity data. Binarity effects were extracted from the light curve in order to study intrinsic variations in the residuals. Five significant and more than 100 combination frequencies were detected. We modeled the binary system assuming nonconservative evolution models with the Cambridge stars (twin) code, and we show the evolutionary tracks of the components in the plane, the plane, and the plane for both spin and orbital periods together with eccentricity e and. The model of the nonconservative processes in the code led the system to evolve to the observed system parameters in roughly 5.1 Gyr. [ABSTRACT FROM AUTHOR]

Newtonian Quantum Gravity (NQG) unifies quantum physics with Newton's theory of gravity and calculates the so-called "general relativistic" phenomena more precisely and in a much simpler way than General Relativity, whose complicated theoretical construct is no longer needed. Newton's theory of gravity is less accurate than Albert Einstein's theory of general relativity. Famous examples are the precise predictions of General Relativity at binary pulsars. This is the reason why relativistic physicists claim that there can be no doubt that Einstein's theory of relativity correctly describes our physical reality. With the example of the famous "Hulse-Taylor binary" (also known as PSR 1913 + 16 or PSR B1913 + 16), the author proves that the so-called "general relativistic phenomena" observed at this binary solar system can be calculated without having any knowledge on relativistic physics. According to philosophical and epistemological criteria, this should not be possible, if Einstein's theory of relativity indeed described our physical reality. Einstein obviously merely developed an alternative method to calculate these phenomena without quantum physics. The reason was that in those days quantum physics was not yet generally taken into account. It is not the first time that a lack of knowledge of the underlying physical phenomena has to be compensated by complicated mathematics. Einstein's theory of general relativity indirectly already includes additional quantum physical effects of gravitation. This is the reason why it cannot be possible to unite Einstein's theory of general relativity with quantum physics, unless one uses "mathematical tricks" that make the additional quantum physical effects disappear again in the end. [ABSTRACT FROM AUTHOR]

The determination of the orbital parameters of binaries is an important constituent of fundamental astronomy. It is the only reliable way to determine the stellar mass, which is crucial for the studies of stellar dynamics and evolution. And the orbital parameters can be used to compute the motions of component stars, which could improve the population of reference stars in the bright star catalogue reference frame. However, the previous studies on the determination of binaries' orbital parameters adopted some approximations in the computation of observational quantities. According to the statistical results of hundreds of binaries with bright component stars, it could be found that the approximations in the variation of the tangent plane and the prospective effect of the reference plane have made the deviations of computed observational quantities become larger than the present observational precision (1 mas). In this paper, a new algorithm based on the two-body model and the rigorous relation of solid geometry for computing observational quantities is presented. This new algorithm has been verified by fitting the simulation and actually-observed data. And the fitting results show that the fitted parameters solved by the new algorithm usually have a higher confidence than that solved by the approximate algorithm. Therefore, the new algorithm has certain improvements in the determination of the orbital parameters of binaries, especially, for the wide binaries nearby the solar system. [ABSTRACT FROM AUTHOR]

We report a study of the eclipse timing variation (ETV) of short period (P 1 ≤ 6 d ) eclipsing binaries (EBs) monitored during the photometric survey optical gravitational lensing experiment-IV. From the 425 193 EBs, we selected approximately 80 000 binaries that we found suitable for further examination. Among them, we identified 992 potential hierarchical triple (or multiple) system candidates exhibiting light-travel time effect (LTTE). Besides, we obtained the orbital parameters of these systems and carried out statistical analyses on the properties of these candidates. We found that (i) there is a significant lack of triple systems where the outer period is less than 500 d, (ii) the distribution of the outer eccentricities has a maximum around e 2 ≈ 0.3, and (iii) the outer mass ratio calculated from an estimated minimum mass of the third component is lower than q 2 ∼ 0.5 for the majority of the sample. We also present some systems that deserve special attention: (i) There are four candidates that show double periodic ETV, which we explain by the presence of a fourth companion; (ii) For two systems, the perturbations of the third component are also found to be significant therefore we give a combined dynamical and LTTE ETV solution; and (iii) For one system, the third component is found to be probably in the substellar mass domain. [ABSTRACT FROM AUTHOR]

