Delay Time Distribution Research Articles

A 4 per cent measurement of H0 using the cumulative distribution of strong lensing time delays in doubly imaged quasars

ABSTRACT In the advent of large-scale surveys, individually modelling strong gravitational lenses and their counterpart time delays in order to precisely measure H0 will become computationally expensive and highly complex. A complimentary approach is to study the cumulative distribution function (CDF) of time delays where the global population of lenses is modelled along with H0. In this paper, we use a suite of hydrodynamical simulations to estimate the CDF of time delays from doubly imaged quasars for a realistic distribution of lenses. We find that the CDFs exhibit large amounts of halo–halo variance, regulated by the density profile inner slope and the total mass within 5 kpc. With the objective of fitting to data, we compress the CDFs using principal component analysis and fit a Gaussian processes regressor consisting of three physical features: the redshift of the lens, $z$L; the power-law index of the halo, α, and the mass within 5 kpc, plus four cosmological features. Assuming a flat Universe, we fit our model to 27 doubly imaged quasars finding $H_0=71^{+2}_{-3}$ km s−1 Mpc−1, $z_{\rm L}= 0.36_{-0.09}^{+0.2}$, $\alpha =-1.8_{-0.1}^{+0.1}$, log (M(< 5 kpc$)/M_\odot)=11.1_{-0.1}^{+0.1}$, $\Omega _{\rm M} = 0.3_{-0.04}^{+0.04}$, and $\Omega _{\rm \Lambda }=0.7_{-0.04}^{+0.04}$. We compare our estimates of $z$L and log (M(< 5 kpc)/M⊙) to the data and find that within the sensitivity of the data, they are not systematically biased. We generate mock CDFs and find with that the Vera Rubin Observatory (VRO) could measure σ/H0 to ${\lt}3{\rm {per \, cent}}$, limited by the precision of the model. If we are to exploit fully VRO, we require simulations that sample a larger proportion of the lens population, with a variety of feedback models, exploring all possible systematics.

Discovery of the Optical Afterglow and Host Galaxy of Short GRB 181123B at z = 1.754: Implications for Delay Time Distributions

Abstract We present the discovery of the optical afterglow and host galaxy of the Swift short-duration gamma-ray burst (SGRB) GRB 181123B. Observations with Gemini-North starting ≈9.1 hr after the burst reveal a faint optical afterglow with i ≈ 25.1 mag at an angular offset of 0.″59 ± 0.″16 from its host galaxy. Using grizYJHK observations, we measure a photometric redshift of the host galaxy of . From a combination of Gemini and Keck spectroscopy of the host galaxy spanning 4500–18000 Å, we detect a single emission line at 13390 Å, inferred as Hβ at z = 1.754 ± 0.001 and corroborating the photometric redshift. The host galaxy properties of GRB 181123B are typical of those of other SGRB hosts, with an inferred stellar mass of ≈9.1 × 109 M ⊙, a mass-weighted age of ≈0.9 Gyr, and an optical luminosity of ≈0.9L*. At z = 1.754, GRB 181123B is the most distant secure SGRB with an optical afterglow detection and one of only three at z > 1.5. Motivated by a growing number of high-z SGRBs, we explore the effects of a missing z > 1.5 SGRB population among the current Swift sample on delay time distribution (DTD) models. We find that lognormal models with mean delay times of ≈4–6 Gyr are consistent with the observed distribution but can be ruled out to 95% confidence, with an additional ≈one to five Swift SGRBs recovered at z > 1.5. In contrast, power-law models with ∝t −1 are consistent with the redshift distribution and can accommodate up to ≈30 SGRBs at these redshifts. Under this model, we predict that ≈1/3 of the current Swift population of SGRBs is at z > 1. The future discovery or recovery of existing high-z SGRBs will provide significant discriminating power on their DTDs and thus their formation channels.

Mean-square consensus for heterogeneous multi-agent systems with probabilistic time delay

This paper studies the delay-dependent consensus problem of heterogeneous multi-agent systems over directed topology. The heterogeneous dynamics consisting of both first-order and second-order agents with random time delay are considered. New distributed control protocols based on the probability distribution of time delay are proposed for the leader-following and leaderless systems. By adopting matrix theory, Lyapunov-Krasovskii function and stochastic analysis, some less conservative conditions for the mean-square consensus are established over directed fixed topology and switching topologies. Moreover, the larger upper bounds of time delay are obtained. Finally, several simulations are presented to illustrate the obtained results.

