arXiv subjects

Panagiota Kolitsidou

Publications and source records attributed to Panagiota Kolitsidou.

6 recordsLinked to original sources

arXiv2026

Parity symmetry as a diagnostic for spin-precessing binary-black-hole waveform models

Parity invariance of general relativity imposes exact relations between waveforms and remnant properties of binary-black-hole configurations related by reversal of the in-plane spins and observer direction. We summarize these relations and construct consistency tests for spin-precessing waveform and remnant models. Applying a conservative, unmaximized overlap diagnostic to seven state-of-the-art waveform models, we find that models built from aligned-spin calibrated waveforms and parity-covariant precession dynamics satisfy the symmetry to numerical precision. The original \texttt{IMRPhenomXO4a} and \texttt{IMRPhenomXPNR} implementations instead exhibit median parity residuals of approximately $1.6\times10^{-3}$ with broad upper tails, while \texttt{NRSur7dq4} shows its largest violations at high mass ratio and large spin magnitude. The asymmetric extension of \texttt{SEOBNRv5PHM} exhibits a smaller, localized violation, while \texttt{NRSur7dq4Remnant} shows larger residuals in the recoil than in the final mass and spin. We trace these violations to an observer-dependent phase anchor in the \texttt{IMRPhenom} antisymmetric mode, non-invariant parameterization of the \texttt{NRSur7dq4} surrogate fits, and one non-invariant NR-calibrated coefficient in the asymmetric \texttt{SEOBNRv5PHM} extension. Local corrections restore waveform parity to numerical precision for the \texttt{IMRPhenom} and \texttt{SEOBNRv5PHM} cases; restoring it in \texttt{NRSur7dq4} requires refitting the surrogate. Reanalyses of eight GWTC-5.0 events show no qualitative change in astrophysical interpretation, although the \texttt{IMRPhenom} correction yields Jensen-Shannon divergences up to $5\times10^{-2}$ in individual marginalized posteriors. Exact symmetries thus provide inexpensive, model-independent consistency tests and should be imposed by construction in calibrated waveform models.

gr-qc↗

arXiv2026

Identifying galactic binary systems of neutron stars and black holes with LISA

The Laser Interferometer Space Antenna (LISA) will detect $\sim 100$ galactic binary systems comprised of black holes and neutron stars. Distinguishing these binaries from the $\sim 10^4$ double white dwarfs detectable by LISA will be challenging. In the absence of any other information, the inferred component masses can be used to classify the nature of these objects. However, short-period galactic binaries $\sim 10^7$--$10^3\,\mathrm{yr}$ from coalescence produce a quasi-monochromatic signal which carries little information about their masses. We generate synthetic LISA data sets containing gravitational waves from Galactic binary black holes, binary neutron stars and black hole-neutron stars drawn from an astrophysically realistic population produced through the isolated binary evolution channel. We use a Bayesian inference pipeline to explore the accuracy with which the component masses can be measured. LISA will be able to infer component masses for $\approx 10\% - 50\%$ of the detected systems by measuring the orbital eccentricity, periapse precession frequency, and gravitational-wave induced frequency derivative. Typical fractional mass errors are $\approx 1\%$--$100\%$ (depending on the specific value of the source parameters) enabling the classification of the constituent objects as black holes or neutron stars. For these binaries, LISA will also be able to determine their 3-dimensional position in the Milky Way. LISA detections of these double compact objects will provide new insights to their astrophysical formation processes, the Galactic population, and the Milky Way's star formation history. However, for a significant fraction of the LISA-detected binaries the nature of their constituent objects may remain unclear.

astro-ph.HE↗

arXiv2024

Impact of anti-symmetric contributions to signal multipoles in the measurement of black-hole spins

Many current models for the gravitational-wave signal from precessing black-hole binaries neglect an asymmetry in the $\pm m$ multipoles. The asymmetry is weak, but is responsible for out-of-plane recoil, which for the final black hole can be several thousand km/s. In this work we show that the multipole asymmetry is also necessary to accurately measure the black-hole spins. We consider synthetic signals calculated from the numerical relativity surrogate model NRSur7dq4, which includes the multipole asymmetry, and measure the signal parameters using two versions of the same model, one with and one without the multipole asymmetry included. We find that in high signal-to-noise-ratio observations where the spin magnitude and direction can in principle be measured accurately, neglecting the multipole asymmetry can result in biased measurements of these quantities. Measurements of the black-hole masses and the standard aligned-spin combination $χ_{\rm eff}$ are not in general strongly affected. As an illustration of the impact of the multipole asymmetry on a real signal we consider the LVK observation GW200129_065458, and find that the inclusion of the multipole asymmetry is necessary to identify the binary as unequal-mass and a high in-plane spin in the primary.

