Object Mergers Research Articles

Euclid: The rb−M* relation as a function of redshift

Core ellipticals, which are massive early-type galaxies with almost constant inner surface brightness profiles, are the result of dry mergers. During these events, a binary black hole (BBH) is formed, destroying the original cuspy central regions of the merging objects and scattering stars that are not on tangential orbits. The size of the emerging core correlates with the mass of the finally merged black hole (BH). Therefore, the determination of the size of the core of massive early-type galaxies provides key insights not only into the mass of the black hole, but also into the origin and evolution of these objects. In this work, we report the first Euclid-based dynamical mass determination of a supermassive black hole (SMBH). To this end, we study the center of NGC 1272, the second most luminous elliptical galaxy in the Perseus cluster, combining the Euclid Visible Camera (VIS) photometry coming from the Early Release Observations (EROs) of the Perseus cluster with the Visible Integral-field Replicable Unit Spectrograph (VIRUS) spectroscopic observations at the Hobby-Eberly Telescope (HET). The core of NGC 1272 is detected on the Euclid VIS image. Its size is 1.​​″29 ± 0.​​″07 or 0.45 kpc, which was determined by fitting PSF-convolved core-Sérsic and Nuker-law functions. We deproject the surface brightness profile of the galaxy, finding that the galaxy is axisymmetric and nearly spherical. The two-dimensional stellar kinematics of the galaxy is measured from the VIRUS spectra by deriving optimally regularized non-parametric line-of-sight velocity distributions. Dynamical models of the galaxy are constructed using our axisymmetric and triaxial Schwarzschild codes. We measure a BH mass of (5 ± 3)×109 M⊙, which is in line with the expectation from the MBH − rb correlation, but is eight times larger than predicted by the MBH − σ correlation (at 1.8σ significance). The core size, rather than the velocity dispersion, allows one to select galaxies harboring the most massive BHs. The spatial resolution, wide area coverage, and depth of the Euclid (Wide and Deep) surveys allow us to find cores of passive galaxies that are larger than 2 kpc at a redshift of up to 1.

Searching for triple systems unbound by supernovae

ABSTRACT A large fraction of massive stars are found in higher order systems where the presence of a tertiary may significantly modify the system’s evolution. In particular, it can lead to increased numbers of compact object binaries and accelerate their mergers with important implications for gravitational wave observations. Using Gaia, we constrain the number of Galactic supernovae that produce unbound triples. We do this by searching 8 supernova remnants for stars with consistent Gaia parallaxes and paths intersecting near the centre of the supernova remnant at a time consistent with the age of the remnant. We find no candidates for unbound triple systems. Combined with prior work, less than 11.4 per cent of supernovae leave behind unbound triples at a 90 per cent confidence limit. The absence of such systems limits their role in the evolution of massive stars and the formation of merging compact objects.

Constraining the overcontact phase in massive binary evolution. III. Period stability of known B+B and O+B overcontact systems

Binary systems play a crucial role in massive star evolution. Systems composed of B-type and O-type stars are of particular interest due to their potential to lead to very energetic phenomena or the merging of exotic compact objects. We aim to determine the orbital period variations of a sample of B+B and O+B massive overcontact binaries, with the primary objectives of characterizing the evolutionary timescales of these systems and addressing the existing discrepancy between observational data and theoretical predictions derived from population synthesis models. We used Period04 to analyze archival photometric data going back a century for a sample of seven binary systems to measure their orbital periods. We then determine the period variations using a linear fit. We find that the period variation timescales of five truly overcontact binary systems align with the nuclear timescale, in agreement with previous findings for more massive overcontact binaries. Additionally, we noticed a clear distinction between the five systems that had been unambiguously classified as overcontact systems and both SV Cen and VFTS 066, which seem to be evolving on thermal timescales and might be misclassified as overcontact systems. In the case of the five overcontact binaries, our results indicate a noticeable mismatch between the observational data and the theoretical predictions derived from population synthesis models. Furthermore, our results suggest that additional physical mechanisms must be investigated to compare the observed variations more thoroughly with theoretical predictions.