Highlights • The Corona Borealis/A2142 as a supercluster binary-like system has been revised. • Tidal analysis confirms a balanced gravitational interaction between them. • A peculiar velocity sample supports a flow of the A2142 region towards the CB. • The peculiar velocity sample may be biased by selection effect due to remoteness. • Even if the interaction between them is evident, the true dynamics remain unclear. Abstract The recent hypothesis of a giant supercluster binary-like structure formed by the Corona Borealis and its close companion Abell 2142 (supercluster) belongs to a little known area of investigation as the dynamics of gravitationally interacting galaxy supercluster pairs. From the observational point of view this structure approximates the configuration of a binary-like system in linear orbit interconnected by a huge filamentary structure which, if confirmed, it would be the first case to date observed at z ≥ 0.07. Given the importance to disentangle this issue, a follow-up analysis has been performed on the region constrained by the common envelop of the two superclusters in order to search for new hints to confirm their mutual gravitational interaction. Observational signatures of that interaction have been found mapping the inner peculiar motions where the observed negative peculiar velocities measured within the A2142 (supercluster) region suggest a general matter flow toward the Corona Borealis supercluster. Besides, analyzing the effects on both superclusters due to the mutual impact of the external tidal forces, turns out that their inner dynamics remain unperturbed up to the turnaround radii. Outside, where the binding forces are overlapped by the tidal ones, the outskirts of both superclusters should be unstable and subject to fragmentation. Such a scenario indicates that both superclusters interact with comparable and reciprocal tidal perturbations leaving the whole system in a substantial dynamical equilibrium. The origin of such a dynamical dichotomy would be explained either by a much more massive Corona Borealis supercluster than that estimated in the present work or by a selection effect biasing the small sample of peculiar velocities due to the remoteness of the system worsened by the large uncertainty on their measurements. [ABSTRACT FROM AUTHOR]

Highlights • We analysed the short cadence data taken from Kepler Database to model the flare and spot activities of KIC 11560447. • We detected 226 flares, which were analysed to model and compare with the analogues of the target. • In the analyses, we computed the flare frequencies and derived the OPEA model for the flares. • We also modelled the stellar spot activity occurring on the surface of the target. Abstract Analysing the photometrical data taken from the Kepler Mission Database, the results obtained from both the One Phase Exponential Association model derived for the flare activity and the spot migration on the surface of eclipsing binary system KIC 11560447 are presented. A sinusoidal variation due to the rotation modulation is defined. There are two cool spots separated by about 100° longitudinally. It is seen that the parameters of these spotted areas such as radii, latitudes and longitudes, were varying during observing seasons. Apart from the cool spots, flare activity is also detected on the target, and 226 flares were determined with their parameters. Modelling the distribution of flare equivalent durations versus the flare total times, the Plateau parameter was found to be 1.4114 ± 0.1712 s in the logarithmic scale, while the Half-time value was found to be 2394.03 s. The frequency of flare N 1 , which is the number of flares per an hour in the system, was computed as 0.064454 h − 1 , while the flare-equivalent duration emitting per an hour, N 2 frequency, was found to be 0.000058. [ABSTRACT FROM AUTHOR]

I propose that at the termination of the common envelope evolution (CEE) the companion to the giant star might launch jets that have variable directions and intensities, hence the jets shape the inner zones of the descendant nebula causing it to lose any type of symmetry. This might account for some of the chaotic departures from axisymmetric structures in some planetary nebulae. I base my study on the assumption that at the termination of the CEE the binary interaction forms a circumbinary thick disc that feeds the companion via an accretion disc that launches opposite jets. I consider two processes that might lead to the development of Rayleigh–Taylor instabilities that lead to chaotic accretion flow on to the companion. The chaotic accretion flow leads to a variable accretion disc around the companion, hence to variable jets. In the first process the jets inflate low-density hot bubbles in the inner regions of the envelope. In the second process the inner boundary of the thick circumbinary disc, that faces the centre, cools by radiation thus leading to a temperature, and hence also a pressure, increase with radius. The opposite pressure and density gradients lead to Rayleigh–Taylor instabilities. This study further underlines the importance of exploring the termination phase of the CEE to the understanding of the entire CEE and its outcomes. [ABSTRACT FROM AUTHOR]

