arXiv subjects

Alessandra Buonanno

Publications and source records attributed to Alessandra Buonanno.

At least 73 records · Page 4Linked to original sources

arXiv2022

Enriching the Symphony of Gravitational Waves from Binary Black Holes by Tuning Higher Harmonics

For the first time, we construct an inspiral-merger-ringdown waveform model within the effective-one-body formalism for spinning, nonprecessing binary black holes that includes gravitational modes beyond the dominant $(\ell,|m|) = (2,2)$ mode, specifically $(\ell,|m|)=(2,1),(3,3),(4,4),(5,5)$. Our multipolar waveform model incorporates recent (resummed) post-Newtonian results for the inspiral and information from 157 numerical-relativity simulations, and 13 waveforms from black-hole perturbation theory for the (plunge-)merger and ringdown. We quantify the improved accuracy including higher-order modes by computing the faithfulness of the waveform model against the numerical-relativity waveforms used to construct the model. We define the faithfulness as the match maximized over time, phase of arrival, gravitational-wave polarization and sky position of the waveform model, and averaged over binary orientation, gravitational-wave polarization and sky position of the numerical-relativity waveform. When the waveform model contains only the $(2,2)$ mode, we find that the averaged faithfulness to numerical-relativity waveforms containing all modes with $\ell \leq$ 5 ranges from $90\%$ to $99.9\%$ for binaries with total mass $20-200 M_\odot$ (using the Advanced LIGO's design noise curve). By contrast, when the $(2,1),(3,3),(4,4),(5,5)$ modes are also included in the model, the faithfulness improves to $99\%$ for all but four configurations in the numerical-relativity catalog, for which the faithfulness is greater than $98.5\%$. Using our results, we also develop also a (stand-alone) waveform model for the merger-ringdown signal, calibrated to numerical-relativity waveforms, which can be used to measure multiple quasi-normal modes. The multipolar waveform model can be extended to include spin-precession, and will be employed in upcoming observing runs of Advanced LIGO and Virgo.

gr-qc↗

arXiv2022

Snowmass White Paper: Gravitational Waves and Scattering Amplitudes

We review recent progress and future prospects for harnessing powerful tools from theoretical high-energy physics, such as scattering amplitudes and effective field theory, to develop a precise and systematically improvable framework for calculating gravitational-wave signals from binary systems composed of black holes and/or neutron stars. This effort aims to provide state-of-the-art predictions that will enable high-precision measurements at future gravitational-wave detectors. In turn, applying the tools of quantum field theory in this new arena will uncover theoretical structures that can transform our understanding of basic phenomena and lead to new tools that will further the cycle of innovation. While still in a nascent stage, this research direction has already derived new analytic results in general relativity, and promises to advance the development of highly accurate waveform models for ever more sensitive detectors.

hep-th↗

arXiv2022

Tests of General Relativity with Gravitational-Wave Observations using a Flexible--Theory-Independent Method

We perform tests of General Relativity (GR) with gravitational waves (GWs) from the inspiral stage of compact binaries using a theory-independent framework, which adds generic phase corrections to each multipole of a GR waveform model in frequency domain. This method has been demonstrated on LIGO-Virgo observations to provide stringent constraints on post-Newtonian predictions of the inspiral and to assess systematic biases that may arise in such parameterized tests. Here, we detail the anatomy of our framework for aligned-spin waveform models. We explore the effects of higher modes in the underlying signal on tests of GR through analyses of two unequal-mass, simulated binary signals similar to GW190412 and GW190814. We show that the inclusion of higher modes improves both the precision and the accuracy of the measurement of the deviation parameters. Our testing framework also allows us to vary the underlying baseline GR waveform model and the frequency at which the non-GR inspiral corrections are tapered off. We find that to optimize the GR test of high-mass binaries, comprehensive studies would need to be done to determine the best choice of the tapering frequency as a function of the binary's properties. We also carry out an analysis on the binary neutron-star event GW170817 to set bounds on the coupling constant $α_0$ of Jordan-Fierz-Brans-Dicke gravity. We take two plausible approaches; in the first \emph{theory-agnostic} approach we find a bound $α_0 \lesssim 2\times 10^{-1}$ from measuring the dipole-radiation for different neutron-star equations of state, while in the second \emph{theory-specific} approach we obtain $α_0 \lesssim 4\times 10^{-1}$, both at $68\%$ credible level. These differences arise mainly due to different statistical hypotheses used for the analysis.