The X-ray binaries in M83: Will any of them form gravitational wave sources for LIGO-VIRGO-KAGRA?

There are 214 X-ray point sources (LX > 1035 erg s−1) identified as X-ray binaries (XRBs) in the nearby spiral galaxy M83. Since XRBs are powered by accretion onto a neutron star (NS) or a black hole (BH) from a companion or donor star, these systems are promising progenitors of merging double compact objects (DCOs): BH-BH, BH-NS, or NS-NS systems. The connection (i.e., XRBs evolving into DCOs) may provide some hints to the as-yet-unanswered question: what is the origin of the LIGO, Virgo, and KAGRA mergers? Available observations do not allow us to determine what the final fate of the XRBs observed in M83 will be. However, we can use an evolutionary model of isolated binaries to reproduce the population of XRBs in M83 by matching model XRB numbers, types, and luminosities to observations. Knowing the detailed properties of M83 model XRBs (donor and accretor masses, and their evolutionary ages and orbits), we follow their evolution to the deaths of donor stars to check whether any merging DCOs are formed. Although all merging DCOs in our isolated binary evolution model go through the XRB phase (defined as reaching X-ray luminosity from RLOF or wind accretion onto NSs or BHs above 1035 erg s−1), only very few XRBs evolve to form merging (in Hubble time) DCOs. For M83, with its solar-like metallicity stars and continuous star formation, we find that only ∼1 − 2% of model XRBs evolve into merging DCOs depending on the adopted evolutionary physics. This is caused by (i) the merger of the donor star with a compact object during the common envelope phase, (ii) a binary disruption at the supernova explosion of a donor star, (iii) the formation of a DCO on a wide orbit (merger time longer than Hubble time).

Forming merging double compact objects with stable mass transfer

Context. Merging double compact objects (COs) are one of the possible endpoints of the evolution of stellar binary systems. As they represent the inferred sources of every detected gravitational wave (GW) signal, modeling their progenitors is of paramount importance both to gain a better understanding of gravitational physics and to constrain stellar evolution theory. Aims. Stable mass transfer (MT) between a donor star and a black hole (BH) is one of the proposed tightening mechanisms to form binary BHs that merge within the lifetime of the universe. We aim to assess the potential of stable non-conservative MT to produce different pairings of compact objects including BHs, neutron stars (NSs) and white dwarfs (WDs). Methods. We investigated the conditions (orbital periods and mass ratios) required for MT between a star and a CO to be stable and to lead to binary COs that merge within a Hubble time. We use published results on the response of the stellar radii to rapid mass loss, covering different evolutionary stages and masses. Coupled with analytical models of orbital evolution, we determined the boundary for unstable MT as well as the post-interaction properties of binaries undergoing stable MT. In addition, we investigated the impact of the angular momentum loss prescription in the resulting hardening by accounting for both the isotropic re-emission from the accretor’s vicinity and mass outflow from the second Lagrangian point. Results. Stable MT in systems with a CO + Roche lobe-filling star, in the completely non-conservative limit of isotropic re-emission from the vicinity of the accretor, is shown to be able to form any pair of merging double COs, with the exception of WD + BH and with a limited parameter space for NS + NS. Considering the possibility of mass outflow from the Lagrangian point L2, the resulting parameter space for GW progenitors is shifted toward smaller initial mass ratios (defined as the ratio of the donor mass over the CO mass), consequently ruling out the formation of NS + NS pairs while allowing the production of merging WD + BH binaries. We compare our results with observations of single-degenerate binaries and find that the conditions for the stable MT channel to operate are present in nature. We then show that stable MT in the isotropic re-emission channel can produce merging binary BHs with mass ratios > 0.1, consistent with the majority of inferred sources of the third gravitational wave transient catalogue. Enhanced angular momentum loss from L2 increases the minimum final mass ratio achievable by stable MT.