The gas-liquid equilibrium (GLE) data were determined for the mixture SO2 + N2 in the binary system of tetraethylene glycol (TeEG) + dimethyl sulfoxide (DMSO) at T = 298.15-313.15 K and p = 123.15 kPa with the SO2 partial pressures of 0.4-150 Pa. From GLE data, Henry's law constants (HLCs) were obtained. When the SO2 concentration in the gas phase was designed at ySO2 = 500 ppmv, the SO2 solubility in the binary system is located in a minimum of 9.36 mol m−3 in TeEG and a maximum of 80.34 mol m−3 in DMSO. The SO2 absorption process was reversible from the five absorption-desorption cycles, and the solvents could repeat utilisation without obvious loss of absorption capacity and the homologous SO2 desorption efficiency was nearby 98.7%. Furthermore, the spectral consequences illustrated that H-bonding was formed among TeEG, DMSO and SO2. [ABSTRACT FROM AUTHOR]

Highlights • KIC 10684673 displays variability not consistent with eclipsing binary systems. • The power spectrum reveals 10 signals with a signal-to-noise ratio of > 10. • KIC 10684673 can be modeled as a δ Scuti variable to a high level of precision. Abstract KIC 10684673 (TYC 3562-805-1) was observed by the Kepler mission, which obtained nearly 50,000 data points in the short cadence mode from May through June of 2009 for a total of about 33 days. It has been added to the Kepler Eclipsing Binary Catalog as an eclipsing binary. However it is flagged as uncertain in nature. Upon visual inspection, it is found the light curve is not consistent with features present in light curves from typical eclipsing binary systems. Instead, it shows features more consistent with pulsation. In the present study, it is shown the light curve can be satisfactorily modeled by considering the target as single, multi-modal δ Scuti pulsator. [ABSTRACT FROM AUTHOR]

NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with four components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer data set. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the Zeeman Stokes V signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding M Aa = 14.9 ± 0.5 M⊙, M Ab = 3.9 ± 0.7 M⊙, and M C = 7.8 ± 0.7 M⊙. The rotational period obtained from longitudinal magnetic field 〈 B |$z$| 〉 measurements is P rot = 1.09468(7) d, consistent with previous results. Modelling of 〈 B |$z$| 〉 indicates a surface dipole magnetic field strength of ∼8 kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric Hα emission, and we find marginal evidence of emission at the expected level (∼1 per cent of the continuum). [ABSTRACT FROM AUTHOR]

We introduce the Ophiuchus DIsc Survey Employing ALMA (ODISEA), a project aiming to study the entire population of Spitzer -selected protoplanetary discs in the Ophiuchus Molecular Cloud (∼300 objects) from both millimetre continuum and CO isotopologues data. Here we present 1.3 mm/230 GHz continuum images of 147 targets at 0.2 arcsec (28 au) resolution and a typical rms of 0.15 mJy. We detect a total of 133 discs, including the individual components of 11 binary systems and 1 triple system. 60 of these discs are spatially resolved. We find clear substructures (inner cavities, rings, gaps, and/or spiral arms) in eight of the sources and hints of such structures in another four discs. We construct the disc luminosity function for our targets and perform preliminary comparisons to other regions. A simple conversion between flux and dust mass (adopting standard assumptions) indicates that all discs detected at 1.3 mm are massive enough to form one or more rocky planets. In contrast, only ∼50 discs (∼1/3 of the sample) have enough mass in the form of dust to form the canonical 10 M⊕ core needed to trigger runaway gas accretion and the formation of gas giant planets, although the total mass of solids already incorporated into bodies larger than cm scales is mostly unconstrained. The distribution in continuum disc sizes in our sample is heavily weighted towards compact discs: most detected discs have radii < 15 au, while only 23 discs (⁠|${\sim }15{{\ \rm per\ cent}}$| of the targets) have radii > 30 au. [ABSTRACT FROM AUTHOR]

