Binary Axis Research Articles

Studying geometry of the ultraluminous X-ray pulsar Swift J0243.6+6124 using X-ray and optical polarimetry

Discovery of pulsations from a number of ultra-luminous X-ray (ULX) sources proved that accretion onto neutron stars can produce luminosities exceeding the Eddington limit by several orders of magnitude. The conditions necessary to achieve such high luminosities as well as the exact geometry of the accretion flow in the neutron star vicinity are, however, a matter of debate. The pulse phase-resolved polarization measurements that became possible with the launch of the Imaging X-ray Polarimetry Explorer (IXPE) can be used to determine the pulsar geometry and its orientation relative to the orbital plane. They provide an avenue to test different theoretical models of ULX pulsars. In this paper we present the results of three IXPE observations of the first Galactic ULX pulsar Swift J0243.6+6124 during its 2023 outburst. We find strong variations in the polarization characteristics with the pulsar phase. The average polarization degree increases from about 5<!PCT!> to 15<!PCT!> as the flux dropped by a factor of three in the course of the outburst. The polarization angle (PA) as a function of the pulsar phase shows two peaks in the first two observations, but changes to a characteristic sawtooth pattern in the remaining data set. This is not consistent with a simple rotating vector model. Assuming the existence of an additional constant polarized component, we were able to fit the three observations with a common rotating vector model and obtain constraints on the pulsar geometry. In particular, we find the pulsar angular momentum inclination with respect to the line of sight of $i_ p the magnetic obliquity of $ p and the pulsar spin position angle of $ p which significantly differs from the constant component PA of about 10 Combining these X-ray measurements with the optical PA, we find evidence for at least a 30 misalignment between the pulsar angular momentum and the binary orbital axis.

Hidden Companions to Intermediate-mass Stars. XXI. Discovery of a 0.5 M ⊙, 1.5 au Companion to Sadachbia = Gamma Aquarii* *Based on observations collected at the European Southern Observatory, Chile, Program ID 113.26GM.001.

Sadachbia = Gamma Aquarii is a nearby A0V star that was suspected to be a spectroscopic binary. Here we report on the direct detection of a companion with a K band flux ratio of 1.2% at a projected separation of 38.2 mas based on a VLTI/GRAVITY near-infrared interferometric observation. The implied mass and separation of the companion are 0.46 M ⊙ and 1.5 au based on the Gaia DR3 distance (or 0.55 M ⊙ and 1.9 au if the discrepant Hipparcos distance is used instead). The companion explains the X-ray emission of γ Aqr and the orbital motion with a period of about one year likely explains the discrepant Gaia and Hipparcos parallaxes. Further observations are necessary to measure the binary semimajor axis but it is likely that the system will undergo common envelope evolution. The primary is partially resolved with an angular diameter of 0.52 mas.

Disk-induced Binary Precession: Implications for Dynamics and Multimessenger Observations of Black Hole Binaries

Many studies have recently documented the orbital response of eccentric binaries accreting from thin circumbinary disks, characterizing the change in the binary semimajor axis and eccentricity. We extend these calculations to include the precession of the binary’s longitude of periapse induced by the circumbinary disk, and we characterize this precession continuously with binary eccentricity e b for equal mass components. This disk-induced apsidal precession is prograde with a weak dependence on the binary eccentricity when e b ≲ 0.4 and decreases approximately linearly for e b ≳ 0.4; yet at all e b binary precession is faster than the rates of change to the semimajor axis and eccentricity by an order of magnitude. We estimate that such precession effects are likely most important for subparsec separated binaries with masses ≲107 M ⊙, like LISA precursors. We find that accreting, equal-mass LISA binaries with M < 106 M ⊙ (and the most massive M ∼ 107 M ⊙ binaries out to z ∼ 3) may acquire a detectable phase offset due to the disk-induced precession. Moreover, disk-induced precession can compete with general relativistic precession in a vacuum, making it important for observer-dependent electromagnetic searches for accreting massive binaries—like Doppler boost and binary self-lensing models—after potentially only a few orbital periods.