Reconceptualizing merge in search for the link with brain oscillatory nature of language in biolinguistics

This brief piece argues that it is desirable to reconceptualize the syntactic combinatorial mechanism Merge as a higher-order function that takes two functions (= a selector function and its ‘argument’ function) and yields a composite function in the context of I-language. On this functional characterization of Merge, all of the elements involved in Merge are conceived as functions as well: lexical items (LIs) as input of Merge and syntactic objects (SOs) as both input and output of Merge. It is claimed that this perspective of Merge is a bridging step toward further facilitating the mesoscopic-level (= dynome-level) investigation of the brain oscillatory nature of human language in the field of biolinguistics. In this framework, I make the case that it would be possible to analyze the brain oscillatory nature of Merge by appealing to the mathematical operation of the Fourier transform (FT) to the extent that Merge-related brain oscillations as physical waves can be captured by complex exponential functions/trigonometric functions in the temporal domain.

Reconceptualizing merge in search for the link with brain oscillatory nature of language in biolinguistics

This brief piece argues that it is desirable to reconceptualize the syntactic combinatorial mechanism Merge as a higher-order function that takes two functions (= a selector function and its ‘argument’ function) and yields a composite function in the context of I-language. On this functional characterization of Merge, all of the elements involved in Merge are conceived as functions as well: lexical items (LIs) as input of Merge and syntactic objects (SOs) as both input and output of Merge. It is claimed that this perspective of Merge is a bridging step toward further facilitating the mesoscopic-level (= dynome-level) investigation of the brain oscillatory nature of human language in the field of biolinguistics. In this framework, I make the case that it would be possible to analyze the brain oscillatory nature of Merge by appealing to the mathematical operation of the Fourier transform (FT) to the extent that Merge-related brain oscillations as physical waves can be captured by complex exponential functions/trigonometric functions in the temporal domain.

RANCANGAN MEDIA PEMBELAJARAN BERUPA APLIKASI AUGMENTED REALITY BERBASIS ANDROID

Abstract-Augmented Reality (AR) is a technology that combines objects from the real world and virtual objects in real-time conditions. The merging of real and virtual objects occurs with the support of the right technology while the interactions that are carried out can occur using certain devices. AR is a breakthrough in the field of very sophisticated technology. Because with this technology we can make all abstract or virtual things look real or real. So that researchers apply the Waterfall Media AR Mobile Learning Method to be able to display 3D images and animations in class VIII math subjects, specifically geometric shapes including: blocks, balls, cones, cubes, pyramids, prisms, and tubes, Provides convenience for teachers to add insight into the use of AR learning media in increasing student motivation and interest in learning at SMP NEGERI 1 Bengkulu City. Provides convenience for teachers to add insight into the use of AR learning media in increasing student motivation and interest in learning at SMP NEGERI 1 Bengkulu City. Based on the results of testing the learning media application in the form of Android-based Augmented Reality application as expected based on the menu being tested.

The Implementation of Augmented Reality Based on Vuforia and Unity for Interactive Learning in Introducing Ragam Randang Objects

Augmented Reality (AR) is a technology that combines objects from the real world and virtual or virtual objects with real-time or direct conditions. The merging of real and virtual objects occurs because of the right technological support while the interactions that are carried out can occur using certain devices. AR is a variation of Virtual Environments (VE), better known as Virtual Reality (VR). This VR technology allows users to fully immerse themselves in a virtual environment. While Augmented Reality technology is developing very fast, many applications in Indonesia use AR technology. This study uses the waterfall system development method, where the research flow will follow the phases of the waterfall. This application is built using Unity and Vuforia. The purpose of this research is an interactive application to make it easier for students and museum visitors to understand augmented reality through mobile devices. So that museum visitors and students can see objects containing information interactively

