Merger Time Research Articles

Black hole mergers from dwarf to massive galaxies with the NewHorizon and Horizon-AGN simulations

ABSTRACT Massive black hole (MBH) coalescences are powerful sources of low-frequency gravitational waves. To study these events in the cosmological context, we need to trace the large-scale structure and cosmic evolution of a statistical population of galaxies, from dim dwarfs to bright galaxies. To cover such a large range of galaxy masses, we analyse two complementary simulations: horizon-AGN with a large volume and low resolution that tracks the high-mass ($\gt 10^7\, {\rm M_\odot }$) MBH population, and NewHorizon with a smaller volume but higher resolution that traces the low-mass ( $\lt 10^7\, {\rm M_\odot }$) MBH population. While Horizon-AGN can be used to estimate the rate of inspirals for pulsar timing arrays, NewHorizon can investigate MBH mergers in a statistical sample of dwarf galaxies for LISA, which is sensitive to low-mass MBHs. We use the same method to analyse the two simulations, post-processing MBH dynamics to account for time delays mostly determined by dynamical friction and stellar hardening. In both simulations, MBHs typically merge long after galaxies do, so that the galaxy morphology at the time of the MBH merger is no longer determined by the structural disturbances engendered by the galaxy merger from which the MBH coalescence has originated. These time delays cause a loss of high-z MBH coalescences, shifting the peak of the MBH merger rate to z ∼ 1–2. This study shows how tracking MBH mergers in low-mass galaxies is crucial to probing the MBH merger rate for LISA and investigate the properties of the host galaxies.

How does perceived social support and self-esteem impact employees’ turnover intention? Case of banks’ merger in Pakistan

Objectives: Study indicates the importance of social support and employee personality dimension- self-esteem to counter withdrawal behaviours and help retain employees at the demanding time of mergers. Methods/Statistical analysis: Total 318 responses were collected from employees of Muslim Commercial Bank (MCB) undergoing a merger with NIB bank in Pakistan by using convenience sampling. Data was analyzed using a two-step method of PLS-SEM. Findings: The study found a positive relationship of perceived social support to self-esteem while negative relationship of self-esteem found with turnover intention. Furthermore, the relationship of perceived social support and turnover intention negatively mediated with indirect effect of self-esteem. Novelty: Study is unique in a sense that has incorporated employees’ own belief- self-esteem as an important mediating mechanism to reduce employee withdrawals during organizational changes. Keywords: Perceived social support; self-esteem; turnover intention; merger

Application of dictionary learning to denoise LIGO’s blip noise transients

Data streams of gravitational-wave detectors are polluted by transient noise features, or "glitches", of instrumental and environmental origin. In this work, we investigate the use of total-variation methods and learned dictionaries to mitigate the effect of those transients in the data. We focus on a specific type of transient, "blip" glitches, as this is the most common type of glitch present in the LIGO detectors and their waveforms are easy to identify. We randomly select 80 blip glitches scattered in the data from advanced LIGO's O1 run, as provided by the citizen-science project Gravity Spy. Our results show that dictionary-learning methods are a valid approach to model and subtract most of the glitch contribution in all cases analyzed, particularly at frequencies below $\sim 1$ kHz. The high-frequency component of the glitch is best removed when a combination of dictionaries with different atom length is employed. As a further example, we apply our approach to the glitch visible in the LIGO-Livingston data around the time of merger of binary neutron star signal GW170817, finding satisfactory results. This paper is the first step in our ongoing program to automatically classify and subtract all families of gravitational-wave glitches employing variational methods.