White dwarfs (WDs) are the stellar core remnants of low mass (⁠|${\lesssim }8\, {\rm M_{\odot }})$| stars. They are typically divided into three main composition groups: oxygen–neon (ONe), carbon–oxygen (CO), and helium (He) WDs. The evolution of binary systems can significantly change the evolution of the binary stellar components. In particular, striping the envelope of an evolved star can give rise to a core remnant, which can later evolve into a WD with significantly different composition. Here we focus on the formation and evolution of hybrid HeCO WDs. We follow the formation and stellar evolution of such WDs for a range of initial conditions and provide their detailed structure, mass–radius relation and luminosity–temperature evolution. We confirm that both low-mass WDs (⁠|${\lt }0.45\, {\rm M_{\odot }},$| typically thought to be He-WDs) and intermediate-mass WDs (0.45 < M WD ≤ 0.7, typically thought to be CO-WDs) could in fact be hybrid HeCO WDs, with |$5\hbox{-}25\, (75\hbox{-}95){{\ \rm per\ cent}}$| of their mass in He (CO). We use population synthesis calculations to infer the birth rate and properties of such WDs. We find that hybrid HeCO-WD comprise the majority of young (<2 Gyr) WDs in binaries, but are rarer among older WDs in binaries. The high frequency and large He content of such WDs could have an important role in WD–WD mergers, and may give rise to sub-Chandrasekhar thermonuclear supernova explosions. [ABSTRACT FROM AUTHOR]

For a sample of 38 galactic globular clusters (GCs), we confront the observed distributions of blue straggler (BS) proper motions and masses (derived from isochrone fitting) from the BS catalogue of Simunovic & Puzia with theoretical predictions for each of the two main competing BS formation mechanisms. These are mass transfer from an evolved donor on to a main-sequence (MS) star in a close binary system, and direct collisions involving MS stars during binary encounters. We use the FEWBODY code to perform simulations of single–binary and binary–binary interactions. This provides collisional velocity and mass distributions for comparison to the observed distributions. Most clusters are consistent with BSs derived from a dynamically relaxed population, supportive of the binary mass-transfer scenario. In a few clusters, including all the post-core collapse clusters in our sample, the collisional velocities provide the best fit. [ABSTRACT FROM AUTHOR]

Cosmological observations over past couple of decades favor our universe with a tiny positive cosmological constant. Presence of cosmological constant not only imposes theoretical challenges in gravitational wave physics, it has also observational relevance. Inclusion of cosmological constant in linearized theory of gravitational waves modifies the power radiated quadrupole formula. There are two types of observations which can be impacted by the modified quadrupole formula. One is the orbital decay of an inspiraling binary and other is the modification of the waveform at the detector. Modeling a compact binary system in an elliptic orbit on de Sitter background, we obtain energy and angular momentum radiation due to emission of gravitational waves. We also investigate the evolution of orbital parameters under back reaction and its impact on orbital decay rate. In the limit to circular orbit, our result matches to that obtained in [B. Bonga and J. S. Hazboun, Phys. Rev. D96 (2017) 064018, arXiv:1708.05621 ]. [ABSTRACT FROM AUTHOR]

We present an analysis of the XMM–Newton observation of the symbiotic star AG Peg, obtained after the end of its 2015 outburst. The X-ray emission of AG Peg is soft and of thermal origin. AG Peg is an X-ray source of class β of the X-ray sources among the symbiotic stars, whose X-ray spectrum is well matched by a two-temperature optically thin plasma emission (kT 1∼ 0.14 keV and kT 2∼ 0.66 keV). The X-ray emission of the class β sources is believed to originate from colliding stellar winds (CSWs) in a binary system. If we adopt the CSW picture, the theoretical CSW spectra match well the observed properties of the XMM–Newton spectra of AG Peg. However, we need a solid evidence that a massive-enough hot-star wind is present in the post-outburst state of AG Peg to proof the validity of the CSW picture for this symbiotic binary. No short-term X-ray variability is detected while the UV emission of AG Peg shows stochastic variability (flickering) on time-scales of minutes and hours. [ABSTRACT FROM AUTHOR]