GRB 211211A-like Events and How Gravitational Waves May Tell Their Origins

GRB 211211A is a rare burst with a genuinely long duration, yet its prominent kilonova association provides compelling evidence that this peculiar burst was the result of a compact binary merger. However, the exact nature of the merging objects, whether they were neutron star pairs, neutron star–black hole systems, or neutron star–white dwarf systems, remains unsettled. This Letter delves into the rarity of this event and the possibility of using current and next-generation gravitational wave detectors to distinguish between the various types of binary systems. Our research reveals an event rate density of for GRB 211211A-like gamma-ray bursts (GRBs), which, assuming GRB 211211A is the only example of such a burst, is significantly smaller than that of typical long- and short-GRB populations. We further calculated that if the origin of GRB 211211A is a result of a neutron star–black hole merger, it would be detectable with a significant signal-to-noise ratio (S/N), given the LIGO-Virgo-KAGRA designed sensitivity. On the other hand, a neutron star–white dwarf binary would also produce a considerable S/N during the inspiral phase at decihertz and is detectable by next-generation spaceborne detectors DECIGO and the Big Bang Observer. However, to detect this type of system with millihertz spaceborne detectors like LISA, Taiji, and TianQin, the event must be very close, approximately 3 Mpc in distance or smaller.

Generalizing Simultaneously to Support Smooth Zooming: Case Study of Merging Area Objects

When users zoom in or out on a digital map, the map should change correspondingly to present geographical information at proper levels. A way to help map users better keep track of their interested objects is to change the map smoothly instead of discretely switching between several levels of detail. This paper focuses on the problem of providing smooth merging of area objects. We propose to merge multiple areas simultaneously to share their animation durations. In this way, each merging operation can be prolonged, and it is visually smoother. We present a greedy algorithm to decide which areas should be merged at each step. The merging process is pre-computed and is recorded into a space-scale cube (SSC). When a user accesses our web map, the SSC is sent to the client side so that the map can be generated by slicing the SSC in the graphics processing unit (GPU). We also explain how to snap the zooming to valid states so that the zooming will not stop halfway of the merging operations. Our case study shows that it is visually smoother to merge simultaneously than to sequentially merge each pair of areas.

SCATTER: A New Common Envelope Formalism

One of the most mysterious astrophysical states is the common envelope (CE) phase of binary evolution, in which two stars are enshrouded by the envelope shed by one of them. Interactions between the stars and the envelope shrinks the orbit. The CE can lead to mergers or to a subsequent phase of interactions. Mergers may involve any combination of two compact objects and/or stars. Some involving white dwarfs may produce Type Ia supernovae, while merging neutron stars may yield gamma-ray bursts, and merging compact objects of all kinds produce gravitational radiation. Since CEs can arise from a variety of different initial conditions, and due to the complexity of the processes involved, it is difficult to predict their end states. When many systems are being considered, as in population synthesis calculations, conservation principles are generally employed. Here we use angular momentum in a new way to derive a simple expression for the final orbital separation. This method provides advantages for the study of binaries and is particularly well suited to higher-order multiples, now considered to be important in the genesis of potential mergers. Here we focus on CEs in binaries, and the follow-up paper extends our formalism to multiple-star systems within which a CE occurs.

Studying Postmerger Outflows from Magnetized-neutrino-cooled Accretion Disks

Neutrino-cooled accretion flow around a spinning black hole, produced by a compact binary merger, is a promising scenario for jet formation and launching magnetically driven outflows. Based on GW170817 gravitational wave detection by LIGO and Virgo observatories, followed by electromagnetic counterparts, this model can explain the central engine of the short-duration gamma-ray bursts and kilonova radiations. Using the open-source general relativistic magnetohydrodynamic HARM-COOL code, we evolved several 2D magnetized accretion disk–black hole models with a realistic equation of state in the fixed curved spacetime background. We applied the particle tracer technique to measure the properties of the outflows. The disk and black hole's initial parameters are chosen in a way to represent different possible postmerger scenarios of the merging compact objects. Our simulations show a strong correlation between the black hole's spin and ejected mass. Generally, mergers producing massive disks and rapidly spinning black holes launch stronger outflows. We observed our models generate winds with moderate velocity (v/c ∼ 0.1–0.2) and a broad range of electron fractions. We use these results to estimate the luminosity and light curves of possible radioactively powered transients emitted by such systems. We found that the luminosity peaks within the range of 1040–1042 erg s−1, which agrees with previous studies for disk wind outflows.