gr-qc↗

arXiv2022

Effective-one-body multipolar waveforms for eccentric binary black holes with non-precessing spins

We construct an inspiral-merger-ringdown eccentric gravitational-wave (GW) model for binary black holes with non-precessing spins within the effective-one-body formalism. This waveform model, SEOBNRv4EHM, extends the accurate quasi-circular SEOBNRv4HM model to eccentric binaries by including recently computed eccentric corrections up to 2PN order in the gravitational waveform modes, notably the $(l,|m|)=(2,2),(2,1),(3,3),(4,4),(5,5)$ multipoles. The waveform model reproduces the zero eccentricity limit with an accuracy comparable to the underlying quasi-circular model, with the unfaithfulness of $\lesssim1\%$ against quasi-circular numerical-relativity (NR) simulations. When compared against 28 public eccentric NR simulations from the Simulating eXtreme Spacetimes catalog with initial orbital eccentricities up to $e\simeq0.3$ and dimensionless spin magnitudes up to $+0.7$, the model provides unfaithfulness $<1\%$, showing that both the $(2,|2|)$-modes and the higher-order modes are reliably described without calibration to NR datasets in the eccentric sector. The waveform model SEOBNRv4EHM is able to qualitatively reproduce the phenomenology of dynamical captures, and can be extended to include spin-precession effects. It can be employed for upcoming observing runs with the LIGO-Virgo-KAGRA detectors and used to re-analyze existing GW catalogs to infer the eccentricity parameters for binaries with $e\lesssim0.3$ (at 20 Hz or lower) and spins up to $\lesssim 0.9-0.95$. The latter is a promising region of the parameter space where some astrophysical formation scenarios of binaries predict mild eccentricity in the ground-based detectors' bandwidth. Assessing the accuracy and robustness of the eccentric waveform model SEOBNRv4EHM for larger eccentricities and spins will require comparisons with, and, likely, calibration to eccentric NR waveforms in a larger region of the parameter space.

gr-qc↗

arXiv2021

The Next Generation Global Gravitational Wave Observatory: The Science Book

The next generation of ground-based gravitational-wave detectors will observe coalescences of black holes and neutron stars throughout the cosmos, thousands of them with exceptional fidelity. The Science Book is the result of a 3-year effort to study the science capabilities of networks of next generation detectors. Such networks would make it possible to address unsolved problems in numerous areas of physics and astronomy, from Cosmology to Beyond the Standard Model of particle physics, and how they could provide insights into workings of strongly gravitating systems, astrophysics of compact objects and the nature of dense matter. It is inevitable that observatories of such depth and finesse will make new discoveries inaccessible to other windows of observation. In addition to laying out the rich science potential of the next generation of detectors, this report provides specific science targets in five different areas in physics and astronomy and the sensitivity requirements to accomplish those science goals. This report is the second in a six part series of reports by the GWIC 3G Subcommittee: i) Expanding the Reach of Gravitational Wave Observatories to the Edge of the Universe, ii) The Next Generation Global Gravitational Wave Observatory: The Science Book (this report), iii) 3G R&D: R&D for the Next Generation of Ground-based Gravitational Wave Detectors, iv) Gravitational Wave Data Analysis: Computing Challenges in the 3G Era, v) Future Ground-based Gravitational-wave Observatories: Synergies with Other Scientific Communities, and vi) An Exploration of Possible Governance Models for the Future Global Gravitational-Wave Observatory Network.

gr-qc↗

arXiv2021

Observing intermediate-mass black holes and the upper--stellar-mass gap with LIGO and Virgo

Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap $\sim 60-130~M_\odot$. Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing (O4) run, we perform Bayesian analysis on quasi-circular non-precessing, spinning IMBH binaries (IMBHBs) with total masses $50\mbox{--} 500\, M_\odot$, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at $2σ$, the mass of the heavier component of IMBHBs can be constrained with an uncertainty of $\sim 10-40\%$ at a signal-to-noise ratio of $20$. Focusing on the stellar-mass gap with new tabulations of the $^{12}\text{C}(α, γ)^{16} \text{O}$ reaction rate and its uncertanties, we evolve massive helium core stars using \MESA\, to establish the lower and upper edge of the mass gap as $\simeq$\,59$^{+34}_{-13}$\,$M_{\odot}$ and $\simeq$\,139$^{+30}_{-14}$\,$M_{\odot}$ respectively, where the error bars give the mass range that follows from the $\pm 3σ$ uncertainty in the $^{12}\text{C}(α, γ) ^{16} \text{O}$ nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we re-analyse GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90\% credibility.

gr-qc↗

arXiv2021

Conservative and radiative dynamics in classical relativistic scattering and bound systems

As recent work continues to demonstrate, the study of relativistic scattering processes leads to valuable insights and computational tools applicable to the relativistic bound-orbit two-body problem. This is particularly relevant in the post-Minkowskian approach to the gravitational two-body problem, where the field has only recently reached a full description of certain physical observables for scattering orbits, including radiative effects, at the third post-Minkowskian (3PM) order. As an historically instructive simpler example, we consider here the analogous problem in electromagnetism in flat spacetime. We compute for the first time the changes in linear momentum of each particle and the total radiated linear momentum, in the relativistic classical scattering of two point-charges, at sixth order in the charges (analogous to 3PM order in gravity). We accomplish this here via direct iteration of the classical equations of motion, while making comparisons where possible to results from quantum scattering amplitudes, with the aim of contributing to the elucidation of conceptual issues and scalability on both sides. We also discuss further extensions to radiative quantities of recently established relations which analytically continue certain observables from the scattering regime to the regime of bound orbits, applicable for both the electromagnetic and gravitational cases.

gr-qc↗

arXiv2021

Radiation-reaction force and multipolar waveforms for eccentric, spin-aligned binaries in the effective-one-body formalism

While most binary inspirals are expected to have circularized before they enter the LIGO/Virgo frequency band, a small fraction of those binaries could have non-negligible orbital eccentricity depending on their formation channel. Hence, it is important to accurately model eccentricity effects in waveform models used to detect those binaries, infer their properties, and shed light on their astrophysical environment. We develop a multipolar effective-one-body (EOB) eccentric waveform model for compact binaries whose components have spins aligned or anti-aligned with the orbital angular momentum. The waveform model contains eccentricity effects in the radiation-reaction force and gravitational modes through second post-Newtonian (PN) order, including tail effects, and spin-orbit and spin-spin couplings. We recast the PN-expanded, eccentric radiation-reaction force and modes in factorized form so that the newly derived terms can be directly included in the state-of-the-art, quasi-circular--orbit EOB model currently used in LIGO/Virgo analyses (i.e., the SEOBNRv4HM model).

gr-qc↗

arXiv2021

Constraints on quasi-normal-mode frequencies with LIGO-Virgo binary-black-hole observations

The no-hair conjecture in General Relativity (GR) states that a Kerr black hole (BH) is completely described by its mass and spin. As a consequence, the complex quasi-normal-mode (QNM) frequencies of a binary-black-hole (BBH) ringdown can be uniquely determined by the mass and spin of the remnant object. Conversely, measurement of the QNM frequencies could be an independent test of the no-hair conjecture. This paper extends to spinning BHs earlier work that proposed to test the no-hair conjecture by measuring the complex QNM frequencies of a BBH ringdown using parameterized inspiral-merger-ringdown waveforms in the effective-one-body formalism, thereby taking full advantage of the entire signal power and removing dependency on the predicted or estimated start time of the ringdown. Our method was used to analyze the properties of the merger remnants for BBHs observed by LIGO-Virgo in the first half of their third observing (O3a) run. After testing our method with GR and non-GR synthetic-signal injections in Gaussian noise, we analyze, for the first time, two BBHs from the first (O1) and second (O2) LIGO-Virgo observing runs, and two additional BBHs from the O3a run. We then provide joint constraints with published results from the O3a run. In the most agnostic and conservative scenario where we combine the information from different events using a hierarchical approach, we obtain, at $90\%$ credibility, that the fractional deviations in the frequency (damping time) of the dominant QNM are $δf_{220}=0.03^{+0.10}_{-0.09}$ ($δτ_{220}=0.10^{+0.44}_{-0.39}$), respectively, an improvement of a factor of $\sim 4$ ($\sim 2$) over the results obtained with our model in the LIGO-Virgo publication. The single-event most-stringent constraint to date continues to be GW150914 for which we obtain $δf_{220}=0.05^{+0.11}_{-0.07}$ and $δτ_{220}=0.07^{+0.26}_{-0.23}$.

