Gravitational waves emitted by neutron star black hole mergers encode key properties of neutron stars-such as their size, maximum mass, and spins-and black holes. However, it is challenging to ...generate accurate waveforms from these systems with numerical relativity, and not much is known about systematic uncertainties due to waveform modeling. We simulate gravitational waves from neutron star black hole mergers by hybridizing numerical relativity waveforms produced with the SpEC code with a recent numerical relativity surrogate NRHybSur3dq8Tidal. These signals are analyzed using a range of available waveform families, and statistical and systematic errors are reported. We find that at a network signal-to-noise ratio (SNR) of 30, statistical uncertainties are usually larger than systematic offsets, while at an SNR of 70, the two become comparable. The individual black hole and neutron star masses, as well as the mass ratios, are typically measured very precisely, though not always accurately at high SNR. At an SNR of 30, the neutron star tidal deformability can only be bound from above, while for louder sources, it may be measured and constrained away from zero. All neutron stars in our simulations are nonspinning, but in no case can we constrain the neutron star spin to be smaller than ~ 0.4 (90% credible interval). At lower mass ratios, waveform families whose late inspiral has been tuned specifically for neutron star black hole signals typically yield the most accurate characterization of the source parameters. Their measurements are in tension with those obtained using waveform families tuned against binary neutron stars, even for mass ratios that could be relevant for both binary neutron stars and neutron star black holes mergers. At higher mass ratios, waveforms that account for higher order modes yield the best results.
The final black hole left behind after a binary black hole merger can attain a recoil velocity, or a "kick," reaching values up to 5000 km/s. This phenomenon has important implications for ...gravitational wave astronomy, black hole formation scenarios, testing general relativity, and galaxy evolution. We consider the gravitational wave signal from the binary black hole merger GW200129_065458 (henceforth referred to as GW200129), which has been shown to exhibit strong evidence of orbital precession. Using numerical relativity surrogate models, we constrain the kick velocity of GW200129 to v_{f}∼1542_{-1098}^{+747} km/s or v_{f}≳698 km/s (one-sided limit), at 90% credibility. This marks the first identification of a large kick velocity for an individual gravitational wave event. Given the kick velocity of GW200129, we estimate that there is a less than 0.48% (7.7%) probability that the remnant black hole after the merger would be retained by globular (nuclear star) clusters. Finally, we show that kick effects are not expected to cause biases in ringdown tests of general relativity for this event, although this may change in the future with improved detectors.
Abstract The collection of gravitational waves (GWs) that are either too weak or too numerous to be individually resolved is commonly referred to as the gravitational-wave background (GWB). A ...confident detection and model-driven characterization of such a signal will provide invaluable information about the evolution of the universe and the population of GW sources within it. We present a new, user-friendly, Python-based package for GW data analysis to search for an isotropic GWB in ground-based interferometer data. We employ cross-correlation spectra of GW detector pairs to construct an optimal estimator of the Gaussian and isotropic GWB, and Bayesian parameter estimation to constrain GWB models. The modularity and clarity of the code allow for both a shallow learning curve and flexibility in adjusting the analysis to one’s own needs. We describe the individual modules that make up pygwb , following the traditional steps of stochastic analyses carried out within the LIGO, Virgo, and KAGRA Collaboration. We then describe the built-in pipeline that combines the different modules and validate it with both mock data and real GW data from the O3 Advanced LIGO and Virgo observing run. We successfully recover all mock data injections and reproduce published results.
Abstract
The population-level distributions of the masses, spins, and redshifts of binary black holes (BBHs) observed using gravitational waves can shed light on how these systems form and evolve. ...Because of the complex astrophysical processes shaping the inferred BBH population, models allowing for correlations among these parameters will be necessary to fully characterize these sources. We hierarchically analyze the BBH population detected by LIGO and Virgo with a model allowing for correlations between the effective aligned spin and the primary mass and redshift. We find that the width of the effective spin distribution grows with redshift at 98.6% credibility. We determine this trend to be robust under the application of several alternative models and additionally verify that such a correlation is unlikely to be spuriously introduced using a simulated population. We discuss the possibility that this correlation could be due to a change in the natal black hole spin distribution with redshift.
Abstract
Compact-object binary mergers consisting of one neutron star and one black hole (NSBHs) have long been considered promising progenitors for gamma-ray bursts, whose central engine remains ...poorly understood. Using gravitational-wave constraints on the population-level NSBH mass and spin distributions we find that at most 20 Gpc
−3
yr
−1
of gamma-ray bursts in the local universe can have NSBH progenitors.