IceCube Search for Neutrinos Coincident with Compact Binary Mergers from LIGO-Virgo’s First Gravitational-wave Transient Catalog

Abstract Using the IceCube Neutrino Observatory, we search for high-energy neutrino emission coincident with compact binary mergers observed by the LIGO and Virgo gravitational-wave (GW) detectors during their first and second observing runs. We present results from two searches targeting emission coincident with the sky localization of each GW event within a 1000 s time window centered around the reported merger time. One search uses a model-independent unbinned maximum-likelihood analysis, which uses neutrino data from IceCube to search for pointlike neutrino sources consistent with the sky localization of GW events. The other uses the Low-Latency Algorithm for Multi-messenger Astrophysics, which incorporates astrophysical priors through a Bayesian framework and includes LIGO-Virgo detector characteristics to determine the association between the GW source and the neutrinos. No significant neutrino coincidence is seen by either search during the first two observing runs of the LIGO-Virgo detectors. We set upper limits on the time-integrated neutrino emission within the 1000 s window for each of the 11 GW events. These limits range from 0.02 to 0.7 . We also set limits on the total isotropic equivalent energy, E iso, emitted in high-energy neutrinos by each GW event. These limits range from 1.7 × 1051 to 1.8 × 1055 erg. We conclude with an outlook for LIGO-Virgo observing run O3, during which both analyses are running in real time.

Masses of double neutron star mergers

Aims. I aim to explain the mass discrepancy between the observed double neutron-star binary population by radio pulsar observations and gravitational-wave observation. Methods. I performed binary population synthesis calculations and compared their results with the radio and the gravitational-wave observations simultaneously. Results. Simulations of binary evolution were used to link different observations of double neutron star binaries with each other. I investigated the progenitor of GW190425 in more detail. A distribution of masses and merger times of the possible progenitors is presented. Conclusions. A mass discrepancy between the radio pulsars in the Milky Way with another neutron star companion and the inferred masses from gravitational-wave observations of those kind of merging systems is naturally found in binary evolution.

Bubble coalescence in electrolytes: Effect of bubble approach velocity

The coalescence of air bubbles in aqueous solutions of electrolytes was studied experimentally. The bubbles were produced from two vertical parallel capillaries in a still liquid and video recorded. Several quantities were evaluated: bubble shape and size, bubble distance, bubble expansion rate, time of the first touch, time of bubble merger, time of bubble detachment. The three state variables were: bubble coalescence efficiency E, transition electrolyte concentration Ct, bubble contact time T. The effect of four control parameters was investigated: electrolyte type (3 inorganic salts: NaCl, Na2SO4, CaCl2), electrolyte concentration C (5 values sparsely covering a broad interval, 0.001–2 mol/L), bubble approach velocity V (9 values, from 0.03 to 40 mm/s), bubble diameter D (2 values, 1 and 1.5 mm). The following results were obtained. Coalescence efficiency E decreases with both C and V. Transition concentration Ct is not a material property but depends on the hydrodynamic conditions, Ct decreases with V. Contact time T decreases with V, as T ∼ V−1, and increases with C, roughly as T ∼ C1.9. Bubble approach velocity V plays a dual role: it reduces the coalescence region but accelerates the coalescence process. The transition from coalescence to noncoalescence proceeds via a minimum in the T(V) graphs. Bubble size D reduces the value of Ct, whence the extent of the coalescence region. The three electrolytes behave in a similar way. A scale-estimates model was developed to describe the results. The effect of electrolytes on the coalescence is similar to the effect of liquid viscosity.

Science with the TianQin observatory: Preliminary results on stellar-mass binary black holes

We study the prospect of using TianQin to detect stellar-mass binary black holes (SBBHs). We estimate the expected detection number as well as the precision of parameter estimation on SBBH inspirals, using five different population models. We note TianQin can possibly detect a few SBBH inspirals with signal to noise ratios greater than 12; lowering the threshold and combining multiple detectors can both boost the detection number. The source parameters can be recovered with good precision for most events above the detection threshold. For example, the precision of the merger time most likely occurs near 1 s, making it possible to guide the detection of the ground-based detectors, the precision of the eccentricity ${e}_{0}$ most likely occurs near ${10}^{\ensuremath{-}4}$, making it possible to distinguish the formation channels, and the precision of the mass parameter is better than ${10}^{\ensuremath{-}6}$ in general and most likely occurs near ${10}^{\ensuremath{-}7}$. We note, in particular, that for a typical merger event, the error volume is likely to be small enough to contain only the host galaxy, which could greatly help in the study of gravitational wave cosmology and relevant studies through the multimessenger observation.