We use Hubble Space Telescope multicolour photometry of the globular cluster 47 Tucanae to uncover a population of 24 objects with no previous classification that are outliers from the single-star model tracks in the colour–magnitude diagram and yet are likely cluster members. By comparing those sources with evolutionary models and X-ray source catalogues, we were able to show that the majority of those sources are likely binary systems that do not have any X-ray source detected nearby, most possibly formed by a white dwarf and a main-sequence star and a small number of possible double-degenerate systems. [ABSTRACT FROM AUTHOR]

Algol-type binary systems are the product of rapid mass transfer between the initially more massive component to its companion. It is still unknown whether the process is conservative, or whether substantial mass is lost from the system. The history of a system prior to mass exchange is imprinted in the photospheric chemical composition, in particular in the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency of mass-transfer processes in the components of a classical Algol-type system, δ Librae. The present analysis is based on new spectroscopic data (ground-based high-resolution échelle spectra) and extracted archival photometric observations (space-based measurements from the STEREO satellites). In the orbital solution, non-Keplerian effects on the radial-velocity variations were taken into account. This reduces the primary's mass by 1.1 |$\, {\rm M}_\odot$| (∼23 per cent) significantly in comparison to previous studies, and removes a long-standing discrepancy between the radius and effective temperature. A spectral disentangling technique is applied to the échelle observations and the spectra of the individual components are separated. Atmospheric and abundance analyses are performed for the mass-gaining component and we found C/N =1.55 ± 0.40 for this star. An extensive set of evolutionary models (3.5 × 106) for both components are calculated from which the best-fitting model is derived. It is found that β, the parameter that quantifies the efficiency of mass-loss from a binary system, is close to zero. This means that the mass transfer in δ Lib is mostly conservative with little mass-loss from the system. [ABSTRACT FROM AUTHOR]

A prerequisite for probing theoretical evolutionary models for high-mass stars is the determination of stellar physical properties with a high accuracy. We do this for three binary systems containing components with masses above 10 |$\, {\rm M}_\odot$|⁠ : V478 Cyg, AH Cep, and V453 Cyg. New high-resolution and high-S/N échelle spectra were secured and analysed using spectral disentangling, yielding improved orbital elements and the individual spectra for the component stars. In conjunction with a re-analysis of archival light curves, the stellar masses and radii were measured to accuracies of 1.5–2.5 per cent and 1.0–1.9 per cent, respectively. Detailed spectroscopic analysis then yielded atmospheric parameters and abundances for C, N, O, Mg, and Si. Abundances were also determined for V578 Mon. These results allowed a detailed comparison to the predictions of stellar evolutionary models. No star in our sample fits its position on the evolutionary track for its dynamical mass, leaving mass discrepancy (or alternatively overluminosity) an open problem in theoretical modelling. Moreover, the CNO abundances cluster around the initial values with mean values log (N/C) = −0.56 ± 0.06 and log (N/O) = −1.01 ± 0.06. No trend in the CNO abundances for single OB stars are found for the eight high-mass stars analysed here, as well in an extended sample including literature results. This opens an important question on the role of binarity in terms of tides on damping internal mixing in stars residing in binary systems. [ABSTRACT FROM AUTHOR]