Delay-time Distributions of Solar Energetic Particles. II. Effects of Magnetic Focusing

Abstract We extend a recently published analytic model for the intensity–time profile of solar energetic particle (SEP) events, in which the dominant physical mechanism is turbulent pitch-angle scattering of a collimated distribution of particles accelerated at the Sun. The present model includes the effect of magnetic focusing in the expanding magnetic field geometry of the inner heliosphere. For a power-law variation of the magnetic field strength with distance (B ∼ s −α ) that lacks a characteristic focusing length scale, the fundamental shape of the intensity–time profile (i.e., a Lévy distribution at times up to and just past the time of peak intensity, followed by an exponential decay) is preserved. The effect of magnetic focusing is essentially to produce a rescaling of the stochastic process describing the angular diffusion of the particles, making the typical time that characterizes the SEP time profile quantitatively lower by a factor of (α + 1), 3 for the radial field geometry B ∼ s −2.

Pushing Cherenkov PET with BGO via coincidence time resolution classification and correction

Bismuth germanate (BGO) shows good properties for positron emission tomography (PET) applications, but was substituted by the development of faster crystals like lutetium oxyorthosilicate (LSO) for time-of-flight PET (TOF-PET). Recent improvements in silicon photomultipliers (SiPMs) and fast readout electronics make it possible to access the Cherenkov photon signal produced upon 511 keV interaction, which makes BGO a cost-effective candidate for TOF-PET.Tails in the time-delay distribution, however, remain a challenge. These are mainly caused by the high statistical fluctuation on the Cherenkov photons detected. To select fast events with a high detected Cherenkov photon number, the signal rise time of the SiPM was used for discrimination. The charge, time delay and signal rise time was measured for two different lengths of BGO crystals coupled to FBK NUV-HD SiPMs and high frequency readout in a coincidence time resolution setup. The recorded events were divided into 5 × 5 categories based on the signal rise time, and time resolutions of 200 ± 3 ps for 2 × 2 × 20 mm3 and 117 ± 3 ps for 2 × 2 × 3 mm3 were measured for the fastest 20% of the events (4% in coincidence). These good timing events can provide additional information for the image reconstruction in order to increase the SNR significantly, without spoiling the detector sensitivity. Putting all photopeak events together and correcting for the time bias introduced by different numbers of Cherenkov photons detected, time resolutions of 259 ± 3 ps for 20 mm long and 151 ± 3 ps for 3 mm long crystals were measured. For a small fraction of events sub-100 ps coincidence time resolution with BGO was reached for a 3 mm short pixel.

Shouts and Murmurs: Combining Individual Gravitational-wave Sources with the Stochastic Background to Measure the History of Binary Black Hole Mergers

Abstract One of the goals of gravitational-wave astronomy is to quantify the evolution of the compact binary merger rate with redshift. The redshift distribution of black hole mergers would offer considerable information about their evolutionary history, including their progenitor formation rate, the dependence of black hole formation on stellar metallicity, and the time delay distribution between formation and merger. Efforts to measure the binary redshift distribution are currently limited, however, by the detection range of existing instruments, which can individually resolve compact binary merger events only out to . We present a novel strategy with which to measure the redshift distribution of binary black hole mergers well beyond the detection range of current instruments. By synthesizing direct detections of individually resolved mergers with indirect searches for the stochastic gravitational-wave background due to unresolved distant sources, we can glean information about the peak redshift, z p , at which the binary black hole merger rate attains its maximum, even when this redshift is beyond the detection horizon. Using data from Advanced LIGO and Virgo’s first and second observing runs, we employ this strategy to place joint constraints on z p and the slope α with which the binary merger rate increases at low redshifts, ruling out merger rates that grow faster than and peak beyond . Looking ahead, we project that approximately one year of observation with design-sensitivity Advanced LIGO will further break remaining degeneracies, enabling a direct measurement of the peak redshift of the binary black hole merger history.