Eccentric Minidisks in Accreting Binaries

We show that gas disks around the components of an orbiting binary system (so-called minidisks) may be susceptible to a resonant instability that causes the minidisks to become significantly eccentric. Eccentricity is injected by, and also induces, regular impacts between the minidisks at roughly the orbital period of the binary. Such eccentric minidisks are seen in vertically integrated, two-dimensional simulations of a circular, equal-mass binary accreting from a circumbinary gas disk with a Γ-law equation of state. Minidisk eccentricity is suppressed by the use of an isothermal equation of state. However, the instability still operates and can be revealed in a minimal disk-binary simulation by removing the circumbinary disk and feeding the minidisks from the component positions. Minidisk eccentricity is also suppressed when the gravitational softening length is large (≳4% of the binary semimajor axis), suggesting that its absence could be an artifact of widely adopted numerical approximations; a follow-up study in three dimensions with well-resolved, geometrically thin minidisks (aspect ratios ≲0.02) may be needed to assess whether eccentric minidisks can occur in real astrophysical environments. If they can, the electromagnetic signature may be important for discriminating between binary and single black hole scenarios for quasiperiodic oscillations in active galactic nuclei; in turn, this might aid in targeted searches with pulsar timing arrays for individual supermassive black hole binary sources of low-frequency gravitational waves.

The chaotic four-body problem in Newtonian gravity – II. An ansatz-based approach to analytical solutions

ABSTRACT In this paper, we continue our analysis of the chaotic four-body problem and our study of binary–binary interactions in star clusters. We present a general ansatz-based analytical treatment using statistical mechanics, where each outcome of the four-body problem is regarded as some variation of the three-body problem. For example, when two single stars are produced (the 2 + 1 + 1 outcome), each ejection event is modelled as its own three-body interaction by assuming that the ejections are well separated in time. This is a generalization of the approach adopted in Paper I, based on the density-of-states formalism. There are three possible outcomes for the four-body problem with negative total energies: 2 + 2, 2 + 1 + 1, and 3 + 1. For each outcome, we apply an ansatz-based approach to deriving analytical distribution functions that describe the properties of the products of chaotic four-body interactions involving point particles. To test our theoretical distributions, we perform a set of scattering simulations in the equal-mass point-particle limit using FEWBODY, where we vary the initial ratio of binary semimajor axes. We compare our final theoretical distributions to the simulations for each particular scenario, finding consistently good agreement between the two. The highlights of our results include that binary–binary scatterings act to systematically destroy binaries producing instead a binary and two ejected stars (when the initial binary semimajor axes are similar) or a stable triple (when the initial semimajor axes are very different). The 2 + 2 outcome produces the widest binaries, and the 2 + 1 + 1 outcome produces the most compact binaries.

Powerful in pearls and Willie Brown’s mistress: a computational analysis of gendered news coverage of Kamala Harris on the partisan extremes

ABSTRACT This study uses a mix of traditional and computational content analysis to track digital news coverage of U.S. Vice President Kamala Harris during and immediately after the 2020 general elections. It’s well documented that female politicians, especially women of color, face biased coverage in the political press. In this paper, we explore how these dynamics play out in the modern hyper-polarized digital media landscape. Our corpus includes roughly 17,000 stories published online between August 2020 and April 2021 by news organizations we categorized along a binary axis of partisanship between Republican and Democrat. Our findings show that sexist, racialized coverage of Harris is most prevalent in news sources shared by mostly Republican voters. Coverage in news sources shared by registered Democratic voters, meanwhile, tended to treat Harris as a celebrity, often fixating on her wardrobe and personal life. We ponder implications for both gender equity in civic life and future feminist media scholarship.

Eccentric binaries in retrograde discs

ABSTRACT Modern numerical hydrodynamics tools have recently enabled detailed examinations of binaries accreting from prograde circumbinary discs. These have reframed the current understanding of binary-disc interactions and disc driven orbital evolution. We present the first full-domain grid-based hydrodynamics simulations of equal-mass, eccentric binaries accreting from retrograde circumbinary discs. We study binary eccentricities that span e = 0.0 to e = 0.8 continuously, and explore the influence of retrograde accretion on the binary orbital response, disc morphology, and observational properties. We find that, at all eccentricities, retrograde accretion shrinks the binary semimajor axis and pumps its eccentricity leading to the previously identified possibility of highly eccentric mergers. Contrary to past studies and models, we observe gravitational forces to dominate the binary’s orbital evolution as opposed to the physical accretion of mass and momentum. Retrograde accretion variability also differs strongly from prograde solutions. Preeminently, binaries with e &amp;gt; 0.55 reveal a unique two-period, double-peaked accretion signature that has not previously been identified. We additionally find evidence for the emergence of retrograde Lindblad resonances at large eccentricities in accordance with predictions from linear theory. Our results suggest that some astrophysical binaries for which retrograde accretion is possible will experience factors-of-a-few times faster orbital decay than in prograde discs and will have their eccentricities pumped beyond the limits found from prograde solutions. Such effects could lead to rapid inward migration for some young stellar binaries, the detection of highly eccentric LISA mergers, and the tentatively observed turnover at the low-frequency end of the gravitational wave background.