gr-qc↗

arXiv2021

A detailed analysis of GW190521 with phenomenological waveform models

In this paper we present an extensive analysis of the GW190521 gravitational wave event with the current (fourth) generation of phenomenological waveform models for binary black hole coalescences. GW190521 stands out from other events since only a few wave cycles are observable. This leads to a number of challenges, one being that such short signals are prone to not resolve approximate waveform degeneracies, which may result in multi-modal posterior distributions. The family of waveform models we use includes a new fast time-domain model IMRPhenomTPHM, which allows us extensive tests of different priors and robustness with respect to variations in the waveform model, including the content of spherical harmonic modes. We clarify some issues raised in a recent paper [Nitz&Capano], associated with possible support for a high-mass ratio source, but confirm their finding of a multi-modal posterior distribution, albeit with important differences in the statistical significance of the peaks. In particular, we find that the support for both masses being outside the PISN mass-gap, and the support for an intermediate mass ratio binary are drastically reduced with respect to what Nitz&Capano found. We also provide updated probabilities for associating GW190521 to the potential electromagnetic counterpart from ZTF.

gr-qc↗

arXiv2021

Fast post-adiabatic waveforms in the time domain: Applications to compact binary coalescences in LIGO and Virgo

We present a computationally efficient (time-domain) multipolar waveform model for quasi-circular spin-aligned compact binary coalescences. The model combines the advantages of the numerical-relativity informed, effective-one-body (EOB) family of models with a post-adiabatic solution of the equations of motion for the inspiral part of the two-body dynamics. We benchmark this model against other state-of-the-art waveforms in terms of efficiency and accuracy. We find a speed-up of one to two orders of magnitude compared to the underlying time-domain EOB model for the total mass range $2 - 100 M_{\odot}$. More specifically, for a low total-mass system, such as a binary neutron star with equal masses of $1.4 M_{\odot}$, like GW170817, the computational speedup is around 100 times; for an event with total mass $\sim 40 M_\odot$ and mass ratio $\sim 3$, like GW190412, the speedup is by a factor of $\sim 20$, while for a binary system of comparable masses and total mass of $\sim 70 M_{\odot}$, like GW150914, it is by a factor of $\sim 10$. We demonstrate that the new model is extremely faithful to the underlying EOB model with unfaithfulness less than $0.01\%$ across the entire applicable region of parameter space. Finally, we present successful applications of this new waveform model to parameter estimation studies and tests of general relativity.

gr-qc↗

arXiv2021

An aligned-spin neutron-star--black-hole waveform model based on the effective-one-body approach and numerical-relativity simulations