Imprints of the redshift evolution of double neutron star merger rate on the signal-to-noise ratio distribution

ABSTRACT Proposed third-generation gravitational wave interferometers such as Cosmic Explorer (CE) will have the sensitivity to observe double neutron star mergers (DNS) up to a redshift of ∼5 with good signal-to-noise ratios (SNRs). We argue that the comoving spatial distribution of DNS mergers leaves a unique imprint on the statistical distribution of SNRs of the detected DNS mergers. Hence, the SNR distribution of DNS mergers will facilitate a novel probe of their redshift evolution independent of the luminosity distance measurements. We consider detections of DNS mergers by the CE and study the SNR distribution for different possible redshift evolution models of DNSs and employ Anderson Darling p-value statistic to demonstrate the distinguishability between these different models. We find that a few hundreds of DNS mergers in the CE era will allow us to distinguish between different models of redshift evolution. We further apply the method for various SNR distributions arising due to different merger delay-time and star formation rate (SFR) models and show that for a given SFR model, the SNR distributions are sensitive to the delay-time distributions. Finally, we investigate the effects of sub-threshold events in distinguishing between different merger rate distribution models.

Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia

BackgroundThe initial cases of novel coronavirus (2019-nCoV)–infected pneumonia (NCIP) occurred in Wuhan, Hubei Province, China, in December 2019 and January 2020. We analyzed data on the first 425 confirmed cases in Wuhan to determine the epidemiologic characteristics of NCIP.MethodsWe collected information on demographic characteristics, exposure history, and illness timelines of laboratory-confirmed cases of NCIP that had been reported by January 22, 2020. We described characteristics of the cases and estimated the key epidemiologic time-delay distributions. In the early period of exponential growth, we estimated the epidemic doubling time and the basic reproductive number.ResultsAmong the first 425 patients with confirmed NCIP, the median age was 59 years and 56% were male. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days (95% confidence interval [CI], 4.1 to 7.0), with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days. With a mean serial interval of 7.5 days (95% CI, 5.3 to 19), the basic reproductive number was estimated to be 2.2 (95% CI, 1.4 to 3.9).ConclusionsOn the basis of this information, there is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019. Considerable efforts to reduce transmission will be required to control outbreaks if similar dynamics apply elsewhere. Measures to prevent or reduce transmission should be implemented in populations at risk. (Funded by the Ministry of Science and Technology of China and others.)

Effect of interpopulation spike-timing-dependent plasticity on synchronized rhythms in neuronal networks with inhibitory and excitatory populations.

We consider a two-population network consisting of both inhibitory (I) interneurons and excitatory (E) pyramidal cells. This I-E neuronal network has adaptive dynamic I to E and E to I interpopulation synaptic strengths, governed by interpopulation spike-timing-dependent plasticity (STDP). In previous works without STDPs, fast sparsely synchronized rhythms, related to diverse cognitive functions, were found to appear in a range of noise intensity D for static synaptic strengths. Here, by varying D, we investigate the effect of interpopulation STDPs on fast sparsely synchronized rhythms that emerge in both the I- and the E-populations. Depending on values of D, long-term potentiation (LTP) and long-term depression (LTD) for population-averaged values of saturated interpopulation synaptic strengths are found to occur. Then, the degree of fast sparse synchronization varies due to effects of LTP and LTD. In a broad region of intermediate D, the degree of good synchronization (with higher synchronization degree) becomes decreased, while in a region of large D, the degree of bad synchronization (with lower synchronization degree) gets increased. Consequently, in each I- or E-population, the synchronization degree becomes nearly the same in a wide range of D (including both the intermediate and the large D regions). This kind of "equalization effect" is found to occur via cooperative interplay between the average occupation and pacing degrees of spikes (i.e., the average fraction of firing neurons and the average degree of phase coherence between spikes in each synchronized stripe of spikes in the raster plot of spikes) in fast sparsely synchronized rhythms. Finally, emergences of LTP and LTD of interpopulation synaptic strengths (leading to occurrence of equalization effect) are intensively investigated via a microscopic method based on the distributions of time delays between the pre- and the post-synaptic spike times.

Delay Time Distributions of Type Ia Supernovae from Galaxy and Cosmic Star Formation Histories

Abstract We present analytical reconstructions of SN Ia delay time distributions (DTDs) by way of two independent methods: by a Markov Chain Monte Carlo best-fit technique comparing the volumetric SN Ia rate history to today’s compendium cosmic star formation history, and second through a maximum likelihood analysis of the star formation rate histories of individual galaxies in the GOODS/CANDELS field, in comparison to their resultant SN Ia yields. We adopt a flexible skew-normal DTD model, which could match a wide range of physically motivated DTD forms. We find a family of solutions that are essentially exponential DTDs, similar in shape to the β ≈ −1 power-law DTDs, but with more delayed events (>1 Gyr in age) than prompt events (<1 Gyr). Comparing these solutions to delay time measures separately derived from field galaxies and galaxy clusters, we find the skew-normal solutions can accommodate both without requiring a different DTD form in different environments. These model fits are generally inconsistent with results from single-degenerate binary population synthesis models, and are seemingly supportive of double-degenerate progenitors for most SN Ia events.