The Luminosity Distribution of Short Gamma-Ray Bursts under a Structured Jet Scenario

Abstract The joint detection of gravitational wave (GW) and electromagnetic radiation from the binary neutron star merger event GW170817 marks a breakthrough in the field of multi-messenger astronomy. The short gamma-ray burst (sGRB) GRB 170817A, associated with this binary neutron star merger event, has an isotropic-equivalent gamma-ray radiation luminosity of 1.6 × 1047 erg s−1, which is much lower than that of other sGRBs. The measurement of the superluminal movement of the radio afterglow emission confirms the presence of the relativistic jet, and the emission features can be well explained by the structured jet model. In this paper, we calculate the luminosity distribution of sGRBs and its evolution with redshift based on the structured (Gaussian) jet model, and find that the typical luminosity increase with redshift, for nearby sGRBs (such as for luminosity distance less than 200 Mpc) the typical gamma-ray luminosity is just around 1047–1048 erg s−1, which naturally explains the very low radiation luminosity of GRB 170817A. We derived the detection probability of sGRBs by Fermi-GBM and found that the expected detection rate of sGRBs is only about 1 yr−1 within the distance of several hundred Mpc. We explored the effect of the power-law index α of the merger time distribution on the observed characteristics and found that it had little effect on the observed luminosity and viewing-angle distributions. However, it is very interesting that, for different values of α, the distributions of the number of observed sGRBs are quite different, so it is possible to determine the value of α through observed distributions of the number of sGRBs. We used the Bayesian method to make a quantitative analysis and found that the value of α may be identified when the number of observed sGRBs with known redshifts is more than 200. Finally, we compare our results of gamma-ray luminosity distribution with sGRBs with known redshifts, and found that our results are consistent with the observation, which implies that our simulation results can reproduce the observed luminosity distribution well.

OPTIMAL TIMING AND TERMS IN A VERTICAL MERGER WITH TWO SOURCES OF UNCERTAINTY

AbstractIn this article we provide the optimal timing and equilibrium terms of a vertical merger with two sources of uncertainty in the production chain, namely, marginal cost of raw material and price level of final product. By eliminating monopoly power and transaction cost in the production process between upstream and downstream firms, a vertical merger can increase social welfare, which is consistent with the literature. The optimal threshold of a vertical merger is negatively correlated with transaction cost in the intermediate product market. Vertical mergers also accelerate when merging provides natural hedging for the postmerger firm, that is, when the correlation between the two uncertainties increases.

A Toy Model for the Electromagnetic Output of Neutron-star Merger Prompt Collapse to a Black Hole: Magnetized Neutron-star Collisions

Abstract We present a systematic study of magnetized neutron star head-on collisions. We investigate the resulting magnetic field geometries as the two neutron stars merge. Furthermore, we analyze the luminosity produced in these collisions and monitor the evolution of the magnetic fields from the time of merger until the subsequent production of a black hole. At the time of black hole formation, the luminosity peaks and rings down following the decay of the electromagnetic fields. A comparison is presented for three different cases: one where the initial magnetic field in both neutron stars is aligned, one where they are anti-aligned, and one where they initially have unequal magnetic field strength. We identify regions and set limits so that pair creation and magnetic reconnection would occur in this scenario and further discuss limits and differences in the radiated energy. This study should be regarded as a toy model of the case where the remnant of a binary neutron star merger undergoes a prompt collapse to a black hole with a negligible surrounding disk. We note that the generated electromagnetic pulses resemble the fast radio burst phenomenology. We consider implications of the high-mass mergers leading to a fast prompt collapse to a black hole and the expected flux to be observed at a distance similar to the binary neutron star gravitational wave detection GW190425.