A dependence of binary and planetary system destruction on subtle variations in the substructure in young star-forming regions

ABSTRACT Simulations of the effects of stellar fly-bys on planetary systems in star-forming regions show a strong dependence on subtle variations in the initial spatial and kinematic substructure of the regions. For similar stellar densities, the more substructured star-forming regions disrupt up to a factor of 2 more planetary systems. We extend this work to look at the effects of substructure on stellar binary populations. We present N-body simulations of substructured, and non-substructured (smooth) star-forming regions in which we place different populations of stellar binaries. We find that for binary populations that are dominated by close (&amp;lt;100 au) systems, a higher proportion are destroyed in substructured regions. However, for wider systems (&amp;gt;100 au), a higher proportion are destroyed in smooth regions. The difference is likely due to the hard–soft or fast–slow boundary for binary destruction. Hard (fast/close) binaries are more likely to be destroyed in environments with a small velocity dispersion (kinematically substructured regions), whereas soft (slow/wide) binaries are more likely to be destroyed in environments with higher velocity dispersions (non-kinematically substructured regions). Due to the vast range of stellar binary semimajor axes in star-forming regions (10−2 to 104 au), these differences are small and hence unlikely to be observable. However, planetary systems have a much smaller initial semimajor axis range (likely ∼1–100 au for gas giants) and here the difference in the fraction of companions due to substructure could be observed if the star-forming regions that disrupt planetary systems formed with similar stellar densities.

Evidence for a Black Hole Spin–Orbit Misalignment in the X-Ray Binary Cyg X-1

Recently, the accretion geometry of the black hole X-ray binary Cyg X-1 was probed with the X-ray polarization. The position angle of the X-ray-emitting flow was found to be aligned with the position angle of the radio jet in the plane of the sky. At the same time, the observed high polarization degree could be obtained only for a high inclination of the X-ray-emitting flow, indicating a misalignment between the binary axis and the black hole spin. The jet, in turn, is believed to be directed by the spin axis; hence, a similar misalignment is expected between the jet and binary axes. We test this hypothesis using very long (up to about 26 yr) multiband radio observations. We find a misalignment of 20°–30°. However, contrary to the earlier expectations, the jet and binary viewing angles are found to be similar, while the misalignment is seen between the position angles of the jet and the binary axis on the plane of the sky. Furthermore, the presence of the misalignment calls into question our understanding of the evolution of this binary system.

The Emergence of a Neutral Wind Region in the Orbital Plane of Symbiotic Binaries during Their Outbursts

Accretion of mass onto a white dwarf (WD) in a binary system can lead to stellar explosions. If a WD accretes from stellar wind of a distant evolved giant in a symbiotic binary, it can undergo occasional outbursts in which it brightens by several magnitudes, produces a low- and high-velocity mass outflow, and, in some cases, ejects bipolar jets. In this paper, we complement the current picture of these outbursts by the transient emergence of a neutral region in the orbital plane of symbiotic binaries consisting of wind from the giant. We prove its presence by determining H0 column densities (N H) in the direction of the WD and at any orbital phase of the binary by modeling the continuum depression around the Lyα line caused by Rayleigh scattering on atomic hydrogen for all suitable objects, i.e., eclipsing symbiotic binaries, for which a well-defined ultraviolet spectrum from an outburst is available. The N H values follow a common course along the orbit with a minimum and maximum of a few times 1022 and 1024 cm−2 around the superior and inferior conjunction of the giant, respectively. Its asymmetry implies an asymmetric density distribution of the wind from the giant in the orbital plane with respect to the binary axis. The neutral wind is observable in the orbital plane owing to the formation of a dense disk-like structure around the WD during outbursts, which blocks ionizing radiation from the central burning WD in the orbital plane.