Constraining Type Iax supernova progenitor systems with stellar population age dating

ABSTRACT Type Iax supernovae (SNe Iax) are the most common class of peculiar SNe. While they are thought to be thermonuclear white-dwarf (WD) SNe, SNe Iax are observationally similar to, but distinct from SNe Ia. Unlike SNe Ia, where roughly 30 per cent occur in early-type galaxies, only one SN Iax has been discovered in an early-type galaxy, suggesting a relatively short delay time and a distinct progenitor system. Furthermore, one SN Iax progenitor system has been detected in pre-explosion images with its properties consistent with either of two models: a short-lived (<100 Myr) progenitor system consisting of a WD primary and a He-star companion, or a singular Wolf–Rayet progenitor star. Using deep Hubble Space Telescope images of nine nearby SN Iax host galaxies, we measure the properties of stars within 200 pc of the SN position. The ages of local stars, some of which formed with the SN progenitor system, can constrain the time between star formation and SN, known as the delay time. We compare the local stellar properties to synthetic photometry of single-stellar populations, fitting to a range of possible delay times for each SN. With this sample, we uniquely constrain the delay-time distribution for SNe Iax, with a median and 1σ confidence interval delay time of $63_{- 15}^{+ 58} \times 10^{6}$ yr. The measured delay-time distribution provides an excellent constraint on the progenitor system for the class, indicating a preference for a WD progenitor system over a Wolf–Rayet progenitor star.

The Distribution of Time Delays Between Nanoflares in Magnetohydrodynamic Simulations

Nanoflares are thought to be an important energy source for heating the solar corona. The exact amount of heating contributed by nanoflares depends, in part, on the frequency of the heating and the time interval between nanoflares. Several numerical models have attempted to constrain the frequency of the heating by fitting to observed emission measures. To date, however, no physically motivated value for the time interval between nanoflares has been obtained. In this paper, we calculate a physically motivated distribution of time intervals between successive “nanoflare” reconnection events in driven magnetohydrodynamic simulations. We show that this distribution follows a power law with a slope near −1, much shallower than previously inferred from observations and determined from loop model comparisons with observations. We show that the energy flux injected into the corona in our model is of order $10^{7}~\text{erg}\,\text{cm}^{-2}\,\text{s}^{-1}$, and that the heating rate due to these reconnection events reaches values of order $1\mbox{--}10~\text{erg}\,\text{cm}^{-3}\,\text{s}^{-1}$. Additionally, we show that this power law slope is dependent only weakly on the amount of magnetic helicity injected into the solar magnetic field by the photospheric motions, but the rate of reconnection is about $45\%$ higher if no magnetic helicity is injected.