LISA and the Existence of a Fast-merging Double Neutron Star Formation Channel

Abstract Using a Milky Way (MW) double neutron star (DNS) merger rate of 210 Myr−1, as derived by the Laser Interferometer Gravitational-Wave Observatory (LIGO), we demonstrate that the Laser Interferometer Space Antenna (LISA) will detect on average 240 (330) DNSs within the MW for a 4 yr (8 yr) mission with a signal-to-noise ratio greater than 7. Even adopting a more pessimistic rate of 42 Myr−1, as derived by the population of Galactic DNSs, we find a significant detection of 46 (65) MW DNSs. These DNSs can be leveraged to constrain formation scenarios. In particular, without prior information on a particular system’s position and orbital period, traditional NS-discovery methods using radio telescopes alone are insensitive to DNSs with P orb ≲ 1 hr (merger times ≲10 Myr). If a fast-merging channel exists that forms DNSs at these short orbital periods, LISA affords, perhaps, the best opportunity to observationally identify and characterize these systems; we show that toy models for possible formation scenarios leave imprints on DNS orbital eccentricities, which may be measured by LISA for values as small as ∼10−2.

Fast Radio Bursts from Activity of Neutron Stars Newborn in BNS Mergers: Offset, Birth Rate, and Observational Properties

Abstract Young neutron stars (NSs) born in core-collapse explosions are promising candidates for the central engines of fast radio bursts (FRBs), since the first localized repeating burst FRB 121102 occurs in a star-forming dwarf galaxy similar to the host galaxies of superluminous supernovae and long gamma-ray bursts. However, FRB 180924 and FRB 190523 are localized to massive galaxies with low rates of star formation, compared with the host of FRB 121102. The offsets between the bursts and host centers are about 4 and 29 kpc for FRB 180924 and FRB 190523, respectively. These host properties are similar to those of short gamma-ray bursts (GRBs), which are produced by binary neutron star (BNS) or NS–black hole mergers. Therefore, the NSs powering FRBs may be formed in BNS mergers. In this paper, we study BNS merger rates and merger times, and predict the most likely merger locations for different types of host galaxies using the population synthesis method. We find that the BNS merger channel is consistent with the recently reported offsets of FRB 180924 and FRB 190523. The offset distribution of short GRBs is well reproduced by population synthesis using a galaxy model similar to that of GRB hosts. The event rate of FRBs (including non-repeating and repeating), is larger than those of BNS mergers and short GRBs, and requires a large fraction of observed FRBs emitting several bursts. Using curvature radiation by bunches in NS magnetospheres, we also predict the observational properties of FRBs from BNS mergers, including the dispersion measure and rotation measure. At late times (t ≥ 1 yr), the contribution to dispersion measure and rotation measure from BNS merger ejecta can be neglected.

Determinants of initial goodwill overstatement in affiliated and non‐affiliated mergers

AbstractThis study examines the determinants of goodwill overstatement at the time of mergers in a Korean setting. In the Korean M&A market, there are two types of mergers: mergers between independent companies (non‐affiliated mergers) and mergers between companies under common control (affiliated mergers). This study extends the literature by examining the factors likely to cause goodwill overstatement in both types of mergers. The results reveal that in affiliated mergers, goodwill at the time of a merger tends to be overstated when controlling owners have higher equity ownership in the target than in the acquirer. By contrast, information uncertainty in the target value causes initial goodwill overstatement in non‐affiliated mergers. We also find that monitoring of independent institutional investors with concentrated holdings against overpaying for the target is more pronounced when controlling owners in affiliated mergers have incentives to overpay for the target. In affiliated mergers, acquirers tend to write off goodwill more frequently when controlling owners have higher equity ownership in the target than in the acquirer. In non‐affiliated mergers, information uncertainty in the target value is significantly associated with subsequent goodwill write‐offs. These results suggest that the type of merger has important consequences for initial goodwill recognition and subsequent impairment.