In a series of recent papers, it has been proposed that high-field magnetic white dwarfs are the result of close binary interaction and merging. Population synthesis calculations have shown that the origin of isolated highly magnetic white dwarfs is consistent with the stellar merging hypothesis. In this picture, the observed fields are caused by an α–Ω dynamo driven by differential rotation. The strongest fields arise when the differential rotation equals the critical break up velocity and result from the merging of two stars (one of which has a degenerate core) during common envelope evolution or from the merging of two white dwarfs. We now synthesize a population of binary systems to investigate the hypothesis that the magnetic fields in the magnetic cataclysmic variables also originate during stellar interaction in the common envelope phase. Those systems that emerge from common envelope more tightly bound form the cataclysmic variables with the strongest magnetic fields. We vary the common envelope efficiency parameter and compare the results of our population syntheses with observations of magnetic cataclysmic variables. We find that common envelope interaction can explain the observed characteristics of these magnetic systems if the envelope ejection efficiency is low. [ABSTRACT FROM AUTHOR]

We investigate remnant neutron star masses (in particular, the minimum allowed mass) by performing advanced stellar evolution calculations and neutrino-radiation hydrodynamics simulations for core-collapse supernova explosions. We find that, based on standard astrophysical scenarios, low-mass carbon-oxygen cores can have sufficiently massive iron cores that eventually collapse, explode as supernovae, and give rise to remnant neutron stars that have a minimum mass of 1.17 M⊙– compatible with the lowest mass of the neutron star precisely measured in a binary system of PSR J0453+1559. [ABSTRACT FROM AUTHOR]

We analysed recent K2 data of the short-period eclipsing binary system HW Vir, which consists of a hot subdwarf-B type primary with an M-dwarf companion. We determined the mid-times of eclipses, calculated O–C diagrams, and an average shift of the secondary minimum. Our results show that the orbital period is stable within the errors over the course of the 70 days of observations. Interestingly, the offset from mid-orbital phase between the primary and the secondary eclipses is found to be 1.62 s. If the shift is explained solely by light-travel time, the mass of the sdB primary must be 0.26 M⊙, which is too low for the star to be core-helium burning. However, we argue that this result is unlikely to be correct and that a number of effects caused by the relative sizes of the stars conspire to reduce the effective light-travel time measurement. After removing the flux variation caused by the orbit, we calculated the amplitude spectrum to search for pulsations. The spectrum clearly shows periodic signal from close to the orbital frequency up to 4600 µHz, with the majority of peaks found below 2600 µHz. The amplitudes are below 0.1 part-per-thousand, too low to be detected with ground-based photometry. Thus, the high-precision data from the Kepler spacecraft has revealed that the primary of the HW Vir system is a pulsating sdBV star. We argue that the pulsation spectrum of the primary in HW Vir differs from that in other sdB stars due to its relatively fast rotation that is (nearly) phase-locked with the orbit. [ABSTRACT FROM AUTHOR]

The first gravitational wave detections of mergers between black holes and neutron stars represent a remarkable new regime of high-energy transient astrophysics. The signals observed with LIGO-Virgo detectors come from mergers of extreme physical objects which are the end products of stellar evolution in close binary systems. To better understand their origin and merger rates, we have performed binary population syntheses at different metallicities using the new grid-based binary population synthesis code ComBinE. Starting from newborn pairs of stars, we follow their evolution including mass-loss, mass transfer and accretion, common envelopes, and supernova explosions. We apply the binding energies of common envelopes based on dense grids of detailed stellar structure models, make use of improved investigations of the subsequent Case BB Roche lobe overflow and scale supernova kicks according to the stripping of the exploding stars. We demonstrate that all the double black hole mergers, GW150914, LVT151012, GW151226, GW170104, GW170608, and GW170814, as well as the double neutron star merger GW170817, are accounted for in our models in the appropriate metallicity regime. Our binary interaction parameters are calibrated to match the accurately determined properties of Galactic double neutron star systems, and we discuss their masses and types of supernova origin. Using our default values for the input physics parameters, we find a double neutron star merger rate of |${3.0}\, \mathrm{Myr}^{-1}$| for Milky-Way equivalent galaxies. Our upper limit to the merger-rate density of double neutron stars is |$R\simeq {400} \, \mathrm{yr}^{-1}\, {\rm Gpc}^{-3}$| in the local Universe (⁠|$z$| = 0). [ABSTRACT FROM AUTHOR]