Hot subdwarf B stars with neutron star components

Context. Subdwarf B stars (sdBs) play a crucial role in stellar evolution, asteroseismology, and far-UV radiation of early-type galaxies, and have been intensively studied with observation and theory. It has theoretically been predicted that sdBs with neutron star (NS) companions exist in the Galaxy, but none have been discovered yet. This remains a puzzle in this field. In a previous study (hereafter Paper I), we have studied the formation channels of sdB+NS binaries from main-sequence (MS) stars plus NS binaries by establishing a model grid, but it is still unclear how these binaries consisting of MS stars and NS binaries came to be in the first place. Aims. We systematically study the formation of sdB+NS binaries from their original zero-age main-sequence progenitors. We bridge the gap left by our previous study in this way. We obtain the statistical population properties of sdB+NS binaries and provide some guidance for observational efforts. Methods. We first used Hurley’s rapid binary evolution code BSE to evolve 107 primordial binaries to the point where the companions of NS+MS, NS+Hertzsprung gap star, and NS+Giant Branch star binaries have just filled their Roche lobes. Next, we injected these binaries into the model grid we developed in Paper I to obtain the properties of the sdB+NS populations. We adopted two prescriptions of NS natal kicks: the classical Maxwellian distribution with a dispersion of σ = 265 km s−1, and a linear formula that assumes that the kick velocity is associated with the ratio of ejected to remnant mass. Different values of αCE, where αCE is the common-envelope ejection efficiency, were chosen to examine the effect of common-envelope evolution on the results. Results. In the Galaxy, the birthrate of sdB+NS binaries is about 10−4 yr−1 and there are ∼7000 − 21 000 such binaries. This contributes 0.3−0.5% of all sdB binaries in the most favorable case. Most Galactic sdB+NS binaries (≳60%) arise from the channel of stable mass transfer. The value of αCE has little effect on the results, but when we use the linear formula prescription of NS natal kick, the number and birthrate doubles in comparison to the results we obtained with the Maxwellian distribution. The orbital periods of sdB+NS binaries from different formation channels differ significantly, as expected. This results in two peaks in the radial velocity (RV) semi-amplitude distribution: 100 − 150 km s−1 for stable mass transfer, and 400 − 600 km s−1 for common-envelope ejection. However, the two sdB+NS binary populations exhibit similar delay-time distributions, which both peak at about 0.2 Gyr. This indicates that Galactic sdB+NS binaries are born in very young populations, probably in the Galactic disk. The sdB+NS binaries produced from the common-envelope ejection channel are potential sources of strong gravitational wave radiation (GWR), and about ∼100 − 300 could be detected by the Laser Interferometer Space Antenna (LISA) with a signal-to-noise ratio of 1. Conclusions. Most sdB+NS binaries are located in the Galactic disk with small RV semi-amplitudes. SdB+NS binaries with large RV semi-amplitudes are expected to be strong GWR sources, some of which could be detected by LISA in the future.

Multi-channel photonic bandgap consequences in one-dimensional linear, exponential, and hyperbolic graded-index photonic crystals

We present the structuring of different graded-index materials in the form of one-dimensional (1D) photonic crystals (PCs) for highly efficient light trapping and controlling photonic devices in terms of tuned and controlled photonic bandgap (PBG) performance. We consider hyperbolic, exponential, and linear refractive index variation in the graded-index layer. We systematically study the influence of structural and grading parameters on the bandgap performance for two different graded photonic crystal (GPC) structures formed by stacking different graded-index layers. Compared with conventional PCs, the GPC bandgaps can be changed and tuned by the refractive index profile of the graded-index layer. We show that the number of bandgaps increases with the graded-index layer thickness and the bandgap frequencies can be tuned by the grading profiles. We observe the sequential increment in bandwidth for the complete PBGs in the GPC structures with linear, exponential, and hyperbolic graded-index materials. We also study the influence of the stacking pattern and grading profiles on the bandgap, phase shift, group velocity, delay time, and field distribution. The proposed GPC configurations facilitate the design of reflectors, multi-channel filters, detectors, and other photonic devices. The study may also provide the basis of understanding of the influence of graded-index materials on the PBG characteristics in the GPCs.

Rossby Waves Detection in the CO2 and Temperature Multilayer Climate Network

AbstractIncreasing atmospheric carbon dioxide (CO2) is the main factor of global warming. Carbon satellites have proven that CO2 concentrations have nonuniform spatio‐temporal distributions. The relationship between unevenly distributed CO2 and global surface air temperature (SAT) is seldom known. The success of complex networks provides an opportunity to address this issue. This paper proposes a multilayer climate network approach to identify the impacts of nonuniform CO2 on SAT. The results show that the probability density function (PDF) of degrees, weighted degrees, and link lengths follows power‐law distributions. A large fraction of strong correlation links resides in proximal distance (smaller than 2,000 km), indicating that CO2 nodes are strongly connected to the surrounding SAT nodes. The enhanced distributions of large positive weights, time delays, and degree patterns are all consistent with the properties of Rossby waves. This framework can be useful for predicting future climate changes and policy‐making for carbon reduction.