After the discovery of gravitational waves from binary black holes (BBHs) and binary neutron stars (BNSs) with the LIGO and Virgo detectors, neutron-star--black-holes (NSBHs) are the natural next class of binary systems to be observed. In this work, we develop a waveform model for aligned-spin neutron-star--black-holes (NSBHs) combining a BBH baseline waveform (available in the effective-one-body approach) with a phenomenological description of tidal effects (extracted from numerical-relativity simulations), and correcting the amplitude during the late inspiral, merger and ringdown to account for the NS tidal disruption. We calibrate the amplitude corrections using NSBH waveforms obtained with the SpEC and the SACRA codes. The model was calibrated using simulations with NS masses in the range $1.2-1.4 M_\odot$, tidal deformabilities up to $4200$ (for a 1.2 $M_\odot$ NS), and dimensionless BH spin magnitude up to 0.9. Based on the simulations used, and on checking that sensible waveforms are produced, we recommend our model to be employed with NS mass in the range $1\mbox{--}3 M_\odot$, tidal deformability $0\mbox{--}5000$, and BH spin magnitude up to $0.9$. We also validate our model against two new, highly accurate NSBH waveforms with BH spin 0.9 and mass ratios 3 and 4, characterized by tidal disruption, produced with SpEC, and find very good agreement. We find that it will be challenging for the advanced LIGO-Virgo--detector network at design sensitivity to distinguish different source classes. We perform parameter-estimation on a synthetic numerical-relativity signal in zero noise to study parameter biases. Finally, we reanalyze GW170817, with the hypothesis that it is a NSBH. We do not find evidence to distinguish the BNS and NSBH hypotheses, however the posterior for the mass ratio is shifted to less equal masses under the NSBH hypothesis. [Abstract abridged for arxiv].

gr-qc↗

arXiv2020

Gravitational-Wave Constraints on an Effective Field-Theory Extension of General Relativity

Gravitational-wave observations of coalescing binary systems allow for novel tests of the strong-field regime of gravity. Using data from the Gravitational Wave Open Science Center (GWOSC) of the LIGO and Virgo detectors, we place the first constraints on an effective field-theory based extension of General Relativity in which only higher-order curvature terms are added to the Einstein-Hilbert action. We construct gravitational-wave templates describing the quasi-circular, adiabatic inspiral phase of binary black holes in this extended theory of gravity. Then, after explaining how to properly take into account the region of validity of the effective field theory when performing tests of General Relativity, we perform Bayesian model selection using the two lowest-mass binary black-hole events reported to date by LIGO and Virgo -- GW151226 and GW170608 -- and constrain this theory with respect to General Relativity. We find that these data disfavors the appearance of new physics on distance scales around $\sim 150$ km. Finally, we describe a general strategy for improving constraints as more observations will become available with future detectors on the ground and in space.

gr-qc↗

arXiv2020

Fourth post-Newtonian effective-one-body Hamiltonians with generic spins

In a compact binary coalescence, the spins of the compact objects can have a significant effect on the orbital motion and gravitational-wave (GW) emission. For generic spin orientations, the orbital plane precesses, leading to characteristic modulations of the GW signal. The observation of precession effects is crucial to discriminate among different binary formation scenarios, and to carry out precise tests of General Relativity. Here, we work toward an improved description of spin effects in binary inspirals, within the effective-one-body (EOB) formalism, which is commonly used to build waveform models for LIGO and Virgo data analysis. We derive EOB Hamiltonians including the complete fourth post-Newtonian (4PN) conservative dynamics, which is the current state of the art. We place no restrictions on the spin orientations or magnitudes, or on the type of compact object (e.g., black hole or neutron star), and we produce the first generic-spin EOB Hamiltonians complete at 4PN order. We consider multiple spinning EOB Hamiltonians, which are more or less direct extensions of the varieties found in previous literature, and we suggest another simplified variant. Finally, we compare the circular-orbit, aligned-spin binding-energy functions derived from the EOB Hamiltonians to numerical-relativity simulations of the late inspiral. While finding that all proposed Hamiltonians perform reasonably well, we point out some interesting differences, which could guide the selection of a simpler, and thus faster-to-evolve EOB Hamiltonian to be used in future LIGO and Virgo inference studies.

gr-qc↗

arXiv2020

Multipolar Effective-One-Body Waveforms for Precessing Binary Black Holes: Construction and Validation