gr-qc↗

arXiv2023

PhenomXO4a: a phenomenological gravitational-wave model for precessing black-hole binaries with higher multipoles and asymmetries

In this work we introduce PhenomXO4a, the first phenomenological, frequency-domain gravitational waveform model to incorporate multipole asymmetries and precession angles tuned to numerical relativity. We build upon the modeling work that produced the PhenomPNR model and incorporate our additions into the IMRPhenomX framework, retuning the coprecessing frame model and extending the tuned precession angles to higher signal multipoles. We also include, for the first time in frequency-domain models, a recent model for spin-precession-induced multipolar asymmetry in the coprecessing frame to the dominant gravitational-wave multipoles. The accuracy of the full model and its constituent components is assessed through comparison to numerical relativity and numerical relativity surrogate waveforms by computing mismatches and performing parameter estimation studies. We show that, for the dominant signal multipole, we retain the modeling improvements seen in the PhenomPNR model. We find that the relative accuracy of current full IMR models varies depending on location in parameter space and the comparison metric, and on average they are of comparable accuracy. However, we find that variations in the pointwise accuracy do not necessarily translate into large biases in the parameter estimation recoveries.

gr-qc↗

arXiv2023

First frequency-domain phenomenological model of the multipole asymmetry in gravitational-wave signals from binary-black-hole coalescence

Gravitational-wave signals from binaries that contain spinning black holes in general include an asymmetry between the $+m$ and $-m$ multipoles that is not included in most signal models used in LIGO-Virgo-KAGRA (LVK) analysis to date. This asymmetry manifests itself in out-of-plane recoil of the final black hole and its inclusion in signal models is necessary both to measure this recoil, but also to accurately measure the full spin information of each black hole. We present the first model of the anti-symmetric contribution to the dominant co-precessing-frame signal multipole throughout inspiral, merger and ringdown. We model the anti-symmetric contribution in the frequency domain, and take advantage of the approximations that the anti-symmetric amplitude can be modelled as a ratio of the (already modelled) symmetric amplitude, and analytic relationships between the symmetric and anti-symmetric phases during the inspiral and ringdown. The model is tuned to single-spin numerical-relativity simulations up to mass-ratio 8 and spin magnitudes of 0.8, and has been implemented in a recent phenomenological model for use in the fourth LVK observing run. However, the procedure described here can be easily applied to other time- or frequency-domain models.

gr-qc↗

arXiv2023

A catalogue of precessing black-hole-binary numerical-relativity simulations

We present a public catalogue of numerical-relativity binary-black-hole simulations. The catalogue contains datasets from 80 distinct configurations of precessing binary-black-hole systems, with mass ratios up to $m_2/m_1 = 8$, dimensionless spin magnitudes on the larger black hole up to $|\vec{S}_2|/m_2^2 = 0.8$ (the small black hole is non-spinning), and a range of five values of spin misalignment for each mass-ratio/spin combination. We discuss the physical properties of the configurations in our catalogue, and assess the accuracy of the initial configuration of each simulation and of the gravitational waveforms. We perform a careful analysis of the errors due to the finite resolution of our simulations and the finite distance from the source at which we extract the waveform data and provide a conservative estimate of the mismatch accuracy. We find that the upper limit on the mismatch uncertainty of our waveforms is $0.4\%$. In doing this we present a consistent approach to combining mismatch uncertainties from multiple error sources. We compare this release to previous catalogues and discuss how these new simulations complement the existing public datasets. In particular, this is the first catalogue to uniformly cover this parameter space of single-spin binaries and there was previously only sparse coverage of the precessing-binary parameter space for mass ratios $\gtrsim 5$. We discuss applications of these new data, and the most urgent directions for future simulation work. The public dataset can be accessed online at https://data.cardiffgravity.org/bam-catalogue/.

gr-qc↗