Counting states: A combinatorial analysis of SQM fragmentation

AbstractThe Strange Quark Matter (SQM) hypothesis states that at extreme pressure and density conditions, a new ground state of matter would arise, in which half of the down quarks become strange quarks. If true, it would mean that at least the core of neutron stars is made of SQM. In this hypothesis, SQM would be released in the interstellar medium when two of these objects merge. It is estimated that of SQM would be released this way. This matter will undergo a sequence of processes that should result in a fraction of the released SQM becoming heavy nuclei through the r‐process. In this work, we are interested in characterizing the fragmentation of SQM, with the novelty of keeping track of the quark configuration of the fragmented matter. This is accomplished by developing a methodology to estimate the energy of each fragment as the sum of its constituent quarks, the Coulomb interaction among the quarks and fragments' momenta.

Footprints of Population III Stars in the Gravitational-wave Background

We investigate detection prospects of the gravitational-wave background (GWB) that originates from the merging of compact objects formed by the collapse of Population III stars. Younger Population I/II stars lead to a GWB in the LIGO/Virgo frequency band at the inspiral phase, while Population III stars would likely show up at the later merger and ringdown phases. We show that, using a network of third-generation detectors, we may be able to separate a Population I/II signal from a Population III one, provided we can subtract individual coalescence events. A detection of a Population III GWB could reveal important information, such as the average redshifted total mass.

Fixing the BMS frame of numerical relativity waveforms with BMS charges

The Bondi-van der Burg-Metzner-Sachs (BMS) group, which uniquely describes the symmetries of asymptotic infinity and therefore of the gravitational waves that propagate there, has become increasingly important for accurate modeling of waveforms. In particular, waveform models, such as post-Newtonian (PN) expressions, numerical relativity (NR), and black hole perturbation theory, produce results that are in different BMS frames. Consequently, to build a model for the waveforms produced during the merging of compact objects, which ideally would be a hybridization of PN, NR, and black hole perturbation theory, one needs a fast and robust method for fixing the BMS freedoms. In this work, we present the first means of fixing the entire BMS freedom of NR waveforms to match the frame of either PN waveforms or black hole perturbation theory. We achieve this by finding the BMS transformations that change certain charges in a prescribed way -- e.g., finding the center-of-mass transformation that maps the center-of-mass charge to a mean of zero. We find that this new method is 20 times faster, and more correct when mapping to the superrest frame, than previous methods that relied on optimization algorithms. Furthermore, in the course of developing this charge-based frame fixing method, we compute the PN expression for the Moreschi supermomentum to 3PN order without spins and 2PN order with spins. This Moreschi supermomentum is effectively equivalent to the energy flux or the null memory contribution at future null infinity $\mathscr{I}^{+}$. From this PN calculation, we also compute oscillatory ($m\not=0$ modes) and spin-dependent memory terms that have not been identified previously or have been missing from strain expressions in the post-Newtonian literature.