NGC 4993, the shell galaxy host of GW170817: constraints on the recent galactic merger

Context. NGC 4993 is the shell galaxy host of the GRB170817A short gamma-ray burst and the GW170817 gravitational-wave event produced during a binary-neutron-star coalescence. Aims. The galaxy shows signs, including the stellar shells, that it has recently accreted a smaller, late-type galaxy. The accreted galaxy might be the original host of the binary neutron star. Methods. We measured the positions of the stellar shells of NGC 4993 in an HST/ACS archival image and use the shell positions to constrain the time of the galactic merger. Results. According to the analytical model of the evolution of the shell structure in the expected gravitational potential of NGC 4993, the galactic merger happened at least 200 Myr ago, with a probable time roughly around 400 Myr, and the estimates higher than 600 Myr being improbable. This constitutes the lower limit on the age of the binary neutron star, because the host galaxy was probably quenched even before the galactic merger, and the merger has likely shut down the star formation in the accreted galaxy. We roughly estimate the probability that the binary neutron star originates in the accreted galaxy to be around 30%.

An Analytical Study of Impact of International Merger and Acquisitions on the Financial Performance for Higher Education Institution in the United States

The paper summarizes the arguments and counterarguments within the scientific discussion on the issues such as higher education institutions, mergers and acquisitions, world class universities, integrated postsecondary educational data system in the United States. The main purpose of this scientific research study problem is the impact of international merger and acquisition on the financial performance for higher education institution in the United States. Synthesis of this topic has a significant impact on the financial well-being for all students and professors around the World. The methodology is the observation then synthesis all current and prior existing literature and facts available for the purpose of understanding the current financial situation for all higher education industry. The paper presents the results of a critical thinking analysis integrated postsecondary education data system. The U.S. Department of Education’s National Center for Education Statistics for higher education institutions database system, called the Integrated Postsecondary Education Data System. This U.S. Government run database has collected annual higher education institutions level information since 1986 and by statute requires all Title IV higher education institutions to report in an accurate and timely manner to this database. This research contributed to the advancement of scientific knowledge in that it provided a research study on the interaction effects between time and merger status upon the performance metrics which generalize across regional, state, and national landscapes. Practical implications address how interested higher education institutions stakeholders can use this study to analyze the historical interaction effects between merger status and time on performance metrics which they wish to improve. The future implications discussion includes how this research study provided what researchers in the field have asked for and how this increased knowledge of merger and acquisitions longitudinal effects on performance metrics provides a framework for further study in this area. Keywords: merger, acquisitions, higher education institutions, revenues.

Impact of a Spinning Supermassive Black Hole on the Orbit and Gravitational Waves of a Nearby Compact Binary

Abstract Recent theoretical studies suggest that stellar-mass binary black holes (BBHs) would merge more efficiently due to the Kozai–Lidov (K–L) mechanism if these binaries form in the vicinity of supermassive black holes (SMBHs). Since SMBHs are likely rotating rapidly, we continue our earlier study on the generalization of the K–L formalism to include the spin of the SMBH and study the evolution of a nearby BBH. We find that the eccentricity and orbital inclination of the BBH are significantly affected, because the spin (i) forces the orbital plane of the center-of-mass of the BBH around the SMBH to precess (the Lense–Thirring effect) and (ii) imposes an additional gravitomagnetic force on the BBH. As a result, the merger time of the BBH could be significantly different. We calculate the waveform from the BBH in one representative example and study its detectability with a milli-Hertz gravitational-wave detector, such as the Laser Interferometer Space Antenna (LISA). We find that the signal is distinguishable from that in the case without spin. Our results imply that the BBHs in the LISA band could potentially be used to probe the spin of the SMBHs in galaxy centers.

On the Mass Assembly History of the Local Group

Abstract In this work an ensemble of simulated Local Group analogues is used to constrain the properties of the mass assembly history of the Milky Way (MW) and Andromeda (M31) galaxies. These objects have been obtained using the constrained simulation technique, which ensures that simulated LGs live within a large scale environment akin to the observed one. Our results are compared against a standard Λ Cold Dark Matter (ΛCDM) series of simulations which use the same cosmological parameters. This allows us to single out the effects of the constraints on the results. We find that (a) the median constrained merging histories for M31 and MW live above the standard ones at the 1-σ level, (b) the median formation time takes place ≈0.5 Gyr earlier than unconstrained values, while the latest major merger happens on average 1.5 Gyr earlier and (c) the probability for both LG haloes to have experienced their last major merger in the first half of the history of the Universe is $\approx 50\%$ higher for the constrained pairs. These results have been estimated to be significant at the $99\%$ confidence level by means of a Kolmogorov-Simirnov test. These results suggest that the particular environment in which the Milky Way and Andromeda form plays a role in shaping their properties, and favours earlier formation and last major merger time values in agreement with other observational and theoretical considerations.