Abstract
The Wide-Field Infrared Transient Explorer (WINTER) is a new 1 deg
2
seeing-limited time-domain survey instrument designed for dedicated near-infrared follow-up of kilonovae from binary ...neutron star (BNS) and neutron star–black hole mergers. WINTER will observe in the near-infrared
Y
,
J
, and short-
H
bands (0.9–1.7
μ
m, to
J
AB
= 21 mag) on a dedicated 1 m telescope at Palomar Observatory. To date, most prompt kilonova follow-up has been in optical wavelengths; however, near-infrared emission fades more slowly and depends less on geometry and viewing angle than optical emission. We present an end-to-end simulation of a follow-up campaign during the fourth observing run (O4) of the LIGO, Virgo, and KAGRA interferometers, including simulating 625 BNS mergers, their detection in gravitational waves, low-latency and full parameter estimation skymaps, and a suite of kilonova lightcurves from two different model grids. We predict up to five new kilonovae independently discovered by WINTER during O4, given a realistic BNS merger rate. Using a larger grid of kilonova parameters, we find that kilonova emission is ≈2 times longer lived and red kilonovae are detected ≈1.5 times further in the infrared than in the optical. For 90% localization areas smaller than 150 (450) deg
2
, WINTER will be sensitive to more than 10% of the kilonova model grid out to 350 (200) Mpc. We develop a generalized toolkit to create an optimal BNS follow-up strategy with any electromagnetic telescope and present WINTER’s observing strategy with this framework. This toolkit, all simulated gravitational-wave events, and skymaps are made available for use by the community.
The growing catalog of gravitational-wave signals from compact object mergers has allowed us to study the properties of black holes and neutron stars more precisely than ever before and has opened a ...new window through which to probe the earliest moments in our universe’s history. Population-level measurements of the masses and spins of compact objects can reveal how these systems form and evolve. Multi- messenger observations of compact object mergers can shed light on the properties of the electromagnetic counterparts of these systems, such as short gamma-ray bursts and kilonovae. Finally, observations of the stochastic gravitational-wave background can constrain early-universe physics inaccessible with other means. In this thesis, I demonstrate how we can leverage such observations of gravitational waves and their electromagnetic counterparts to learn about astrophysics and cosmology. The first part focuses on methods for facilitating the detection of electromagnetic counterparts and the simultaneous analysis of gravitational-wave and electromagnetic data for mergers including a neutron star. I then transition to a detailed study of black hole spin, including characterizing the measurability of spin in individual systems with current gravitational-wave detectors and presenting novel population-level analyses. This work is complemented by the development of new methods for increasingly detailed gravitational-wave data analysis. Such analyses will be critical to the astrophysical interpretation of the growing catalog of compact-object binaries and will enable the future detection of the cosmological stochastic gravitational-wave background.
Abstract GW230529 is the first compact binary coalescence detected by the LIGO–Virgo–KAGRA collaboration with at least one component mass confidently in the lower mass gap, corresponding to the range ...3–5 M ⊙ . If interpreted as a neutron star–black hole merger, this event has the most symmetric mass ratio detected so far and therefore has a relatively high probability of producing electromagnetic (EM) emission. However, no EM counterpart has been reported. At the merger time t 0 , Swift-BAT and Fermi-GBM together covered 100% of the sky. Performing a targeted search in a time window t 0 − 20 s, t 0 + 20 s, we report no detection by the Swift-BAT and Fermi-GBM instruments. Combining the position-dependent γ -ray flux upper limits and the gravitational-wave posterior distribution of luminosity distance, sky localization, and inclination angle of the binary, we derive constraints on the characteristic luminosity and structure of the jet possibly launched during the merger. Assuming a top-hat jet structure, we exclude at 90% credibility the presence of a jet that has at the same time an on-axis isotropic luminosity ≳10 48 erg s −1 in the bolometric band 1 keV–10 MeV and a jet opening angle ≳15°. Similar constraints are derived by testing other assumptions about the jet structure profile. Excluding GRB 170817A, the luminosity upper limits derived here are below the luminosity of any GRB observed so far.
The astrophysical formation channels of binary black hole systems predict correlations between their mass, spin, and redshift distributions, which can be probed with gravitational-wave observations. ...Population-level analysis of the latest LIGO-Virgo-KAGRA catalog of binary black hole mergers has identified evidence for such correlations assuming linear evolution of the mean and width of the effective spin distribution as a function of the binary mass ratio and merger redshift. However, the complex astrophysical processes at play in compact binary formation do not necessarily predict linear relationships between the distributions of these parameters. In this work, we relax the assumption of linearity and instead search for correlations using a more flexible cubic spline model. Our results suggest a nonlinear correlation between the width of the effective spin distribution and redshift. We also show that the LIGO-Virgo-Kagra collaborations may find convincing Bayesian evidence for nonlinear correlations by the end of the fourth observing run, O4. This highlights the valuable role of flexible models in population analyses of compact-object binaries in the era of growing catalogs.
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