The gamma-ray emission detected from several microquasars can be produced by relativistic electrons emitting through inverse Compton scattering. In particular, the GeV emission detected from Cygnus X-3, and its orbital phase dependence, strongly suggests that the emitting electrons are accelerated in a relativistic jet, and that the optical companion provides the dominant target. Here, we study the effects related to particle transport in the framework of the relativistic jet scenario. We find that even in the most compact binary systems, with parameters similar to Cygnus X-3, particle transport can have a substantial influence on the GeV light curve unless the jet is slow, β < 0.7. In more extended binary systems, strong impact of particle transport is nearly unavoidable. Thus, even for a very compact system such as Cygnus X-3, particle transport significantly affects the ability of one-zone models to infer the properties of the gamma-ray production site based on the shape of the GeV lightcurve. We conclude that a detailed study of the gamma-ray spectrum can further constrain the structure and other properties of the gamma-ray emitter in Cygnus X-3, although such a study should account for gamma–gamma attenuation, since it may strongly affect the spectrum above |$5\rm \, GeV$|⁠. [ABSTRACT FROM AUTHOR]

Graphical abstract A novel bifunctional nanocomposites of LDHs@PAB exhibited effective and simultaneous removal for Cr(VI) and MO. Highlights • Acicular nanoflakes of Ni/Al LDH successfully decorated biomass-based porous carbons. • Ni/Al@PAB can simultaneously remove Cr(VI) and MO from the binary system. • The synergistic effect of PAB and Ni/Al LDH endows simultaneous and efficient removal. Abstract Layered double hydroxides (LDHs) are currently attracting intense research interests as pollutant adsorbent due to its low cost, non-toxicity, structure amenability and anion exchange capability. Herein, 3-dimensional (3D) flower-like Ni/Al LDH were prepared to decorate H 3 PO 4 activated biomass-derived porous carbons (PAB) via a facile and green hydrothermal method. The as-synthesized nanocomposites (Ni/Al@PAB) displayed favorable removal performance towards both Cr(VI) and methyl orange (MO) from aqueous solution due to the inherited excellent Cr(VI) removal ability from PAB and MO removal ability from Ni/Al LDH. In single-component removal system, the maximum adsorption capacity of 271.5 and 412.8 mg/g for Cr(VI) and MO were achieved on Ni/Al@PAB, respectively. Remarkably, the removal capacity of Cr(VI) and MO both increased in the Cr(VI) MO binary system due to the synergistic effect including, (i) additional adsorption sites of N-containing groups from MO, (ii) electrostatic interactions by the reduced Cr(III), and (iii) mutual thermal compensation in the binary system. This work paved the way for designing novel LDHs-decorated porous carbon adsorbents and revealed that the acicular Ni/Al LDH decorated PAB could be applied as efficient and simultaneous adsorbent for coexisting toxic pollutants situations. [ABSTRACT FROM AUTHOR]

We evolve stellar models to study the common envelope (CE) interaction of an early asymptotic giant branch star of initial mass |$5\, \rm M_{\odot }$| with a companion star of mass ranging from 0.1 to |$2\, \rm M_{\odot }$|⁠. We model the CE as a fast stripping phase in which the primary experiences rapid mass loss and loses about 80 per cent of its mass. The post-CE remnant is then allowed to thermally readjust during a Roche lobe overflow (RLOF) phase and the final binary system and its orbital period are investigated. We find that the post-CE RLOF phase is long enough to allow nuclear burning to proceed in the helium shell. By the end of this phase, the donor is stripped of both its hydrogen and helium and ends up as carbon–oxygen white dwarf of mass about |$0.8\, \rm M_{\odot }$|⁠. We study the sensitivity of our results to initial conditions of different companion masses and orbital separations at which the stripping phase begins. We find that the companion mass affects the final binary separation and that helium-shell burning causes the star to refill its Roche lobe leading to post-CE RLOF. Our results show that double mass transfer in such a binary interaction is able to strip the helium and hydrogen layers from the donor star without the need for any special conditions or fine tuning of the binary parameters. [ABSTRACT FROM AUTHOR]