Grid-based simulations of polar circumbinary discs: polar alignment and vortex formation

ABSTRACT We describe the first grid-based simulations of the polar alignment of a circumbinary disc. We simulate the evolution of an inclined disc around an eccentric binary using the grid-based code athena++ . The use of a grid-based numerical code allows us to explore lower disc viscosities than have been examined in previous studies. We find that the disc aligns to a polar orientation when the α viscosity is high, while discs with lower viscosity nodally precess with little alignment over 1000 binary orbital periods. The time-scales for polar alignment and disc precession are compared as a function of disc viscosity, and are found to be in agreement with previous studies. At very low disc viscosities (e.g. α = 10−5), anticyclonic vortices are observed along the inner edge of the disc. These vortices can persist for thousands of binary orbits, creating azimuthally localized overdensities and multiple pairs of spiral arms. The vortex is formed at ∼3–4 times the binary semimajor axis, close to the inner edge of the disc, and orbits at roughly the local Keplerian speed. The presence of a vortex in the disc may play an important role in the evolution of circumbinary systems, such as driving episodic accretion and accelerating the formation of polar circumbinary planets.

Pyrite contact twins.

Two examples of contact twins in pyrite from Peru are described. The first one, from Pasto Bueno ore deposit, shows the pyritohedron {120} as principal form, accompanied by the {111} octahedron and {100} cube as secondary forms, giving a lenticular aspect. (111) is the composition plane, and the twin operation is any one of the three binary axes ⟨110⟩ within this plane. The second one (unknown ore deposit) presents two forms, the octahedron {111} and the pyritohedron {120}; the two crystals in the twin are elongated along [101] and [011], respectively, producing a V profile. It is a reflection twin where the twin plane (110) coincides with the composition plane. These twins are by merohedry. Another contact twin is known in the literature, reported by Gaubert [Bull. Soc. Fr. Minéral. Cristallogr. (1928), 51, 211-212] who described it as a spinel twin, i.e. a reflection twin with twin and composition plane (111); here it is shown that it is actually a rotation twin in which the twin operation is a 180° rotation about any of the three equivalent directions ⟨211⟩, contained in the (111) composition plane. The occurrence of these twins as well as the doubtfulness of the spinel twin in pyrite shows a direct relationship with the structural interpretation based on the pseudo-symmetry of the crystallographic orbits.

Experimental outdoor performance assessment and energy efficiency of 11.28 kWp grid tied PV systems with sun tracker installed in saharan climate: A case study in Ghardaia, Algeria

In recent years, the demand for grid tied solar photovoltaic systems has been rising fleetly, due to the low cost of solar panels, storage systems, and inverter equipment. The expertise of the grid related photovoltaic solar system attached sun trackers doesn't depend on the following factors, the amount of sunshine, angular travel, positioning frequency, and the region where they are installed. To comprehend how they perform in the whole world, we require assessing and comparing their performance in several parts of the country. This work details the experimental PV system setup and the analytics based on the measurements from the system in Algeria (Ghardaia City).This work exhibits detailed simulation data based on PVSYST software and compared with experimental results of an 11.28 kWp grid-connected solar system with sun tracking systems, after one year of operation at Applied Research Unit of Renewable Energy (URAER) in southern Algeria. The PV system consists of three identical 3.76 kWp solar trackers systems with the same module and inverter. This study also investigates during the real outdoor PV system operation, the yearly, monthly, and daily PV array and inverter behavior based on the performance metrics indicators, meteorological data (temperature and solar irradiation), DC and AC energy produced reference yield (YF), array yield (YA), final yield (YF), PV array and system efficiency, performance ratio (PR), PV array and system losses, and capacity factor (CF) of the whole solar photovoltaic system with sun tracker and likewise the three sub-PV systems with sun tracker following to the IEC 61,724 guidance. The electricity produced for the grid was also verified using the sunny portal application. The outcomes indicate that the binary-axis solar tracker shows a preferable performance, which collects about 20.89% further energy compared to that of the steady axis, and the one-axis tracker generates about 12.91% more energy compared to the fixed PV tracker. The energy generated (EDC) over the monitored period (2021) was 6917.50 kWh, 7810.58 kWh, and 8362.68 kWh for the steady PV system, one axis PV system, and twin axis tracking PV system, respectively. The yearly energy fed into the conventional network (EAC) over the period is 7537.4 kWh, 9962.1 kWh, and 10273.5 kWh for the stationary PV system, one axis PV system, and binary axis tracking PV system, respectively. The amount of CO2 emissions avoided over the monitored period (2021) is 4.84 tons, 5.46 tons, and 5.85 tons for the stationary PV system, one axis PV system, and twin axis tracking PV system, respectively, which can significantly contribute to cleaning the environment from pollution. The analysis shows PV module and overall system efficiency varies from (10.66%/10.26%), 10.77%/10.35%, and 10.79%/10.36% noted in July to (12.18%/11.74%, 12.34%/11.9%, and 12.41%/11.95%) noted in January for twin axis solar trackers PV systems, one axis solar trackers PV systems, and PV fixed PV systems, respectively. The analysis shows that the performance ratio (PR) varies from (72.3%, 72.4% and 71.8%) in July to (83.6%, 83.2% and 82.1%) in January and the annual average value reaches (77.95%, 77.80%, and 76.95%) for twin axis solar trackers PV systems, one axis solar trackers PV systems, and PV fixed PV systems, respectively. These performance indicators have the practical value of guiding and providing good feedback for engineers, system designers, contractors, and investors to boost the growing applications of grid-tied PV systems with a sun tracker in the same or similar location and climate conditions (Sahara environment).