MSAA-Net: a multi-scale attention-aware U-Net is used to segment the liver

Automatic segmentation of the liver from CT images is a very challenging task because the shape of the liver in the abdominal cavity varies from person to person and it also often fits closely with other organs. In recent years, with the continuous development of deep learning and the proposal of CNN, the neural network-based segmentation models have shown good performance in the field of image segmentation. Among the many network models, U-Net stands out in the task of medical image segmentation. In this paper, we propose a segmentation network MSAA-Net combining multi-scale features and an improved attention-aware U-Net. We extracted features of different scales on a single feature layer and performed attention perception in the channel dimension. We demonstrate that this architecture improves the performance of U-Net, while significantly reducing computational costs. To address the problem that U-Net’s skip connection is difficult to optimize for merging objects of different sizes, we designed a multi-scale attention gate structure (MAG), which allows the model to automatically learn to focus on targets of different sizes. In addition, MAG can be extended to all structures which contain skip connections, such as U-Net and FCN variants. Our structure was extensively evaluated on the 3Dircadb dataset, and the DICE similarity coefficient of the method for the liver segmentation task was 94.42%, with a much smaller number of model parameters than other attentional models. The experimental results show that MSAA-Net achieves very competitive performance in liver segmentation.

Harmonizing Full and Partial Matching in Geospatial Conflation: A Unified Optimization Model

Spatial data conflation is aimed at matching and merging objects in two datasets into a more comprehensive one. Starting from the “map assignment problem” in the 1980s, optimized conflation models treat feature matching as a natural optimization problem of minimizing certain metrics, such as the total discrepancy. One complication in optimized conflation is that heterogeneous datasets can represent geographic features differently. Features can correspond to target features in the other dataset either on a one-to-one basis (forming full matches) or on a many-to-one basis (forming partial matches). Traditional models consider either full matching or partial matches exclusively. This dichotomy has several issues. Firstly, full matching models are limited and cannot capture any partial match. Secondly, partial matching models treat full matches just as partial matches, and they are more prone to admit false matches. Thirdly, existing conflation models may introduce conflicting directional matches. This paper presents a new model that captures both full and partial matches simultaneously. This allows us to impose structural constraints differently on full/partial matches and enforce the consistency between directional matches. Experimental results show that the new model outperforms conventional optimized conflation models in terms of precision (89.2%), while achieving a similar recall (93.2%).

All analytic solutions for geodesic motion in axially symmetric space-times

Recent observations of the orbits of star clusters around Sgr A^star , imaging of black holes and gravitational waveforms of merging compact objects require a detailed understanding of the general relativistic geodesic motion. We came up with a method to provide all the possible geodesics in an axially symmetric space-time. The Kerr metric is explicitly worked out, recovering the Schwarzschild geodesics in the static limit. We also found the most general Killing tensor and its associated constant of motion for an axisymmetric space-time. The relevance of these results is crucial to understanding the different scenarios and the fundamental nature of the compact object at the galactic center.

Gravitational-wave echoes from numerical-relativity waveforms via spacetime construction near merging compact objects

We propose a new approach toward reconstructing the late-time near-horizon geometry of merging binary black holes, and toward computing gravitational-wave echoes from exotic compact objects. A binary black-hole merger spacetime can be divided by a time-like hypersurface into a Black-Hole Perturbation (BHP) region, in which the space-time geometry can be approximated by homogeneous linear perturbations of the final Kerr black hole, and a nonlinear region. At late times, the boundary between the two regions is an infalling shell. The BHP region contains late-time gravitational-waves emitted toward the future horizon, as well as those emitted toward future null infinity. In this region, by imposing no-ingoing wave conditions at past null infinity, and matching out-going waves at future null infinity with waveforms computed from numerical relativity, we can obtain waves that travel toward the future horizon. In particular, the Newman-Penrose $\psi_0$ associated with the in-going wave on the horizon is related to tidal deformations measured by fiducial observers floating above the horizon. We further determine the boundary of the BHP region on the future horizon by imposing that $\psi_0$ inside the BHP region can be faithfully represented by quasi-normal modes. Using a physically-motivated way to impose boundary conditions near the horizon, and applying the so-called Boltzmann reflectivity, we compute the quasi-normal modes of non-rotating ECOs, as well as gravitational-wave echoes. We also investigate the detectability of these echoes in current and future detectors, and prospects for parameter estimation.