As gravitational-wave detectors become more sensitive, we will access a greater variety of signals emitted by compact binary systems, shedding light on their astrophysical origin and environment. A key physical effect that can distinguish among formation scenarios is the misalignment of the spins with the orbital angular momentum, causing the spins and the binary's orbital plane to precess. To accurately model such systems, it is crucial to include multipoles beyond the dominant quadrupole. Here, we develop the first multipolar precessing waveform model in the effective-one-body (EOB) formalism for the inspiral, merger and ringdown (IMR) of binary black holes: SEOBNRv4PHM. In the nonprecessing limit, the model reduces to SEOBNRv4HM, which was calibrated to numerical-relativity (NR) simulations, and waveforms from perturbation theory. We validate SEOBNRv4PHM by comparing it to the public catalog of 1405 precessing NR waveforms of the Simulating eXtreme Spacetimes (SXS) collaboration, and also to new 118 precessing NR waveforms, which span mass ratios 1-4 and spins up to 0.9. We stress that SEOBNRv4PHM is not calibrated to NR simulations in the precessing sector. We compute the unfaithfulness against the 1523 SXS precessing NR waveforms, and find that, for $94\%$ ($57\%$) of the cases, the maximum value, in the total mass range $20-200 M_\odot$, is below $3\%$ ($1\%$). Those numbers become $83\%$ ($20\%$) when using the IMR, multipolar, precessing phenomenological model IMRPhenomPv3HM. We investigate the impact of such unfaithfulness values with two parameter-estimation studies on synthetic signals. We also compute the unfaithfulness between those waveform models and identify in which part of the parameter space they differ the most. We validate them also against the multipolar, precessing NR surrogate model NRSur7dq4, and find that the SEOBNRv4PHM model outperforms IMRPhenomPv3HM.

gr-qc↗

arXiv2019

Theory-agnostic framework for dynamical scalarization of compact binaries

Gravitational wave observations can provide unprecedented insight into the fundamental nature of gravity and allow for novel tests of modifications to General Relativity. One proposed modification suggests that gravity may undergo a phase transition in the strong-field regime; the detection of such a new phase would constitute a smoking-gun for corrections to General Relativity at the classical level. Several classes of modified gravity predict the existence of such a transition - known as spontaneous scalarization - associated with the spontaneous symmetry breaking of a scalar field near a compact object. Using a strong-field-agnostic effective-field-theory approach, we show that all theories that exhibit spontaneous scalarization can also manifest dynamical scalarization, a phase transition associated with symmetry breaking in a binary system. We derive an effective point-particle action that provides a simple parametrization describing both phenomena, which establishes a foundation for theory-agnostic searches for scalarization in gravitational-wave observations. This parametrization can be mapped onto any theory in which scalarization occurs; we demonstrate this point explicitly for binary black holes with a toy model of modified electrodynamics.

gr-qc↗

arXiv2019

On the properties of the massive binary black hole merger GW170729

We present a detailed investigation into the properties of GW170729, the gravitational wave with the most massive and distant source confirmed to date. We employ an extensive set of waveform models, including new improved models that incorporate the effect of higher-order waveform modes which are particularly important for massive systems. We find no indication of spin-precession, but the inclusion of higher-order modes in the models results in an improved estimate for the mass ratio of $(0.3-0.8)$ at the 90\% credible level. Our updated measurement excludes equal masses at that level. We also find that models with higher-order modes lead to the data being more consistent with a smaller effective spin, with the probability that the effective spin is greater than zero being reduced from $99\%$ to $94\%$. The 90\% credible interval for the effective spin parameter is now $(-0.01-0.50)$. Additionally, the recovered signal-to-noise ratio increases by $\sim0.3$ units compared to analyses without higher-order modes. We study the effect of common spin priors on the derived spin and mass measurements, and observe small shifts in the spins, while the masses remain unaffected. We argue that our conclusions are robust against systematic errors in the waveform models. We also compare the above waveform-based analysis which employs compact-binary waveform models to a more flexible wavelet- and chirplet-based analysis. We find consistency between the two, with overlaps of $\sim 0.9$, typical of what is expected from simulations of signals similar to GW170729, confirming that the data are well-described by the existing waveform models. Finally, we study the possibility that the primary component of GW170729 was the remnant of a past merger of two black holes and find this scenario to be indistinguishable from the standard formation scenario.

gr-qc↗

arXiv2019

Extreme Gravity and Fundamental Physics

Future gravitational-wave observations will enable unprecedented and unique science in extreme gravity and fundamental physics answering questions about the nature of dynamical spacetimes, the nature of dark matter and the nature of compact objects.

astro-ph.HE↗