3Pa5-5 Effects of target scatterer size on ultrasonic sound velocity estimation based on delay time distribution

3Pa5-5 Effects of target scatterer size on ultrasonic sound velocity estimation based on delay time distribution

A strange star scenario for the formation of isolated millisecond pulsars

According to the recycling model, neutron stars in low-mass X-ray binaries were spun up to millisecond pulsars (MSPs), which indicates that all MSPs in the Galactic plane ought to be harbored in binaries. However, about 20% Galactic field MSPs are found to be solitary. To interpret this problem, we assume that the accreting neutron star in binaries may collapse and become a strange star when it reaches some critical mass limit. Mass loss and a weak kick induced by asymmetric collapse during the phase transition (PT) from neutron star to strange star can result in isolated MSPs. In this work, we use a population-synthesis code to examine the PT model. The simulated results show that a kick velocity of ∼60 km s−1 can produce ∼6 × 103 isolated MSPs and birth rate of ∼6.6 × 10−7 yr−1 in the Galaxy, which is approximately in agreement with predictions from observations. For the purpose of comparisons with future observation, we also give the mass distributions of radio and X-ray binary MSPs, along with the delay time distribution.

Measurements and simulations to investigate the feasibility of neutron multiplicity counting in the current mode of fission chambers

In two earlier papers [1], [2] we investigated the possibility of extracting traditional multiplicity count rates from the cumulants of fission chamber signals in current mode. It was shown that if all neutrons emitted from the sample simultaneously are also detected simultaneously, the multiplicity rates can be retrieved from the first three cumulants of the currents of up to three detectors, but the method breaks down if the detections of neutrons of common origin take place with a time delay spread wider than the pulse shape. To remedy these shortcomings, in this work we extended the theory to two- and three-point distributions (correlations). It was found thatthe integrals of suitably chosen two- and three-point moments with respect to the time differences become independent of the probability density of the time delays of detections. With this procedure, the multiplicity rates can be retrieved from the detector currents for arbitrary time delay distributions. To demonstrate the practical applicability of the proposed method, a measurement setup was designed and built. The statistics (shape and amplitude distribution) of the detector pulse were investigated as important parameters of the theoretical model. Simulations were performed to estimate the expected value of the multiplicity rates in the built setup. Measurements were performed and two types of moments (the mean and the covariance function) of the recorded detector signals were calculated. Values of singles rates were successfully recovered.

Stochastic Chemical Evolution of Radioactive Isotopes with a Monte Carlo Approach

Abstract Short-lived radionuclides (SLRs) with mean lives τ of a few to hundreds of Myr provide unique opportunities to probe recent nucleosynthesis events in the interstellar medium and the physical conditions in which the Sun formed. Here we quantify the uncertainty in the predicted evolution of SLRs within a parcel of interstellar gas given the stochastic nature of stellar enrichment events. We assume that an enrichment progenitor is formed at every time interval γ. For each progenitor, we randomly sample the delay time between its formation and its enrichment event, based on several delay-time distribution (DTD) functions that cover a wide range of astrophysical sites. For each set of τ, γ, and DTD functions, we follow the abundances of SLRs for 15 Gyr and repeat this process thousands of times to derive their probability distributions. For τ/γ ≳ 2, the distributions depend on the DTD function, and we provide tabulated values and analytical expressions to quantify the spread. The relative abundance uncertainty reaches a maximum of ∼60% for τ/γ = 1. For τ/γ ≲ 1, we provide the probability for the SLR abundance to carry the signature of only one enrichment event, which is greater than 50% when τ/γ ≲ 0.3. For 0.3 ≲ τ/γ ≲ 2, a small number of events contributed to the SLR abundance. This case needs to be investigated with a separate statistical method. We find that an isolation time for the birth of the Sun of roughly 9–13 Myr is consistent with the observed abundances of 60Fe, 107Pd, and 182Hf in the early solar system when assuming τ/γ ∼ 3 for these isotopes.

Gravitational-wave Sources from Mergers of Binary Black Holes Catalyzed by Flyby Interactions in the Field

Abstract Several scenarios were suggested for the origins of gravitational-wave (GW) sources from mergers of stellar binary black holes (BBHs). Here we propose a novel origin through catalyzed formation of GW sources from ultra-wide binaries in the field. Such binaries experience perturbations from random stellar flybys that excite their eccentricities. Once a wide binary is driven to a sufficiently small pericenter approach, GW emission becomes significant, and the binary inspirals and merges. We derive an analytic model and verify it with numerical calculation to compute the merger rate to be (f wide is the fraction of wide BH-binaries), which is a relevant contribution to the observationally inferred rate. The observational signatures from this channel include spin-orbit misalignment; preference for high mass ratio BBH; preference for high velocity dispersion host galaxies; and a uniform delay-time distribution.