GROWTH on S190425z: Searching Thousands of Square Degrees to Identify an Optical or Infrared Counterpart to a Binary Neutron Star Merger with the Zwicky Transient Facility and Palomar Gattini-IR

Abstract The third observing run by LVC has brought the discovery of many compact binary coalescences. Following the detection of the first binary neutron star merger in this run (LIGO/Virgo S190425z), we performed a dedicated follow-up campaign with the Zwicky Transient Facility (ZTF) and Palomar Gattini-IR telescopes. The initial skymap of this single-detector gravitational wave (GW) trigger spanned most of the sky observable from Palomar Observatory. Covering 8000 deg2 of the initial skymap over the next two nights, corresponding to 46% integrated probability, ZTF system achieved a depth of ≈21 m AB in g- and r-bands. Palomar Gattini-IR covered 2200 square degrees in J-band to a depth of 15.5 mag, including 32% integrated probability based on the initial skymap. The revised skymap issued the following day reduced these numbers to 21% for the ZTF and 19% for Palomar Gattini-IR. We narrowed 338,646 ZTF transient “alerts” over the first two nights of observations to 15 candidate counterparts. Two candidates, ZTF19aarykkb and ZTF19aarzaod, were particularly compelling given that their location, distance, and age were consistent with the GW event, and their early optical light curves were photometrically consistent with that of kilonovae. These two candidates were spectroscopically classified as young core-collapse supernovae. The remaining candidates were ruled out as supernovae. Palomar Gattini-IR did not identify any viable candidates with multiple detections only after merger time. We demonstrate that even with single-detector GW events localized to thousands of square degrees, systematic kilonova discovery is feasible.

Black hole–neutron star mergers from triples – II. The role of metallicity and spin–orbit misalignment

ABSTRACT Observations of black hole–neutron star (BH–NS) mergers via gravitational waves (GWs) are of great interest for their electromagnetic counterparts, such as short gamma-ray bursts, and could provide crucial information on the nature of BHs and the NS crust and magnetosphere. While no event has been confirmed, a recent possible detection of a BH–NS merger event by the LIGO–Virgo collaboration has attracted a lot of attention to these sources. In this second paper of the series, we follow-up our study of the dynamical evolution of triples composed of an inner BH–NS binary. In particular, we examine how the progenitor metallicity affects the characteristics of the BH–NS mergers in triples. We determine the distributions of masses, orbital parameters, and merger times, as a function of the progenitor metallicity and initial triple orbital distributions, and show that the typical eccentricity in the LIGO band is ∼10−2–10−1. We derive a merger rate range of ΓBH–NS = 1.9 × 10−4–22 Gpc−3 yr−1, consistent the LIGO–Virgo upper limit. Finally, we study the expected spin–orbit misalignments of merging BH–NS binaries from this channel, and find that typically the effective spin distribution is peaked at χeff ∼ 0 with significant tails.

3D SIMULATION OF THE THERMAL REGIME OF A GROUP OF GAS WELLS IN THE SREDNETYUNGSKOE FIELD

The thermal interaction between a group of gas wells and the permafrost ground was simulated using the finite element method for the conditions of the Srednetyungskoe field. For the spacings between the wellheads of 10 m, 15 m, and 20 m, thermal regimes for the gas and surrounding ground massif are forecasted for 30 years of operation. The feature of the present work is that atmospheric conditions and the effect of the wells are modeled simultaneously in 3D, allowing for accurate characterization of the wellhead area. Field data on the ground temperature, the bottomhole pressure and temperature, the production rate, the gas composition, thermophysical properties of the ground, and weather conditions are used as input parameters. Temperature profiles of the ground, the position of the thawing front, and timing of merger of the thawing halos around the wells are estimated. The results of the survey can be used in development planning of the field.