Magneto-Seebeck effect in bismuth

Thermoelectricity was discovered almost two centuries ago in bismuth. The large and negative Seebeck coefficient of this semimetal remains almost flat between 300 K and 100 K. This striking feature can be understood by considering the ratio of electron and hole mobilities and the evolution of their equal densities with temperature. The large and anisotropic magneto-Seebeck effect in bismuth, on the other hand, has not been understood up to the present day. Here, we report on a systematic study of the thermopower of bismuth from room temperature down to 20 K upon application of a magnetic field of 13.8 T in the binary-bisectrix plane. The amplitude of the Seebeck coefficient depends on the orientation of the magnetic field and the anisotropy changes sign with decreasing temperature. The magneto-Seebeck effect becomes non-monotonic at low temperatures. When the magnetic field is oriented along the binary axis, the Seebeck coefficient is not the same for positive and negative fields. This so-called Umkehr effect arises because the high symmetry axes of the Fermi surface ellipsoids are neither parallel to each other nor to the high symmetry axes of the lattice. The complex evolution of thermopower can be accounted for in a large part of the ($T,B,\Theta$)-space by a model based on semiclassical transport theory and incorporating Landau quantization. The employed energy dependence of the scattering time is compatible with electron-acoustic phonon scattering. We find that the transverse Nernst response plays an important role in setting the amplitude of the longitudinal magneto-Seebeck effect. Furthermore, Landau quantization significantly affects thermoelectricity up to temperatures as high as 120 K.

Evolution of a primordial binary black hole due to interaction with cold dark matter and the formation rate of gravitational wave events

In this Paper we consider a problem of formation and evolution of orbital parameters of a binary primordial black hole (PBH) due to gravitational interaction with clustering cold dark matter (CDM). Mass and initial separation have values, which are appropriate for the problem of explanation of the LIGO/Virgo events by coalescing binary PBHs. We consider both radiation dominated and CDM dominated stages of the evolution using numerical and semi-analytical means. We show that at the end time of our numerical simulations binary's semimajor axis decreases by approximately one hundred times, while its angular momentum decreases by ten times, in comparison to the standard values, which do not take into account effects associated with CDM clustering. We check that our conclusions are hardly affected by numerical artefacts. We estimate the merger rate of binary PBHs due to emission of gravitational wave at the present time both in the standard case when the effects associated with clustering are neglected and in the case when they are taken into account and show, that these effects could increase the merger rate at least by $6-8$ times in comparison to the standard estimate. This, in turn, means, that a mass fraction of PBHs, $f$, should be smaller than it was assumed before.

KNN FOR CLASSIFICATION OF FRUIT TYPES BASED ON FRUIT FEATURES

Research related to the recognition of fruit types has been done previously. Research related to the recognition of many types of fruit applies computer vision and artificial intelligence. The purpose of this research is to apply artificial intelligence science with the KNN method to identify the type of fruit. The KNN method has a good performance in previous studies. We tried to use KNN by determining the most optimal K value. There are five types of fruit images used in this study, namely Apples, Grapes, Oranges, Mangoes, and Strawberries. The fruit image is extracted with colour, texture, and shape features with a total of 15 features, namely the average value of R, the average value of G, the average value of B, the value of skewness R, the value of skewness G, the value of skewness B, the value of grayscale entropy. , grayscale contrast value, grayscale energy value, grayscale correlation value, grayscale homogeneity value, binary area value, binary circumference value, binary major axis value, and binary minor axis value. The dataset used in this study was taken from Kaggle, with a dataset of 2750 images, each type of fruit contained 550 images, 2500 training images were used and 250 images were used for testing. The experimental results show that the KNN method with K=1 has the highest accuracy, which is 99.6%. The KNN method can be used optimally in classifying fruit types based on colour, texture, and shape features.

A survey of disc thickness and viscosity in circumbinary accretion: Binary evolution, variability, and disc morphology

ABSTRACTMuch of the parameter space relevant to the evolution of astrophysical circumbinary accretion discs remains unexplored. We have carried out a suite of circumbinary disc simulations surveying both disc thickness and kinematic viscosity, using both constant-ν and constant-α prescriptions. We focus primarily on disc aspect ratios between 0.1 and 0.033, and on viscosities between ν = 0.0005 and ν = 0.008 (in units of binary semimajor axis and orbital frequency), and specialize to circular equal-mass binaries. Both factors strongly influence the evolution of the binary semimajor axis: at ν = 0.0005, inspirals occur at aspect ratios ≲ 0.059, while at ν = 0.004 inspirals occur only at aspect ratios ≲ 0.04. Inspirals occur largely because of the increasingly strong negative torque on the binary by streams of material which lag the binary, with negligible contributions from resonant torques excited in the circumbinary disc. We find that reductions in accretion rate occur when simulations are initialized too far from the eventual quasi-steady state driven by interaction with the binary, rather than being intrinsically linked to the disc aspect ratio. We find not only that the cavity size increases as viscosity is decreased, but that thinner circumbinary discs become more eccentric. Our results suggest that supermassive black hole binaries should be driven, more rapidly than previous estimates, from ∼parsec separations to distances where gravitational waves drive their inspiral, potentially reducing the number of binaries observable by pulsar timing arrays.

Resolving Massive Black Hole Binary Evolution via Adaptive Particle Splitting

Abstract The study of the interaction of a massive black hole binary with its gaseous environment is crucial in order to be able to predict merger rates and possible electromagnetic counterparts of gravitational-wave signals. The evolution of the binary semimajor axis resulting from this interaction has been recently debated, and a clear consensus is still missing because of several numerical limitations, i.e., fixed orbit binaries or lack of resolution inside the cavity carved by the binary in its circumbinary disk. Using on-the-fly particle splitting in the 3D meshless code gizmo, we achieve hyper-Lagrangian resolution, which allows us to properly resolve the dynamics inside the cavity—in particular, for the first time, the disks that form around the two components of a live binary surrounded by a locally isothermal gaseous circumbinary disk. We show that the binary orbit decays with time for very cold and very warm disks and that the result of the interaction in the intermediate regime is strongly influenced by the disk viscosity, as this essentially regulates the fraction of mass contained in the disks around the binary components, as well as the fraction that is accreted by the binary. We find the balance between these two quantities to determine whether the binary semimajor axis decreases with time.

Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo

Intermediate-mass black holes (IMBHs) span the approximate mass range 100−105 M⊙, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150 M⊙ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200 M⊙ and effective aligned spin 0.8 at 0.056 Gpc−3 yr−1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc−3 yr−1.

Planet–planet scattering in presence of a companion star

ABSTRACT Planet–planet (P–P) scattering is a leading dynamical mechanism invoked to explain the present orbital distribution of exoplanets. Many stars belong to binary systems; therefore, it is important to understand how this mechanism works in the presence of a companion star. We focus on systems of three planets orbiting the primary star and estimate the time-scale for instability, finding that it scales with the Keplerian period for systems that have the same ratio between inner planet and binary semimajor axes. An empirical formula is also derived from simulations to estimate how the binary eccentricity affects the extent of the stability region. The presence of the secondary star affects the P–P scattering outcomes, causing a broadening of the final distribution in semimajor axis of the inner planet as some of the orbital energy of the planets is absorbed by the companion star. Repeated approaches to the secondary star also cause a significant reduction in the frequency of surviving two-planet systems in particular for larger values of the inner planet semimajor axis. The formation of Kozai states with the companion star increases the number of planets that may be tidally circularized. To predict the possible final distribution of planets in binaries, we have performed a large number of simulations where the initial semimajor axis of the inner planets is chosen randomly. For small values of the binary semimajor axis, the higher frequency of collision alters the final planet orbital distributions that, however, beyond 50 au appear to be scalable to wider binary separations.